ENGIN. 
 LIBRARY 
 
 UC-NRLF 
 
 STANDARD 
 INSTRUM 
 
 nr 
 Ui 
 
 NTS 
 
 C. L. BERGER &. SONS 
 
 Sf WM.MAM* STMKCT. 
 
 Boston^Mass, U.S.A. 
 
*Kl*lfl?V* 
 
 All persons infringing on the Patent Rights of our instruments or Copyright of this Ca^Bgufr^ ^ 
 and Price List will be prosecuted to the extent of the law. ***/ 
 
 Engineering 
 
 Prices This Catalogue and Price List supersedes all former editions. 
 We make no deduction from Catalogue Prices. 
 
 Payments Customers ordering from a distance will please remit by 
 registered letter, express or P. O. money order, or draft, made payable to 
 us, or tne goods win be sent C. O.D.,the expense of collection to be borne 
 by the purchaser. Accounts can only be opened with firms rated by com- 
 mercial agencies or upon receipt of other satisfactory reference. 
 
 Ordering When goods are ordered by telegraph our code should be used 
 exclusively (see back pages of catalogue), and then patrons (excepting 
 states municipalities, corporations, etc.) who are not known to us should 
 also wire simultaneously whether goods are to be sent C.O.D. or whether 
 payment is secured by bank draft on Boston or New York. (SEE "PAY- 
 MENTS," PAGE M OF CODE.) The order shojuld then be confirmed by let- 
 ter. 
 
 Address Please be careful to add the COUNTY and STATE to your ad- 
 dress. 
 
 Mail Orders Small articles can be sent by mail, at the purchaser's risk, 
 when the cost of postage, one cent for every ounce, is remitted in addition 
 to the price. 
 
 Shipping Our instruments are carefully packed in their boxes, which 
 again are placed in packing boxes, as explained under "Transportation of 
 Instruments" page 18. This insures safest delivery; and being in con- 
 formity with the rules of most of the large Express Companies, also en- 
 ables us to express Surveying Instruments as merchandise, thus secur- 
 ing to our customers single rates. 
 
 Cable Address, BERGER, Boston. 
 
PREFACE. 
 
 THE instruments enumerated in this catalog, and described in the Manual, are all 
 of our own design and regular manufacture. Full supplies of Engineers' and 
 Surveyors' Instruments will be kept on hand. The demand is at times so great, 
 however, as to exhaust our supply. To secure an instrument in season, it is best to 
 order it from four to eight weeks in advance of its intended use. Instruments varying 
 from our customary designs, or those of rare inquiry, will be made to order only. 
 
 The mechanical features of our instruments are of the most simple 
 and mechanically perfect design and the best that modern machinery and methods 
 pursued in a most modern plant, equipped and operated wholly for this purpose, can 
 produce. 
 
 The graduations of circles and verniers, being sharp, clean cut and 
 easily read, are of rare excellence and in point of accuracy have no superior. 
 
 The optical qualities of our telescopes are in keeping with the fine- 
 ness of every other part of the instruments in higher power permissible with greatest 
 illumination and sharpest definition. 
 
 The spirit levels ground and used by us are selected in degree of sensitiveness 
 so as to be strictly related to the whole character of the instruments. 
 
 A careful perusal of our catalog- will convince that in the number of 
 styles, sizes, new designs, and in the adaptation of the various instruments to the work 
 for which they are intended, we offer instruments that only long training and a studi- 
 ous care of the needs of the engineering and surveying profession in all lines of practi- 
 cal application in the field, can produce. 
 
 Styles and sizes of the many kinds of instruments enumerated in this catalog 
 cannot be varied from, since all the standard patterns from which the different parts 
 are cast are made of brass to insure best and uniform results. Any change from them 
 often would entail only extra expense, and lead to the sacrifice of other and equally 
 important advantages, without securing to the customer any material benefit. 
 
 The combinations possible with each particular type of instrument are printed on 
 the page opposite its cut, and as a rule are so complete as to meet special and general 
 requirements. 
 
 We make no pretence at manufacturing cheap instruments our prices are 
 as low as consistent with thoroughness of workmanship and the use of the best mate- 
 rials. The aim of the firm in the future will be, as it has been since originally organ- 
 ized by the senior member in 1871, to create an American industry in the art of mak- 
 ing field instruments unsurpassed either here or abroad, bringing to the task the 
 judgment and experience of maturity. 
 
 Our full telegraphic Code, at back of this catalog, will enable to order 
 from a distance at small expense, and our patrons may rely upon being served as con- 
 scientiously as if calling upon us in person. 
 
 take this opportunity to thank our patrons for their confidence in the 
 past, and assure them that their future orders will be executed with the same care and 
 fidelity as heretofore. 
 
 C. L. BERGER & SONS. 
 
 80029O 
 
TRAKSTSZ3/LEVELS 
 
 CHARACTERISTIC FEATURES 
 OF OUR INSTRUMENTS 
 
 1. Simplicity in Manipulation. 
 
 2. Lightness, combined with strength* 
 
 3. Accuracy of division. 
 
 4. Achromatic telescope, with high power. 
 
 5. Steadiness of adjustments under varying tempera- 
 
 tures. 
 
 6. Stiffness; to avoid any tremor even in a strong 
 
 wind. 
 
 7. Fine workmanship throughout. 
 
 8. Adapted to tropical and arctic conditions. 
 
 9. Prices EQUITABLE ! 
 
DESCRIPTION 
 
 OP THE 
 
 Essential Features of Our Instruments. 
 
 Graduation. 
 
 This very important part of a good instrument we guarantee exact and accurately 
 centered, opposite verniers reading the same. The lines are straight, thoroughly 
 black and uniform in width. There are two double verniers in every transit to read 
 angles with great rapidity as well as to make four separate readings at every sight, 
 when extreme accuracy in the repetition of angles is required. The horizontal 
 circle is graduated from to 360 with two sets of tigures, running in opposite 
 directions ( unless ordered differently,) and the verniers are marked A and B . The 
 figures are large and distinct, and to avoid mistakes in reading, the figures of these 
 two sets of graduations, and those on the verniers, are inclined in opposite directions, 
 thus indicating the directions in which the verniers should be read. 
 
 Instruments intended for mining and mountain use can have the verniers so 
 placed that they may be read without changing the position of the engineer after 
 sighting through the telescope. 
 
 Glass covers protect the arc and verniers from exposure. For ease in reading 
 the verniers, we have added to most of our instruments two plates of ground glass, 
 which cast a very clear light on the verniers, in any position. We recommend this 
 addition to all of our more complete transits. 
 
 The graduations on our transits are either on brass and silvered, or else gradu- 
 ated on solid silver. The former we can only recommend for the more ordinary 
 instruments, since imperfections in the brass or composition castings frequently 
 impair the graduations, and the silvering is apt to tarnish with time and exposure. 
 
 To graduate on solid silver adds $10 to the first outlay for the instrument, but its 
 many advantages, great permanency and smoothness of surface render it the only 
 satisfactory surface for fine graduations. 
 
 The Telescope. 
 
 All of its lenses are ground especially for us, by the best opticians. The teles- 
 cope is perfectly achromatic, and designed to furnish a large, flat field of view with 
 high power and yet without loss of light. For this purpose the curves of all our 
 lenses are ground by special formulae. The telescopes show objects right side 
 up, unless ordered otherwise. 
 
 The object-glass has a very large aperture, and is focussed by rack and pinion,f 
 but the eye-piece is focussed by simply turning its head to the right or left in an 
 improved screw-like manner. 
 
 By a method of construction peculiar to ourselves, we are enabled to guarantee 
 the line of collimation correct for all distances without making use of the very objec- 
 tionable adjustment for the object-slide by means of inner rings, which time and 
 experience has proven to wear loose too readily, thus rendering this adjustment 
 worse than none at all. 
 
 The eye-pieces are thoroughly achromatic, and their lenses are mounted in such 
 a perfect manner (a method also peculiar to us) as to require no further adjustment 
 with regard to the axis of telescope. 
 
 *It should be remembered that the focal length of the object glass is limited in engineering instruments and 
 that a high power is obtained only at the sacrifice of light. To obtain the fullest satisfaction, telescopes intend- 
 ed for close work, as in stadia measurement, etc., should invariably be ordered to be inverting. Th 
 brilliancy with which objects appear in such a telescope, owing to the amount of light gained by 
 saving two lenses in the eve-piece is vary marked as compared with one of the same power and focal length 
 showing objects erect. 
 
 tThis rack and pinion motion is now so placed upon our telescopes that it is more easy of access by either 
 hand than when placed at the side, as shown in most of our cuts. 
 
The telescope of the transit reverses at both the eye and object ends, and is 
 thoroughly balanced when focussed for a mean distance. 
 
 The telescope of the wye and dumpy level is also balanced each way from the 
 center of the vertical axis when focussed for mean distance and with the sun-shade 
 attached to it. 
 
 Spirit-Le vels . 
 
 The Spirit Levels used in our instruments are carefully ground, filled and tested 
 by us in person. 
 
 Those for the highest class of engineering work are sometimes provided with an 
 air chamber by which the length of the bubble can be regulated according to tem- 
 perature. The levels for astronomical instruments have air chambers, and are tilled 
 with ether, but in field instruments ether is not admissable, owing to the high 
 degree of expansion and contraction in that fluid with changes of temperature. 
 For these we use a composition fluid that we have found to be more sensitive and 
 quick-acting than that used in instruments we have seen of other makers. 
 
 Our astronomical levels are so ground that a depression through one second of 
 arc causes a displacement of the bubble through about ^ of an inch. The curva- 
 ture or sensitiveness of our levels for field instruments we adapt carefully to the 
 instruments and the kind of work to which they are to be applied. With too sen- 
 sitive a level the position of the bubble would be too uneasy to work with, while 
 too low a sensitiveness would not reveal the firll qualities of an instrument. Persons 
 ordering instruments of us will confer a favor by stating for what purpose they are 
 intended, whether for water works, for railroads, or for general use, so that we 
 can use our judgment for their benefit. 
 
 Gradienter Screw. 
 
 [Seepage 45] 
 
 This is attached to the clamp of telescope of all of our transits except the plain 
 transit. This attachment was first introduced ty Prof. Stampfer, of the Vienna 
 Polytechnic School. It does not add to the weight of the instrument, and once 
 used we have found it to be universally approved by our customers. By means of 
 it grades can be established, and horizontal distances, vertical angles and differences 
 of level can be measured with great rapidity. Indeed this attachment to an en- 
 gineer's transit is one of the most useful introductions in practical engineering. 
 It is so universal in its application to railroad and general work, that when once 
 used it will afterwards form an indispensible part of an engineer's outfit. 
 
 Fixed Stadia Wires for Distance Measurements. 
 
 We have specially devised an optical and mechanical apparatus for the purpose 
 of placing fixed, or non-adjustable stadia wires so accurately upon the diaphragms 
 of our telescopes that their distance apart will read 1' : 100" f on any leveling rod, 
 as with the gradienter screw, thus dispensing with a special rod. 
 
 It is well known that adjustable stadia wires are so apt to change their distance 
 apart with every change of temperature, that no reliance can be placed upon them 
 unless previously adjusted. With fixed stadia wires, annoyances of this kind are 
 obviated they are reliable at all times. 
 
 As regards the degree of accuracy attainable by the use of fixed stadia wires, 
 experiments with our powerful telescopes, made optically as perfect as the most 
 advanced optical and mechanical skill enables us, warrant to say that with some 
 experience and proper care the results obtained will approximate and even equal 
 those obtained by chain measurements. The price for this accessory in any new 
 instrument is only $3.00, but if inserted into a telescope sent to us for that purpose, 
 we must charge $10.00. We advise to order both the gradienter screw and the 
 fixed stadia wires, as each in itself, separately or jointly, will prove of great value. 
 
 t In all stadia work, the instrument constant, which is the distance from the center of the instru- 
 ment to a point in front of the object-glass equal to its focal length, must be added to every measurement, 
 whether 100 or 1000 feet, and does not vary. 
 
 Instrument Constant for 
 
 Transit Nos. 1, 5 and 11 erect telescope 1.15 ft. 
 
 " " " " " invert. " i-37 " 
 
 Transit Nos. 2, 3 and 6 erect .04 " 
 
 Transit No. 4 erect " .74 
 
 Transit No. 4 invert, telescope .88 ft 
 
 Wye Level, 18-inch erect " 1.90 " 
 invert. 2.14" 
 
 Wye Level, 14-inch erect " 1.41" 
 
 Dumpy Level, 17% inch erect " 1.65" 
 Dumpy Level, 15-inch invert telescope 1.12 ft. 
 To find the Wire Constant. First lay off from the center of the instrument, the instrument con- 
 stant, which is the distance from a point in front of the object-glass, equal toils focal length measured from 
 the center of the instrument. Then measure off 100 feet and place the rod truly vertical at this distance. 
 
 Determine the space on the level rod intercepted by the stadia wires. The difference between this read- 
 ing and one foot will be the wire constant, which may be plus or minus, and this constant must be applied t 
 every 100 feet measured, the amount varying with the distance measured. 
 
Tangent Screws. 
 
 These are made of Aluminum bronze, or phosphor bronze, and sometimes of ger- 
 man silver, and are provided with strong spiral springs of german silver, which take up 
 all the dead motion, no matter how long the screw may be in use, or how worn. 
 They are less liable to get out of order, by blows or accidents, than any of the ex- 
 isting tangent screws, and require little or no attention on the part of the engineer. 
 There is no strain on either plate when the instrument is clamped, so that the levels 
 are unaffected. They are set and turned with the greatest ease, following the move- 
 ments of the finger instantaneously with mathematical precision, and do not scratch 
 the plate in revolving instrument. We confidently recommend this form of con- 
 struction to those who have not used our instruments, as the best possible; super- 
 seding the usual methods by means of two opposing screws, or ball tangent screw, 
 greatly in point of convenience and accuracy, and equaling them in point of steadi- 
 ness. By this construction we are also able to fit our upper and lower circle plates 
 so snugly that it is impossible for dust to enter between them. Our leveling instru- 
 ments have the clamp and tangent screws so placed that they can be reached by 
 either hand with the same readiness. 
 
 The Compass. 
 
 The Compass circles are graduated to half degrees in quadrants from to 90. 
 
 The needles are made of superior steel, and tempered all over. A coil of fine wire 
 
 attached to the end pointing South balances the needle for our latitude, which must 
 
 be re-balanced if the instrument is used further north or south of this latitude, and 
 
 must be entirely reversed if used on the southern hemisphere of our earth. At a 
 
 cost of $ 10.00 a variation plate can be placed upon our surveyors' transit to set oft 
 
 the variation of the needle for any particular locality. A stationary pointer just 
 
 above the graduated ring at the North end, and protected by the glass cover of the 
 
 compass, indicates the line joining the vertical plane of the line of collimation of the 
 
 telescope. By means of a milled-headed screw and clamping nut, serving both as a 
 
 handle and a clamp-screw, the graduated ring can be turned past this pointer towards 
 
 East or West as the case may require. 
 
 If it is desired to set off the variation more closely than half degrees, say to minutes, 
 this can be done on the horizontal plate. For more information concerning the oper- 
 ation of the variation plate, read latter part of the article on the compass, page 44. 
 
 Tripod. 
 
 The form we adopt for our instruments is an improvement over what is com- 
 monly termed the " split leg " tripod, used extensively in Europe, which unites the 
 greatest strength and steadiness with the least weight. The tripod-head is cast in a 
 single casting, to avoid all small screws, as well as to attain greater stiffness. For 
 the legs we use the best fine grained white ash, taking particular pains that the 
 grain of the wood runs in. the direction of the leg. They are still further guarded 
 against all possible accidents by wooden tongues inserted at their top. When 
 folded, our tripod is better adapted than the ordinary form, for carrying on the 
 shoulder without irritating the place on which it rests. The good qualities of this 
 over the ordinary round leg tripod provided as that is with unyielding brass cheeks 
 to "tighten" the legs, are so great that there is but one opinion regarding its real 
 advantages, and we gladly bear the greater expense incurred in its manufacture. The 
 cast-steel shoes have projections for the foot, to aid in pressing the legs into the 
 ground. Our levels and transits both fit the same tripod, and are of equal length. 
 
 Shifting: Tripod. 
 
 We have also adapted to all our engineers' transits the shifting tripod or shifting 
 center, by which, after an approximate setting of the tripod, the transit can be 
 immediately brought over a point on the ground. This device we also attach to 
 our instruments with three leveling screws in a roost perfect and simple manner, 
 and without impairing their steadiness and portability. 
 
 Adjustable Plumb-Bob. 
 
 We furnish with all our transits a small brass chain and hook, which are 
 connected to the centers of the instruments. The cord of the plumb-bob can be 
 readily attached or detached from this hook, and by means of a neat, small and 
 simple device, (also furnished with every instrument,) the plumb-bob can be ad- 
 justed over the ground at any height, with hardly any effort on the part of the 
 engineer. 
 
Illumination of Cross-Wires 
 
 For Mining and Tunnel Transits. 
 
 In our instruments this sometimes consists of a hole drilled through the transverse axis 
 of the telescope, and closed at either end with small glass plates, to prevent dust entering 
 the telescope Then in the center of the telescope is placed a small adjustable reflector, 
 by means of which the cross-wires can be very readily illuminated m the mine or tunnel by 
 the reflection of the light of a lamp held in the hand or placed on a small table, which is 
 attached to the standard. This lamp is provided with a ground lens. \\ bile this method 
 is satisfactory, still the small mirror has to be placed at a point where the cone of rays 
 from the object glass is small and consequently it cuts off much of the best part of the 
 litrht not to speak of the weight of the lamp and table at the side of the standard and the 
 heat 'imparted. This method is not thought to be of as good repute as it was formerly. 
 In all cases we would advise the use of our reflector, placed in front of the object glass in 
 a tube like the sun-shade. This arrangement gives perfect satisfaction. This may be used 
 in connection with an ordinary lamp or with the pocket electric lamp. 
 
 Arrangement for Offsetting at Right Angles. 
 
 A perfect line of sight can be had at right angles to the telescope by perforating the 
 telescope axis and covering the ends with glass plates as described in the preceding 
 paragraph. By simply sighting through the axis, offsets may be conveniently estab- 
 lished without disturbing either clamp or telescope when the eye is brought close to 
 the instrument ; its application is, however, limited to even ground. To use it on an 
 uneven ground it is necessary to place the eye at a distance of twelve or fifteen inches 
 from the instrument. The head should then be moved until the eye is in line with the 
 openings of the transverse axis. An offset can then be aligned irrespective of the height 
 of the instrument. 
 
 Quick Leveling Attachment. 
 
 This we can apply to any of our Mining and Mountain Transits and Leveling 
 Instruments. It adds about 1 Ib. to the weight. 
 
 Protection to the Object-Slide, &c. 
 
 A rain and dust guard for the object-slide is now furnished with all of our 
 telescopes, and to insure smooth working of the object slide and telescope tube 
 both are made of a non-friction metal. The graduation of the horizontal circle, 
 the centers and such other important parts that are liable to injury by the action 
 of dust and water in the field-use of an instrument, are entirely protected. 
 
 General Construction. 
 
 In regard to the general construction of pur instruments, the dead weight Ls 
 removed wherever it is shown to be not essential to the stiffness of the instrument ; 
 but we have at the same time strengthened the parts most likely to be injured by 
 jtii accident or fall. Thus the base of the standards, the vernier plate and circle, the 
 parallel plates tor leveling screws, the telescope axis,ihQ flanges of centers, cross-bar 
 of level, etc.^ are made especially rigid and provided with ribs. Instead of finishing 
 the smaller pieces of an instrument separately and then joining them with small 
 screws, or solder, each screw or joint being a weak place in an instrument, we have 
 adopted the opposite principle, (at an increased expense to us,) and aim to unite as 
 many pieces as possible in a single casting, which casting, by means of ribs is made 
 as light as consistent with strength. 
 
 We also call attention to the exceptionally hard bell-metal and phosphor bronze 
 used for our centers and telescope axis, which are long and unyielding, and the 
 remaining parts are of a composition metal, which is itself harder than hammered 
 brass, or red composition, used ordinarily for centers, etc. It is more difficult to 
 work, but we avoid the objectionable softer brass in its use. Experience has 
 proven that soft, or hammered yellow brass is unfit for a good field or astronomical 
 instrument, since it is more liable to fretting and yielding generally, and in the 
 hammered state its unequal expansion and contraction at different temperatures 
 may be so marked as to impair the reliability of the adjustments. 
 
 Aluminum bronze containing 90% copper, is also extensively applied in our instru- 
 ments on account of its great tensile strength. 
 
 Aluminum alloyed with small percentages of silver or copper must be used with 
 caution on account of its softness. (See Aluminum for Instruments of Precision, 
 page 23.) 
 
The Finish. 
 
 It is a well-known fact that the black lacquer finish has one objection, It absorbs 
 the heat readily, and therefore is apt to expand an instrument unequally, and thereby 
 derange its adjustments. We therefore consider it necessary to finish certain parts of 
 an instrument in a bright but not glaring finish including the upper plate and the 
 telescope in the transit ; the cross-bar in the wye level, etc. All other portions may be 
 finished and bronzed before lacquering. This finish gives a very fine appearance to the 
 whole instrument. 
 
 Customers desiring to have their instruments finished entirely in a dark metal color, 
 can do so by notifying us of their wishes. 
 
 Our Wear Resisting Leather Finish. 
 
 The principle is borrowed from astronomical instruments, where it is necessary to 
 cover the surfaces with some non-conducting material in order to avoid disturbances 
 in instrumental adjustments caused by suddenly varying temperatures. 
 
 We have adopted this principle with the view of securing the same results for our 
 transits, wye and dumpy levels. Some of these levels are sensitive to a depression of 
 a single second of arc. 
 
 The exterior surfaces of our instruments so finished have the appearance of being 
 covered with Morocco leather of a smooth and even texture. Its close-grained surface 
 has a most agreeable and soft pliable touch to the hand, and eliminates the disagree- 
 able feeling experienced when metallic surfaces are touched in very cold temperatures 
 or in the tropics. 
 
 Instruments finished in this manner heat up or cool down very gradually, causing a 
 minimum derangement of the adjustments, and being a very dark color this finish 
 unites all the advantages of bright lacquer finishes, with the convenience ot having a 
 dark colored instrument for use in the field, where it does not dazzle the eye of the ob- 
 server in the strongest sunlight. 
 
 Parts so treated can be handled with impunity. This finish is impervious to damp- 
 ness and dryness, or mine and salt water. Dust and dirt can be washed off and candle 
 grease readily removed. Neither will it fade, nor crack, being wholly unlike the anti- 
 quated cloth finish introduced by our senior member in 1871. It is, indeed, entirely 
 in strict keeping with our products. 
 
 It is difficult to determine the wearing qualities of leather and cloth finishes of sci- 
 entific instruments. A good finish must withstand the hard usage of years. The 
 leather finish as applied to our instruments was thoroughly tested for a number of years 
 before being applied to instruments sent out on orders. 
 
 As regards durability, it is quite equal to the bright metal finish, and is superior to 
 bronze or black metal finished surfaces. This, coupled with the fact that it can be 
 restored at any time, same as the cloth finish formerly applied by us (to which latter it 
 is incomparably superior), enables us to unite many parts of an instrument into one 
 piece or casting and thereby secure greater rigidity, lightness and a more elegant ap- 
 pearance than hitherto attained in the instruments of this class as commonly designed 
 and finished. The cloth finish heretofore applied will be used only to a very limited 
 extent. 
 
 Packing. 
 
 In putting our instruments in their cases, none of them separate above the leveling 
 screws. They stand erect, and are ready for use upon unlocking the case. 
 
 The cases are provided with rubber cushions, to check severe jarring arising from 
 transportation over rough roads. 
 
10 
 
 Care of Instruments.* 
 
 Do not allow the legs of your tripod to play loose on the tripod head ; keep nuts 
 and bolts always well tightened up against the wood. Examine the shoes from time 
 to time, and sharpen them if necessary, also screw the shoes tight, if wear and tear 
 loosen them. Be sure your instrument is well secured to its tripod before using it. 
 Bring all four levelling screws to a seat before shouldering instrument. Let the needle 
 down upon its pivot as gently as possible, and allow it to play only when in use ; if too 
 far out from its course, check movements of needle carefully by means of lifter. 
 Never permit playing with the needle, especially not with knives, keys, etc. Be sure 
 to arrest the needle after use, and screw it well up against the glass cover before 
 shouldering the instrument. 
 
 As a rule the compass needle is balanced as nearly as possible for the 
 latitude in which an instrument is to be used. If only a trifle out do not meddle, 
 inasmuch as one can do more harm to the pivot than a small error from non-balancing 
 would amount to, but if the compass needle requires to be rebalanced 
 proceed as follows: 
 
 Remove the compass glass which is held down by a circular ring on top of the 
 glass, which may be removed by inserting the blade of a knife where the two ends of 
 this ring come together and prying gently upward. By means of a piece of beeswax 
 slightly softened, the compass glass may be readily lifted. Then raise the needle up 
 its entire length by means of the lifter and carefully remove it with a pair of tweezers. 
 When the needle is balanced it should be as carefully placed back with the lifter up 
 as before to retain the sharpness of the pivot. If the compass glass needs to be re- 
 moved entirely, unfasten the two screws that screw the stud for the telescope tangent 
 screw to the standards. Don't remove the telescope from its wyes. 
 
 Do not clean the glass cover or the lenses with a silk handkerchief ; breathe over 
 the compass-glass and reading lens if one is used, after cleaning. Examine the but- 
 tons of your coat with regard to iron that may be concealed in them, also beware of 
 nickel-plated watch chains, etc. To clean the object-glass and the lenses use a fine 
 camel-hair brush. If dust or sticky or fatty matter cannot be removed with the 
 brush, take an old clean piece of soft linen, and carefully wipe it off. Do not unscrew 
 the object-glass unnecessarily, this is apt to disturb the adjustment of line of colli- 
 mation. The lens nearest the eye of eye-piece, as well as the front side of the object- 
 glass, need careful brushing withjftne brush from time to time. 
 
 If dust settles on cross-hairs and becomes troublesome, unscrew the eye-piece and 
 object-glass, and gently blow through the telescope tube, cover up both ends and wait 
 a few minutes before inserting the eye-piece and object-glass. Be sure to have the 
 object-glass cell screwed well up against its shoulder, and then examine the adjustment 
 of line of collimation (see adjustment of line of collimation). Do not grease the ob- 
 ject-slide of telescope, or screws that are exposed to dust ; use a stiff tooth-brush to 
 clean slides or threads if dusty. 
 
 To take out the eye-piece, unscrew the screw at the end of the main tube, take 
 hold of the eye-piece and pull it out. 
 
 To focus the cross-hairs, take hold of the eye-piece cap and turn it in a screw-like 
 manner until cross-hairs appear distinct, and as if fastened on the object when the 
 head is being moved. 
 
 Should there bs any fretting in the telescope slide, take it out, and endeavor to 
 smooth the rough part with the back of a pocket knife. 
 
 If the focussing slide seems to work too hard, everything else being right, 4 t 
 is generally caused by the lubricant on the pinion hardening in cold weather, and the 
 same cause may also make the focussing slide work too freely in hot weather by soften- 
 ing, i. e., when not staying in place when in a vertical position. If the slide moves 
 too freely it should be tightened by running out the slide to its full length, then apply- 
 ing a screw-driver to the screw on top of the focussing screw and turning a very small 
 part oi a turn until the required friction is obtained. If the slide works too tightly 
 run in the slide, unscrew the top screw one turn, gently tap it by the screw-driver 
 handle to release it, and then tighten to the required stiffness. 
 
 To prevent the focussing slide from fretting, usually due to the inrush of air car- 
 rying dust and grit when slide is being run out causing momentarily a rarefied space, 
 wrap a piece of chamois skin over the barrel in shape of tubular form and fasten by 
 means of rubber bands or sewing. In an emergency fine watch-oil may be used to 
 grease the slide should it continue to fret, until the instrument can be sent to the 
 maker. In case of rain during non-use, place the telescope vertical, object end up, 
 and no water can enter the telescope. 
 
 Never use emery in any form about any part of a Transit or 
 a t<evel, whether tangent screws, slides or centers. If anything must be used, a very 
 little powdered pumice-stone mixed with fine watch-oil is all that is advisable, and 
 after grinding, then clean thoroughly. The uninitiated are advised to do no grinding 
 
 * For additional suggestions see p. n. 
 
11 
 
 whatever. As a rule more harm than good comes to the instrument. It is only In 
 case of emergency that such heroic treatment should be resorted to. When cleaning 
 the slide and inside of main tube great care must be taken not to break the wires. 
 
 To focus the wires sharply turn the eye-piece slightly to the right or left 
 as the case may be. Remove parallax as explained on page 54. 
 
 To clean the threads of leveling or tangent screws when working hard, use a stifl 
 tooth brush to first clean the threads of all dust, then apply a little oil, and work 
 the screw in and out with alternate brushing to remove dirt and all oil until it 
 moves perfectly free and smooth. 
 
 Screws for the adjustment of cross-hairs should not be strained any more than 
 necessary to insure a linn seat; all straining of such screws beyond this simply 
 impairs the accuracy of instrument and reliability of adjustment. 
 
 When in the field always carry a Gossamer water-proof for the instrument in 
 your pocket, to put over it in case of a shower or dust cloud. On reaching office, 
 after use of instrument, dust it off generally with another fine brush ; examine the 
 centers and all other principal movements to see if they run perfectly free and 
 easy, and oil them if necessary ; also examine the adjustments. This will save 
 expense and many hours of vexation in the field. 
 
 Care of Centers and Graduation. 
 
 As the centers, the telescope axis and the graduations require greater care to 
 preserve their fine qualities, perhaps it is not amiss to say a few words concerning 
 their treatment. 
 
 Upon finding that the centers do not revolve as free as usual after exposure of 
 the instrument in an extremely hot or cold weather, they should be cleaned as soon 
 as time permits, and then proceed as follows : 
 
 Unscrew the milled-head nut at the extreme end of the cylindrical tube containing 
 a spiral spring, which is opposite the upper tangent screw. Do it somewhat cau- 
 tiously, or the spring will fly out. Then unscrew a small cylindrical case, which 
 also has a milled edge, and which is at the bottom of the centers. After unscrewing 
 the nut attached to the inner center, a gentle pressure upwards will lift the vernier plate 
 out from the lower part of the instrument. Take a fine camel hair brush, and with it 
 clean the graduation, the verniers and the inner part of the instrument, but do not 
 rub the graduation, especially not its edge, then take a stick of about the same taper 
 as the inner center, wrap some wash-leather slightly soaked in fine oil around it, and 
 clean the insides of the sockets as carefully as possible; then remove this piece of wash- 
 leather and wrap a fresh piece without oil around the stick and clean dry. Proceed 
 similarly with the centers and their flanges. 
 
 Before applying fresh and pure watch oil, however, care should be taken that 
 not a particle of dust or other foreign matter is left in the sockets, on the centers, 
 or on the graduation. This caution having been taken, the fresh oil should be well 
 distributed on all the bearing parts. It will be well to also examine the arm of the 
 clamp screw of the circle and telescope axis, and if necessary clean by removing 
 washer. After the instrument is thoroughly cleaned and oiled, the nuts and springs 
 screwed back to a firm seat, the instrument must turn perfectly free and yield at 
 the slightest touch of the hand. 
 
 To remove dirt and oxyd that may have accumulated on the surface of a solid 
 silver graduation, apply some fine watch-oil, and allow it to remain for a few hours; 
 take a soft piece of old linen and slightly rub until drv, but without touching the edge 
 of the graduations. If, after cleaning, the solid silver surface should show alter- 
 nately brighter spots, which would interfere somewhat with the accurate reading of 
 the graduation, barely moisten the finger with vaseline and apply the same to the 
 surface; then wipe the finger dry and lightly rub it once or twice around the 
 graduation. Avoid touching the edges as much as possible. Such cleaning, however, 
 must only be resorted to when absolutely necessary, and then only with the greatest 
 care, as it is too apt to reduce the minuteness of the graduation, and spoil its fine 
 appearance. If, after such cleaning, dirt and grease has accumulated on the inner 
 edge of the graduation and verniers, gently wipe clean before restoring the vernier- 
 plate to, its place. Eemember, also, that the centering of the graduations of the 
 circle and verniers is a most delicate adjustment to make. These should never be 
 unscrewed from their flanges by anybody except a maker. 
 
12 
 
 Care of Telescope Lenses. 
 
 As dust and moisture, as well as perspiration from the hands, will settle on the 
 surface of the lenses of a telescope, it becomes necessary that they should be 
 cleaned at times. A neglect to keep the lenses free from any film, scratches, etc., 
 greatly impairs the claar sight through the telescope. To remove the dimness., 
 produced by such a film, proceed thus : Brush each lens carefully with a camel's 
 hair brush, wipe gently with a clean piece of chamois leather moistened with al- 
 cohol, and wipe dry using a clean part of the chamois skin on every portion of the 
 lens, to avoid grinding and scratching. When perfectly transparent brush again 
 to remove any fiber that may adhere to the lens. The tubes in which the lenses fit 
 should be brushed, and if damp should be dried ; this done, restore each lens to 
 its original place as marked. To remove dampness in the main tube of the teles- 
 cope, take out the eye-piece, cover the open end with cloth and leave the instrument 
 in a dry room for some time. 
 
 If an instrument has been exposed to a damp atmosphere, or water has pene- 
 trated the telescope, moisture may settle between the crown and flint glass of 
 which the object-glass is composed. If such is the case expose the instrument to 
 the sun for a few hours, but if in the winter, leave it in a warm room some distance 
 from the stove, the moisture will then generally evaporate. However, if not suc- 
 cessful, unscrew the object-glass from the telescope, and heat it slightly over a 
 stove or open fire. If a film settles between these glasses nothing can be done ex- 
 cept sending the instrument to the maker. The two glasses form one lens only 
 and must not be disturbed, as upon their relation to each other the definition and 
 achromaticity of the telescope depends. Much depends also on the stability, with 
 which these lenses are mounted in their cell, as any looseness between them or the 
 cell will affect the adjustment of line of collimation. Of course, if at any time the 
 object-glass has been unscrewed from the telescope, this latter adjustment must 
 again be verified before the instrument is used. 
 
 Additional Instructions concerning the Care of 
 Telescope Lenses, etc. 
 
 Ever since the introduction of the high power in the telescopes of geodetic in- 
 struments, now used by the best makers, complaints are frequently made of 
 the loss of light in such telescopes and of the hazy appearance of objects 
 viewed through the in, the latter in particular when an instrument has seen service 
 in the field for some time. Now, while the loss of light is wholly due to the greater 
 power as compared with the low powers formerly in vogue, and to the use of erect- 
 ing eye-pieces (see page 31), the "haziness" is produced principally by films 
 of dirt, settled on or between the lenses of a telescope, and becomes even more 
 marked as more lenses are used in a telescope. 
 
 Perhaps it is proper to say here, that when comparisons are made between low 
 and high-powered telescopes of geodetic instruments, other things being equal, the 
 first named, as a rule, will incite favor, because, as in spy-glasses, the image of an 
 object seen through them has a brilliancy never attained by telescopes of higher 
 power. But, whenever the results of stadia work, or fine levelling, as obtained with 
 the more powerful telescope, are compared with those obtained by a lower power, 
 it will be found that, though less brilliant, the defining power of a high-powered 
 telescope is superior to the other within the customary range of distances had in 
 the ordinary engineer's and surveyor's practice, 
 
 On the other hand, owing to the less amount of light with high powers, it is 
 necessary that the fine qualities of the superior lenses required for them should be 
 preserved, and on this account a more frequent inspection and a more careful 
 treatment of them is needed than when lower powers are used, inasmuch as the 
 least impairment of these lenses by films, or dust, etc., will reduce the defining 
 power accordingly. A little extra care, as consequent upon the use of high-powered 
 lenses, is, therefore, imperative, but in so doing one is more than compensated by the 
 satisfaction of having a finer and more penetrating telescope. 
 
 To prevent an untimely settling of a film on the lenses of a telescope, and par- 
 ticularly that apt to form on the inner surfaces of the lenses composing an object- 
 glass that has not been cemented together such film being so fatal in an object- 
 glass because it cannot ordinarily be reached and without disarranging the cross-wire 
 adjustments the treatment of an instrument should be strictly in accordance with 
 the instructions given under " Prevention better than Cure," page 17. Unless these 
 conditions are complied with, the greater efficacy of a telescope composed of supe- 
 rior lenses will be entirely lost. 
 
 Upon finding that, after carefully cleaning the object-glass and the lenses of the 
 eye-piece, the telescope is not as clear as when first received from the maker, then 
 the cause of it is generally a film between the lenses of the object-glass wo take 
 for granted that the lenses are not scratched or otherwise impaired but, as a rule, 
 it takes several years (with carelul use sometimes many years) before such a film 
 
13 
 
 has sufficiently developed to impair the transparency of these lenses. J3ut when- 
 ever it is found that a film has settled between them, then it is best, if the distance 
 is not too great, to send the whole, instrument to its maker, and if this is not feasible, 
 then the telescope, at least, well and soft packed in a box, should be sent. 
 
 Cemented Object-glasses. To prevent the settling of a film between the 
 lenses composing an object-glass, and to avoid disturbing reflections of light from 
 their inner surfaces, such films and reflections imparting to an object viewed 
 through a telescope the hazy appearance noticeable in high-powered telescopes, 
 we now, since 1889, cement these lenses together, so as to form one lens only. The 
 lenses so treated are more efficacious in many respects than when separated by 
 three thin pieces of tin foil, as has been the custom of nearly all instrument 
 makers up to date. 
 
 The cement, however, needs some five or six months to harden, and until it has 
 hardened sufficiently, an exposure to a cold atmosphere causing a greater contrac- 
 tion of the metal cell than the glass, the lenses are very apt to warp, which may 
 lead to a distortion of an object, when viewed through such an objective. 
 
 The proper treatment of an object-glass freshly cemented is to keep the instru- 
 ment, when not in use, in a room having a mean temperature of about 68 F., or 
 slightly above. The same treatment should be followed if it is found that the 
 image formed of an object is slightly distorted ; only in this case the temperature 
 in which it is kept over night should be raised to about 75 or 80 F. This treat- 
 ment applies only to normally mounted objectives. If they are too tightly fitted 
 the lenses cannot be restored to their original efficacy without being attended to by 
 a maker. 
 
 Object-glasses that are cemented are very apt to show some specks, or, with ill 
 usage, cracks in the cement, but, unless the specks are very numerous, so as to 
 cover almost the whole area of the object-glass, the opacity caused by them does 
 not sensibly affect the efficacy of the telescope, and there core need not disturb the 
 mind. Our experience is that the usefulness of an instrument is greatly enhanced 
 when these lenses are cemented together, and that a few specks that may appear 
 after an exposure from a sudden change from hot to a very cold atmosphere, or vice 
 versa, are a lesser evil, as compared with the ill effects produced by a film that in 
 time will settle between these lenses if separated by pieces of tin foil, or even when 
 brought in direct contact with each other, as such a film will have much the same 
 effect as a fog, in preventing vision. 
 
 When, after carefully cleaning the lenses of a telescope, the object-glass of which has 
 its lenses separated by pieces of tin foil, it is found that the image is not as clear as 
 originally, it is a sure sign that there is a film between its lenses, and that it has been 
 exposed to a damp or impure atmosphere, either by injudicious use in the field, or by 
 being left too long a time in the packing box, in which it is protected by cushions of 
 paper or shavings, both of which attract moisture, or by storing it away in its box in 
 such an improper place as a basement or cellar. Such film being noticed, it will then 
 be well to send the object-glass, or much better, the telescope, or, best, if the distance is 
 not too great, the whole instrument, to the maker, in order that the lenses may be 
 cleaned by him, and, if deemed advisable, be cemented. The slight expense incurred 
 of a few dollars will be more than justified by the advantage gained. 
 
 When the object-glass, or telescope is returned after the cleaning or cementing of 
 its lenses, the cross-wire, spirit level, and vertical arc adjustments of the instrument 
 will require a thorough verification before it should be used. In case the whole instru- 
 ment has been sent to the maker, these adjustments are attended to by him. If the ob- 
 ject-glass has been cemented, the telescope should be watched for a year to see that there 
 is no distortion of the image. If there is a distortion, it will indicate that the object- 
 glass has been too tightly fitted, of which fact we should be informed, as also whether 
 after cementing the object-glass the instrument retains its cross-wire adjustment the 
 same as before the cementing took place. If the cross-wire adjustments have to be 
 more frequently made than before the lenses were cemented, it indicates that the object- 
 glass is not tightly fitted to its cell ; and if such is the case it should .be sent to us to be 
 more tightly fitted, after a lapse of about ten or twelve months, when the cement will 
 have sufficiently hardened to allow of a tighter fit of the object-glass in its cell. 
 
 In telescopes of very high power it is of as great importance to keep the lenses of the 
 eye-piece free from grit and films as of the object-glass. Therefore, whenever the tele- 
 scope does not appear to be clear, the lenses of the eye-piece need most careful cleaning 
 (if necessary, every four weeks). The cleaning must be done by first wiping gently 
 with a clean piece of old linen barely moistened with alcohol and then wiping dry, using 
 a clean part of the linen on every surface of the lenses. (Please read the various 
 articles on this point on pages 10, 11 ,and 31, of our handbook and catalogue.) To re- 
 move the eye-piece, unscrew the German-silver screw at the eye-end of the telescope. 
 Of course, after cleaning, every lens must be put back in its tube precisely as marked, 
 and then the outer bearings of the eye-piece in the main tube must be greased with 
 tallow before the German-silver screw is restored to its place. 
 
14 
 
 Additional Suggestions Pertaining to the Care and Pro* 
 tection of Instruments in Field Use. 
 
 In field use, an instrument has to be necessarily exposed to the heat of the sun, 
 and to the action of dust and water; all of these, however, singly or combined, ha/e 
 a tendency to affect its accuracy and endurance. While our instruments in particular 
 have been designed to guard against injuries resulting from exposure of this kind, 
 yet glaring abuses, such as to allow it to stand for hours in the hot sun, etc., without a 
 covering or shelter of some sort, may often lead to a permanent injury to its most vital 
 parts. To preserve the finer qualities of an instrument, viz., the telescope slide, the 
 lenses, the edge of the graduation and verniers, the centers, etc., any undue unequal 
 expansion of the different parts should be prevented. A bag thrown over the instru- 
 ment when not in use, or any shelter that can be had, is to be recommended. Wi ile 
 in use, an umbrella or screen held over it will insure greater permanency of its ad- 
 justments, and the results obtained will be more accurate and uniform than when 
 carelessly exposed. 
 
 To protect an instrument from the effects of salt water, when used near the sea 
 coast, a fine film of watch-oil rubbed over the exposed parts will often prevent 
 the appearance of oxyd. To remove such oxyd-spots as well as possible, apply 
 some watch-oil and allow it to remain for a few hours, then rub dry with a soft piece 
 of linen. To preserve the outer appearance of an instrument, never use anything for 
 dusting except a fine camel's hair brush. To remove water and dust spots, first use 
 the camel's hair brush, and then rub off with fine watch-oil, and wipe dry ; to let the 
 oil remain would tend to accumulate dust on the instrument. 
 
 Lubricating, etc. An instrument used in a tropical or semi-tropical country, 
 or during the warm season in a northern latitude, requires more frequent cleaning, 
 and oiling than in the more temperate climes and seasons ; but so long as an instru. 
 ment works well and the centers revolve freely, it is best not to disturb it. However, 
 If necessary, proceed as described under "Care of Centers, etc." A few additional 
 remarks we give here : Should the centers or the object-slide commence to fret, they 
 should be examined as soon as possible. Once commencing to fret, it grows worse rapidly 
 and oftentimes is then beyond repairing. Never use emery or emery-paper on them, as 
 this will cause everlasting trouble afterwards. After a thorough cleaning of the slide 
 and tube (taking care not to break the cross-wires}, endeavor to smooth carefully 
 the injured parts with the back of a pen-knife, ana barely apply enough tallow to 
 grease the surface of the injured part. If this does not remove the trouble, a little 
 scraping of the roughened parts on the slide, and, if accessible, on the inside of the 
 tube, may become necessary, and apply a mere trifle of finely-powdered pumice 
 stone moistened with oil. Replace the slide and grind a little by moving it in and 
 out; clean thoroughly, and with a piece of charcoal moistened with oil smooth the parts 
 thus ground on the slide. This process of grinding is a most precarious operation, 
 and generally requires the hand of a skillful workman; it should be resorted to only 
 in case of utmost necessity. Whenever permissible, recourse should be had to a 
 maker. These remarks apply equally to the centers. 
 
 The centers of a transit should always be lubricated with fine watch-oil only, and 
 after a careful cleaning; never apply fresh oil before thoroughly wiping off old 
 grit and oil. Rendered marrow is a most excellent lubricant for instruments made o\ 
 brass and the many kindred alloys of copper and tin. In the varying climes of oui 
 northern latitudes this lubricant becomes rigid in cold weather, and an instrument so 
 treated will often become unmanageable in the field. Its application, particularly 
 to the centers of a transit, is therefore restricted to the wanner zones. The use of 
 watch-oil for the finer parts of an instrument, involving freedom of motion, is 
 imperative in our latitudes. 
 
 Many parts of an instrument, especially those whose metal compositions are 
 closely related to each other, may sometimes cause trouble if simply oiled. If they 
 begin to fret and grind, but are otherwise free from grit, etc., the judicious application 
 of a little marrow may prove very beneficial, but it should be cleaned off again as 
 much as possible. The rack and pinion motion and the telescope clamp should 
 always be greased with marrow, but the clamp, tangent and leveling screws, should 
 receive as little of it as possible in the Northern States. 
 
 Vaseline, not having as great a tendency to rigidity under similar circumstances, 
 may prove an excellent substitute for marrow, and may often be applied to level- 
 oenters, where watch-oil would not give the necessary rigidity in the use of the more 
 
15 
 
 ordinary instruments, but it must be renewed quite often. In the finer class of 
 leveling instruments, the centers should be lubricated with oil only, as in transits. 
 
 A great deal of annoyance is caused to the engineer if the eye-piece or the object- 
 slide of the telescope move too freely in their tubes, requiring a re- focussing of the 
 cross-wires and object at every revolution of the telescope in altitude. If the eye- 
 piece can be retained in its socket, with sufficient friction to keep it focussed to the 
 cross-wires, no matter how much it may wabble otherwise, this imperfection (in old 
 instruments) will not lead to any inaccuracy, but if there is not sufficient friction to 
 keep it focussed to the wires, a little rendered tallow or marrow applied to its bearing 
 surfaces in most cases will remedy this evil. Wabbling in the object-slide, however, 
 leading to inaccuracy of collimation, or back-lash in its rack or pinion motion, can be 
 remedied only by a maker; but if the object-slide moves too freely in and out of its 
 tube only, this may be remedied by applying a little tallow to the bearing parts of 
 the rack and pinion, or by tightening the screw in the pinion-head. If not entirely 
 successful, a thin disk made of parchment, or a thin leather-washer, both greased 
 with tallow, and inserted between the flanges of the pinion-head and its socket, 
 will insure the desired result. These latter remarks apply to transit and level 
 telescopes of the customary design. In telescopes, where the object-glass is mounted 
 permanently to the telescope-tube, the eye-piece tube, containing the cross-wires, 
 becomes the slide with which to focus the object. Its motion must be in a line 
 parallel to the optical axis. Any wabbling in this eye-piece slide would lead to in- 
 accuracy in sighting through the telescope, hence it requires the most careful 
 treatment on the part of the engineer. 
 
 Care in the Use of Spirit-Levels. 
 
 Spirit-levels are very susceptible to the least change in temperature, as will be 
 readily seen by the difference in the length of its bubble in varying temperatures. 
 Hence, to guard against inaccuracies from this source, it is necessary that the 
 bubble should lengthen symmetricallv from the center of its graduated scale (sup- 
 posed to be made by the maker), and that both of its ends should be read. Suffi- 
 cient time must also be allowed for the bubble to settle before a reading is made. 
 
 The fluid ordinarily used for levels is pure alcohol, and requires, according to 
 curvature, diameter and length of tube and length of bubble, from twenty sec- 
 onds to one minute to attain its equilibrium. The composition fluid used in our 
 levels for field instruments requires only from five to fifteen seconds of time ; those 
 filled with pure ether, a few seconds only. 
 
 A great source of error in spirit-levels, however, increasing with their greater 
 sensitiveness, is occasioned by an unequal heating of the level-tube, as the bubble 
 will always move towards the warmer spot or end, thereby imparting to the instrument 
 an inaccurate position. This must be attributed to a changed condition in the 
 adhesiveness of the fluid in the level-tube, and not to a change in the form of 
 the tube itself. Therefore, to guard against inaccuracy resulting from sudden 
 changes of temperature, a spirit-level, while in use, should be protected from the 
 sun, and no part of it or its mounting should ever be touched with bare fingers ; 
 neither should it be breathed upon, nor the face of the observer come too close to 
 it. For this reason, in the finer instruments the mountings of our spirit-levels 
 are cloth- finished, and if the levels are detachable they are provided with wooden 
 handles, as the case may require, and glass covers are placed over them whenever 
 deemed necessary. 
 
 If at any time during the progress of field-work a spirit-level has been improperly 
 exposed, it is best to cover it with a cloth for from five to fifteen minutes, before 
 proceeding with further work. 
 
 Mounting Spirit Levels. To prevent any undue strain and change of 
 curvature in spirit levels used in astronomical instruments, they are mounted by us 
 in wyes, as shown in the cuts of these instruments, and are protected from injury, or 
 inaccuracy caused by the breath of the observer and other air currents, by a cover 
 of glass placed over them. Such a mounting, while most suitable for such dslicate 
 levels, would, however, require constant attention and expose a spirit level to break- 
 age in field instruments. To guard against this danger and to lessen the expense 
 wid weight, the spirit levels for field instruments are mounted in a brass tube; but 
 
16 
 
 owing to the difference existing in the expansion and contraction of glass and brass 
 at diiferent temperatures, a spirit level so mounted may sometimes become loose, in- 
 volving inaccuracy and unreliability of adjustment. Upon finding that the adjust- 
 ment of a spirit level in an even temperature is not as stable as desirable, the level 
 fastenings, tube, screws, etc. should be examined, to see if any of them are loose. If 
 the trouble is in the screws, tighten them up; but if the spirit level can be shifted in 
 its tube by a touch of the finger, take it apart ; soften the plaster of paris in water, 
 and remove it with a sharp pointed stick of wood. Cautiously move the spirit level 
 with your finger, at first only a trifle to and fro, increasing the length of stroke little 
 by little, until it can be safely taken out without breaking; clean thoroughly. Cut 
 pieces of white paper, of the width of the radius of the tube, and somewhat shorter 
 than the length of the spirit level, but longer than the opening in the brass tube, and 
 insert these of sufficient quantity at the bottom of the brass tube, to fill up the space 
 intervening between the glass and the brass tube. The uppermost layer of paper 
 should, however, be so wide, as to envelope the spirit level up to the opening in the 
 brass tube. Now insert the spirit level, taking care not to touch the glass ends that 
 are sealed up, and place the division or other marks, indicating wh i re the level has 
 been ground to a true curvature, uppermost in the brass tube. The level must be 
 pushed in with sufficient friction to prevent slipping in the tube, yet not so tight as 
 to cause a crack at a subsequent low temperature, as brass will contract more than 
 glass. No part of the spirit level should touch any part of the metal tube. Now 
 prepare some plaster of paris with water, of the consistency of paste, and pour in at 
 each end enough to fill up the space between the end-pieces and the glass, stirring 
 it sufficiently to make a perfect contact by it and the glass and the brass, but leaving 
 the spirit level ends exposed. Now put the level together, and adjust as described 
 elsewhere. 
 
 There are other causes, such as centers and flanges that have been bent by falls, 
 etc., or that have been worn out unequal expansion or contraction in different tem- 
 peratures of the metals employed in the construction of an instrument, or a non- 
 symmetrical lenghtening or shortening of the air-bubble at different temperatures all 
 of which, singly or combined, tend to impair the adjustment of spirit levels on 
 Instruments. Of these we will not speak here, as it requires a most thorough mecha- 
 nician and instrument-maker to trace the cause to its proper source. 
 
 Being assured that the level is mounted as explained above, our advice is, not to 
 meddle too frequently with the adjustment of a spirit level. Though it may appear 
 to be out one day. it may be in perfect adjustment other days. It is the function of 
 a spirit level to indicate the changes taking place in an instrument, so that the 
 engineer may make proper allowance and apply his corrections, as the character of 
 his work may require. The finer an instrument, the more sensitive the spirit levels 
 must be, in order to admit of corrections to arrive at closer results. As a rule, a 
 spirit level that does not indicate changes taking place in an instrument, is too in- 
 sensitive for the character of the instrument, and in many cases entirely unfit fof 
 reasonably good work. 
 
 Replacing Broken Cross- Wires. 
 
 The cross-lines in our telescopes are bonajtde spider webs (except where plati 
 num wires have been specially ordered). In case they should be broken, they may 
 be restored in the following manner : clean the reticule frame of all foreign matter ; 
 put it on a sheet of white paper with the cuts on its surface uppermost. Prepare a 
 little shellac by dissolving it in the best alcohol and waiting until it is of the con- 
 sistency of oil. From the spider's cocoon, (those from a small black wood-spider 
 preferred), which the engineer has prudently secured at some previous time, select 
 two or three webs, each about two inches long and of the same appearance. Attach 
 each end of these webs to a bit of paper or wood to act as weights, and immerse 
 them in water for five or ten minutes. Remove one web from the water, and very 
 gently pass it between the fore-finger and thumb nails, holding it vertically to re- 
 move any particles of moisture or dirt. Stretch the web carefully over two of the 
 opposite cuts in the reticule frame. Fasten one end by a drop of the shellac, let 
 fall gently from a bit of pointed wood or the blade of a penknife. Wait a moment 
 lor this drop of shellac to harden. See that the web is stretched tight across the 
 
17 
 
 frame, and apply another drop of the shellac to the opposite cut with its enclosed 
 web. Wait several minutes before cutting off the two ends of the web, and then 
 proceed in the same manner with the web which is to be placed at right angles to 
 this one. 
 
 NOTE. The fine spider-threads used were tormerly taken from the cocoons of the small black wood-spider; 
 now, however, we obtain them from the cocoons of a species of spider found in Michigan. These threads ar* 
 almost opaque, and not apt to relax their tightness if properly placed on the diaphragm, and as they retain their 
 elasticity, they are preferable to platinum wires, which have a tendency to break, owing to their great brittle- 
 ness. The best spider-threads are those of which the spider makes its nest. These nests are yellowish-brown 
 balls, which may be found hanging on shrubs, etc. , in the late fall or early winter. The nest should be torn open and 
 the eggs removed ; if this is not done, tne young spiders, when hatched, will eat the threads. The fibers next to the 
 eggs are to be preferred on account of their fineness and darker color. As it is important to get the proper kind 
 of spider-web, we subjoin an extract from a letter addressed to us on the subject by Prof. J. B. Davis, Uni- 
 versity of Michigan, Ann Arbor, Mich., to whom we are indebted for our supply. 
 
 " The species of spider of which I send you cocoons is not difficult to find in Ann Arbor Lat. 42 26' N. 
 as far as my experience goes, and is numerous on Beaver Island, out in Lake Michigan about 46 N. at 
 
 the high 
 
 iite numerously, as I am led to think it is quiet rather than security this spider seeks. The body of the female 
 three-fourths of an inch, I guess, long, and nearly half an inch wide across the abdomen. The male is about 
 the same length, but far slimmer. They are both entirely harmless. I never knew any one to get bitten by 
 either, and many persons in my observation have had them freely crawling over their hands, face and body. 
 They may be certainly gently handled without the least harm. They both (male and female) bear a plain 
 escutcheon design on the back of the abdomen; female much the more beautiful, in browns. Colors all 
 brown and yellowish brown. The cocoon is a snarl of webs, and is attached under ledges of window-sills, cor- 
 nices, projections of gables, and the like partly sheltered places. The color of the threads you have is of a light 
 corn-color, distinctly separating it from the white cotton-like cocoons so common everywhere. The threads are 
 silky, not like cotton. Of late years I keep one or two nice cocoons where they can be reached. You know out 
 can wrap them in a bit of paper and carry them in the, pocket, or any such place, and they are always ready." 
 
 Prevention Better than Cure. 
 
 IT cannot be denied that instruments frequently meet with serious accidents 
 which, with a little care on the part of the operator, could be prevented. It cer- 
 tainly does not betoken proper care to leave it standing unguarded in a street, road, 
 or pasture, or in close vicinity to blasting, or to expose it unnecessarily to the burning 
 rays of the sun, or to dust, dampness, or rain at any time. Such carelessness must 
 inevitably result in deterioration of the accuracy and efficiency, not to speak of the 
 durability, of an instrument. 
 
 It should be borne in mind that there are many parts of an instrument which, if 
 once impaired, cannot be restored to their original efficiency ; and when it is consid- 
 ered that a conscientious maker bestows no little care, time, and expense on his 
 work in order to attain a high degree of perfection, such neglect seems like a 
 wanton waste of human energy and skill. 
 
 Legs of tripods, if fitting too loose or too tight, and dull shoes are frequent 
 sources of falls, and loose shoes tend to make an unsteady instrument. The test 
 of the proper degree of the tightness of the legs is this, that if the leg is raised to a 
 horizontal position and left free, it should gradually sink to the ground. If i+. drops 
 abruptly it is too loose ; if it does not sink it is too tight. 
 
 When taking an instrument from its box, it is not immaterial where and how to 
 take hold of it. To lift it by the telescope, circles, standards, or wyes is improper, 
 and while it may not be attended at once with any senous consequences, yet it may 
 sometimes lead to some permanent injury, and it certainly is always iraught with 
 danger to the permanency of the adjustments. In handling, it is always best to 
 place the hand beneath the leveling base. 
 
 When mounting an instrument on the screw of its tripod, or screwing any of its 
 parts together, it is important to turn the part in the direction of unscrewing until it 
 is perceived by a slight jar that the threads have come to the point where they en- 
 ter; the motion may then be reversed, and the parts screwed together. 
 
 To secure an even wear of tangent and micrometer screws, they should be uae4 
 equally on all portions of their lengths. 
 
18 
 
 Carrying an instrument in cold weather into a warm room, without the pro- 
 tection of its box or bag, will cause a sudden exchange of air within the hollow 
 spaces, and carry with it dust and other substances through the minutest openings. 
 The vapor, also, that will thus condense on the metal surfaces, if it were not pro- 
 tected, will have a tendency to settle a film on exposed graduations, making them 
 indistinct and difficult to read. 
 
 Failure to protect the lenses of the eye-piece and object-glass of a telescope, 
 when not in actual use, from the effects of moisture, dust, etc., by the covers pro- 
 vided for them (eyepiece-lid and cap) will result in a more frequent settling of a 
 thin film, which, like the fatty substance left by the touch of the fingers, greatly 
 impairs the Clearness of vision. That the too frequent cleaning of the lenses must 
 in the course of time be detrimental to their brilliant polish, and lead to a corres- 
 ponding loss of transparency so essential to the proper working of t ^ood telescope, 
 is apparent. Too much care cannot be taken to guard the lenses, and particularly 
 the inner surfaces of the lenses comprising the objective, against any film that may 
 settle on them. The ill effects of such a film are especially noticeable in high-pow- 
 ered telescopes of first-class geodetic and astronomical instruments. In short, it 
 should be remembered that the slightest film, scratch, or dirt will, according to their 
 nature and location, impair the sight through a telescope, and often render it unfit 
 for accurate work. 
 
 The glass covers protecting the compass, arc, and verniers from exposure need 
 very careful brushing and cleaning, the same as the lenses, as any scratch or film 
 will impair their transparency. If at any time the ground-glass shades should lose 
 their pure whiteness, by either dirt or film, and will not act as illuminators of the 
 verniers and graduation, take them out of their frames and simply wash them with 
 soap and water. 
 
 To prevent loss of magnetism in the needle of instruments provided with a com- 
 pass : when storing away, allow the needle to assume magnetic North and South ; 
 then, by means of the lifter, raise it from the center-point against the glass cover. 
 
 If an instrument has met with a fall, bending centers and plates, etc., it should 
 not be revolved any more, in order to preserve the graduations from still further 
 injury, but recourse should be had at once to the nearest competent maker. 
 
 If the box or tripod should have become wet, they should be rubbed dry, and 
 the varnish should be renewed whenever found wanting. 
 
 Loose or detached resting-blocks in the instrument-box, or any looseness of the 
 instrument in them, are very detrimental to the instrument and its adjustments. 
 Cracks in the instrument-box, the absence of rubber cushions under it, worn-out 
 straps and defective buckles, hinges, locks, and hooks, should never be tolerated, 
 as the remedy is so easily applied by any mechanic. Such defects and imperfections 
 are known to lead to injury of the instrument. 
 
 The place where instruments are kept or stored away should be thoroughly dry 
 and free from gases. The placing of fused chloride of calcium, or caustic lirne, in 
 an open vessel in the instrument-box is to be recommended where there is damp- 
 ness ; and if the presence of sulphureted hydrogen is suspected, then, cotton satu- 
 rated with vinegar of lead, placed in the box, will prove a preventive against the 
 tarnishing of solid silver graduations. 
 
 Transportation of Instruments. 
 
 DURING the progress of field work the more ordinary and portable transits and 
 levelling instruments, etc., can generally be carried on their tripods for ease and 
 dispatch. Nothing in the way of precise instructions, however, as to the best me- 
 thod of carrying an instrument : whether on the tripod, in the arm without the 
 tripod placing the hand beneath the leveling base or in the box, can be sug- 
 gested here. The nature of the ground, the surroundings, the size and weight, and 
 the distance to be traveled over, and last but not least the fineness of the instru- 
 ment, will dictate to the engineer the best means of conveying it from point to point 
 in order to protect it from injury, and its adjustments from derangement. 
 
19 
 
 The finer and finest classes of field instruments, such as those provided with 
 micrometer-microscopes, should always be placed in their boxes for safe conveyance 
 no matter how short the distance for fear of improper handling, and because of 
 danger of unequal expansion, temporary as it may be, of such parts as would come 
 in contact with the body or fingers. 
 
 Carrying an instrument on its tripod without slightly; clamping 1 its prin- 
 cipal motions, will wear out the centers. When carrying on its tripod, 
 Plflmn tftlA^PonP J in TRANSIT when placed on a line with its centers; 
 
 e P e } in LEVEL, when hanging down. 
 
 When carrying an instrument in the box it is important that it be placed therein 
 exactly in the position and manner designated by the maker. Therefore, upon re- 
 ceiving a new instrument, the first step should be to study its mode of packing, and 
 if necessary a memorandum should be made for future guidance and pasted in the 
 box. This will save time and vexation, as some of the boxes for field instruments 
 must necessarily be crowded to be light and portable. 
 
 Before placing an instrument with four leveling screws in its box, the foot-plate 
 should be made parallel to the instrument proper, and then brought to a firm 
 bearing by the leveling screws. The instrument must also be well screwed to the 
 slide-board, if one is provided, as is the case in most of our transits. Having put 
 the instrument in the box in such a position, that no part of it will touch the sides, 
 the principal motions are now to be checked by the clamp screws, to prevent mo- 
 tion and striking against the box. Wii,a instruments not standing erect in their 
 boxes, but which are laid on their sides in resting-places, padded with cloth, speci- 
 ally provided for that purpose, their principal motions must not be clamped until 
 the instrument has been secured in a complete state of repose in these receptacles, 
 so as to be entirely free from any strain. Care must be taken, too, that all of the 
 detached parts of an instrument, as well as its accessories, are properly secured 
 to their receptacles before shutting the box. 
 
 When shipping an instrument over a long distance it is commendable to fill the 
 hollow space between it and its box with small soft cushions made of paper, or of 
 excelsior or shavings wrapped in soft paper, taking care not to scratch the metal 
 surfaces, nor to bend exposed parts, nor to press against any adjusting screws. 
 
 For greater safety in transportation by express, the instrument-box itself should 
 always be packed in a pine- wood box one inch larger all around. For the ordinary 
 size of field instrument the packing-case should be provided with a strong rope 
 handle, which, like the strap of the instrument box, should pass over the top of the 
 case and through holes in the sides, the knots being within the case and strongly 
 secured. In cases where the gross weight of the entire package, as prepared for 
 shipment in the above manner, exceeds 40 or 50 Ibs., then two men should handle it, 
 and two strong rope handles, one at each end of the packing-case, should be provi* 
 ded. In order to check jars and vibrations while en route, the loose space between 
 the instrument-box and the packing-case is to be filled with dry and loose shavings. 
 
 The cover bearing the directions should always be screwed on and marked in large 
 black letters. Example: 
 
 THIS SIDE UP. 
 
 HANDLE WITH GREAT 
 
 Scientific Instrument. 
 
 Mr. George Brown, 
 
 36 West Street, 
 
 Value $ Cleveland \ 
 _^ Ohio. 
 
 From JOHN SMITH, Chicago] Illinois. 
 
,20 
 
 The upper halves of the four sides also should have *CARE' and 'KEEP 
 
 DRY ' marked in large letters on them. These precautions are indispensable for 
 safe conveyance while in the hands of inexperienced persons, as without them mes- 
 sengers will often carry them wrong side up. 
 
 The tripod needs packing simply in a close-fitting box. If not placed in a box, 
 it often happens that legs or shoes are broken off while en route, or that the tripod 
 bead becomes bent. 
 
 Many hundreds of instruments, packed as explained above, have been shipped 
 by us, travelling over thousands of miles, over rough roads, on stages and on horse- 
 back; and the instances are so rare where one has become injured (and then only 
 through gross carelessness), that this mode of packing must be regarded as the 
 only proper one for conveying instruments of precision by express or other public 
 carriers. 
 
 Arriving at its destination, an instrument should not remain packed up with 
 cushions, etc., any longer than absolutely necessary. The atmosphere in such 
 boxes naturally must be close and often moist, and consequently has a tendency to 
 produce the ill effects by moisture mentioned in preceding paragraphs. 
 
 Some Remarks Concerning Instrument Adjustments. 
 
 The mechanical and optical condition of instruments used in geodesy, and their 
 adjustments, although satisfactory when they leave the maker's hand, are liable to be- 
 come disturbed by use. It is therefore of vital importance that the person using an in- 
 strument should be perfectly familiar with its manipulations and adjustments. He 
 should be able to test and correct the adjustments himself at any time, in order to save 
 trouble and expense, as well as to possess a thorough knowledge of the condition of the 
 instrument. It is evident that if the character of an instrument is not properly under- 
 stood or if the adjustments are considerably out, the benefit due to superior design and 
 workmanship may be entirely lost. Under these circumstances an instrument may 
 be little better than one of lower grade. 
 
 In the best types of modern instruments the principal parts are so arranged that 
 they can be adjusted by the method of reversion. This method exhibits an existing 
 error to double its actual amount, and renders its correction easy by taking one-half 
 the apparent error. Thus errors of eccentricity and inaccuracy in the graduations are 
 readily eliminated by reading opposite verniers and reversing the vernier plate 180 on 
 the vertical center and taking the mean of the readings , and by repeating the measure- 
 ment of an angle by changing the position of the limb so that the measurement will 
 come on different parts of the graduation. The striding levels and levels mounted on 
 a metal base are readily tested by reversing their position end for end. In the 
 transit plate-levels the adjustment is assured by turning the vernier plate 180. Errors 
 of the line of collimation are detected or eliminated by reversing the telescope over 
 the bearings, or through the standards, as the case may be. In short, an instrument, 
 the important parts of which are not capable of reversing in one way or another, cannot 
 be examined quickly and accurately. 
 
 The adjustments of an instrument, and particularly those of its cross- wires, should 
 be taken up successively in a systematic manner. The proper way is to select a place 
 from which they can be conducted in succession without moving the instrument, as 
 none of the adjustments should be completed independently of the others. This method 
 is followed by the maker, and will save time and vexation. Any auxiliary apparatus 
 that may be available, such as collimators, etc., will be of great service and expedite 
 the work. One of the most important considerations in making adjustments (when 
 the same are greatly disturbed, as when new wires are to be inserted), is to place all 
 the respective parts in an approximate adjustment without introducing any strain 
 except what properly belongs to the action of the adjusting screws themselves. The 
 more natural the method, and the less internal strain introduced in bringing these ad- 
 justable parts into position, the more lasting will be the final adjustments, provided the 
 ustrument is otherwise in good condition. 
 
 It is important that all adjusting screws and nuts should fit truly on the surfaces 
 against which they operate, with only a mere film of tallow between them, so as 
 to insure a true metallic contact, and that they be brought to a firm bearing, yet with 
 out excessive strain. Opposing screws and nuts should always work somewhat freely, 
 so that one can feel when they come to a true bearing. A moderate pressure 
 
21 
 
 applied with an adjusting pin about one and one half inches long, and held between 
 the thumb and forefinger, will then make a perfect contact. For instance, after the 
 opposing capstan-heade I screws of the cross-wire reticule have come to a bearing, it is 
 only necessary to give them each a slight turn, say from 20 to 30 (with the usual pitch 
 of these screws) in order to insure such a tightness that a moderate pressure of the 
 finger upon these screws, or an accidental gliding of the hand over them, cannot change 
 their relative position. On the other hand, if one pair of these opposing screws be 
 fastened tightly during the tentative process of adjustment, there will be, in all likeli- 
 hood, at the end, an excessive strain exerted upon the pair of opposing screws at right 
 angles, which will make itself felt at any change of temperature, or whenever any 
 external pressure may be momentarily applied to them. Jt is but natural that these 
 continual changes in the resultant pressure must affect the adjustments in a like man- 
 ner. To obviate such changes the procedure should be as follows : 
 
 Having placed approximately in position the principal wire of an instrument : viz., 
 in a transit, the vertical wire in a plane perpendicular to the horizontal axis of revolu- 
 tion, in a level, the horizontal wire in a plane perpendicular to the vertical axis 
 of revolution, the other wire should be approximately adjusted for collimation, 
 with the capstan-headed screws only moderately tightened. This accomplished, the 
 capstan -headed screws of each pair in succession should be unscrewed about one- 
 quarter turn, and again screwed tight the same amount. Now if the two pairs of 
 opposing screws have exerted no undue strain upon themselves, the telescope tube, or the 
 wire reticule, the principal wire will still be in the perpendicular plane ; but if the screws 
 have been used too much the wire will have slightly moved out of the perpendicular 
 plane. Therefore all four capstan-headed screws will have to be released again, say 
 about | turn, so that they may be moved simultaneously until the principal wire is 
 again in a plane perpendicular to the axis of revolution, and then each pair in succes- 
 sion must be again tightened an equal amount. The adjustment of the wires lor colli- 
 mation must now be made in turn the less important wire should always be taken 
 up first by slightly releasing the capstan-headed screw away 1 from which the wire 
 must be moved, and tightening the opposite screw the same amount, and repeating 
 this process until the adjustment is gradually perfected. If during this operation either 
 or both of these wires Lave become so much displaced that the capstan-headed screws 
 have to be moved more than a quarter turn, it would be advisable to slightly release all 
 four of them again, in succession, and commence anew. 
 
 It should be said here, that the force applied by the capstan-headed screws 
 cannot break or affect the tightness of the wires in any case, since the reticule, as 
 made by us, although very light in weight, is of a very stiff form. Too great pressure 
 exerted by the capstan-headed screws against the outer tube of the telescope may, 
 however, change die form of the main tube, thereby affecting the true fitting of the 
 object-slide, and creating friction of so serious a nature as to lead to the fretting of the 
 object slide mentioned in other paragraphs. 
 
 In following the above-described course, the cross-wire reticule occupies a position 
 in the telescope free from any excessive side strain ; the result of which is found in the 
 greater permanency of these adjustments ; and although it may require a little more time 
 for an inexperienced person to make the adjustments in this manner, the satisfaction 
 derived from their greater permanency will more than recompense for the extra time 
 spent on them. The adjustments should be made at leisure, and should not be 
 meddled with, unless they appear to be permanently deranged; when, ordinarily, 
 the adjustments will merely require a very slight turn of the capstan-headed screws 
 and opposing nuts in the proper direction. 2 Unequal exposure of the instrument to the 
 sun, or exposure to sudden changes of temperature, may for a time expand some 
 parts more than others, so that the instrument may seem to be slightly out of ad- 
 justment. In such a case it would be better to stop temporarily and cover the 
 instrument with a bag to allow the temperature to become equalized, instead of at- 
 tempting adjustments that would need to be repeated when the instrument is 
 again in a normal condition. The use of metals of different co-efficients of expansion 
 in the construction of corresponding parts of an instrument w?ll naturally lead to a 
 
 1 We refer here exclusively to the more common instruments of American manufacture, where the 
 shoulders of the capstan-headed screws bear against ihe outer tube of the telescope, and where the adjusting 
 threads are contained in the wire reticule. In other designs where, as in most instruments of Cont nenta > 
 Europe, the capstan-headed screws are made to butt ajrainst the wire reticule, the capstan-headed screws 
 towards which the wire mu-t be moved, must first be loosened. In the latter case this action is identical 
 with that of opposing nuts used for the adjustment of most telescope levels on American instruments. 
 2 See page 58. 
 
22 
 
 permanent derangement of adjustment ; such also will be the case when the temperature 
 of an instrument is greatly altered after the adjustments have been completed. A 
 similar result is caused if the bubble of a spirit level should not lengthen symmetrically 
 from the center of its graduated scale in varying temperatures. These imperfections, 
 however, seldom occur in instruments of modern make (or if they occur, they are gener- 
 ally caused because the principal constituents, glass and metal, are substances of 
 widely differing co-efficients of expansion), and are generally so slight in well made 
 instruments, as to be of little practical value, and may be overcome by adjusting the 
 instrument while at a mean temperature of an entire season. 
 
 If an instrument does not remain in adjustment a reasonable length of time, the 
 cause that leads to the trouble, such as a loose object-glass or cell, loose object-slide, 
 worn out screws or bearings, etc., must be found and remedied. If this is beyond the 
 scope of the operator the corrections should be made by an instrument maker. 
 
 Some Facts Worth Knowing. 
 
 The Line of Collimation. 
 
 The expression "Line of Collimation/' usually defined vaguely in treatises ou 
 geodetic instruments, generally means any line of sight in a telescope given by the inter- 
 section of the cross- wires, whether they are in perfect adjustment or not. The term 
 * Line of Collimation," should, however, be confined solely to the line of sight defined 
 by the cross-wires when they are in perfect adjustment, with reference to the optical; 
 axis of the object glass ; and any difference existing between the optical axis of an ob- 
 ject glass and the actual line of sight as delineated by the geometrical axis of the instru- 
 ment is the " Error of Collimation." 
 
 The principal optical axis of an object-glass is the line passing through the optical 
 centers formed by the curvatures and the thickness of the two lenses composing it. 
 Thus it will be seen that it is a well defined axis, giving direction to the light passing 
 through an object glass, and that, when the intersection of the cross-wires is placed in 
 its prolongation at the focus of the object glass, it becomes the axial or fundamental 
 line by and from which all measurements by telescopic sighting are made. It is the line 
 of collimation. 
 
 To make a good instrument, therefore, it is necessary that the outer circumference 
 of the lenses composing an object glass shall be truly concentric with the optical cen- 
 ters. The aim of the maker is to so construct his instruments that this optical axis 
 shall be truly concentric with the geometrical axis of the telescope and that the latter 
 shall also occupy a normal position with regard to the geometrical axis of all other im- 
 portant parts : upon this depends the proper working of an instrument. 
 
 In the larger geodetic and stationary astronomical instruments, the telescopes of 
 which are arranged only for distant sighting, this condition is readily obtained ; but it 
 becomes very difficult of attainment hi the smaller geodetic instruments, since, owing to 
 the varying position of the focussing slide when set for different distances, the optical 
 axis may not always remain truly coincident with the geometrical axis of the telescope. 
 Hence in these instruments, carefully adjusted for distant sights, there is frequently an 
 error of collimation when nearer sights are taken. In the latter case the intersection 
 of the cross-wires remains no longer exactly in the optical axis, its displacement 
 being the cause of the error observed disregarding momentarily the other and more 
 complicated features of different instruments, upon which the line of collimation also 
 depends. 
 
 In the Engineer's transit, however, the line of collimation must also lie exactly 
 at right angles to the axis of revolution of the telescope, so that when this axis- 
 is placed in a horizontal position, the line of collimation shall describe a truly vertical 
 plane, whether the telescope be mounted in the centre of the instrument or outside of 
 the plates, or whether it be focussed for long or short sights. In the more common 
 instruments of this class, where the telescope is situated in the center of the instru- 
 ment, the intersection formed by the line of collimation and the horizontal axis of revo- 
 lution is also required to lie truly in the prolongation of the vertical axis of revolution, 
 so that there be no eccentricity between the vertical axis of revolution and the line of 
 collimation when sights are taken at objects nearer than 200 feet. 
 
 In transits of this latter type, and in which the above conditions are fulfilled, the 
 Bights taken would at once define the true angle, and no reversing of the telescope 
 would be necessary, were it not for other reasons. On account of the necessity for 
 eliminating the eccentricity and error of graduation and verniers, as well as for eliminat- 
 ing errors arising from an inaccurate adjustment of the line of collimation and of th& 
 
23 
 
 adjustment of the telescope in the vertical plane, an instrument should be reversed and 
 an angle should toe repeated. These remarks apply equally to transits made with the 
 telescopes in an eccentric position. If the line of collimation is truly at right angles to 
 the horizontal axis of revolution, the amount of the offset from the line through the 
 center of the instrument to the line of collimation will equal the eccentricity of the latter, 
 and will remain the same whether the sights be long or short. As a rule, however, the 
 small geodetic instruments of the latter class cannot be constructed with the same de- 
 gree of perfection as those with the telescope in the center : and in consequence the 
 engineer using such instruments will have to rely upon methods of observing that will 
 eliminate all instrumental errors. 
 
 In the engineer's wye level the line of collimation must be truly concentric with 
 the object-slide and outer rings ; and it is also necessary that the telescope be well bal- 
 anced from the center of the instrument, in order to project a truly horizontal line. 
 
 Difficult of attainment as the foregoing conditions may seem, it is proper to say 
 that improved tools, and a generally better understanding of the principles governing 
 a telescope and its relation to the instrument, have done so much toward the perfec- 
 tion of geodetic instruments, that while it may not always be possible to make an 
 instrument in which the line of sight for both wires remains true for all distances, that 
 result can generally be secured, for at least the principal wire, without requiring any 
 other but the regular cross-wire adjustment. 
 
 By the foregoing explanation it will be readily understood that it is of great im- 
 portance to have the focussing slide of such a telescope truly fitted, in order that the 
 optical axis of the object-glass may coincide with the geometrical axis of the telescope, 
 whether this slide moves in the main tube and carries the object-glass, as is the custom 
 now in the smaller instruments ; or whether it moves in special rings provided for it in 
 the main tube at the eye-end, where it will contain the eye-piece and the cross-wires, 
 as is the case in all larger instruments. Any lateral motion in the focussing slide that 
 carries the object-glass or the cross-wires, will, therefore, derange the adjustment of the 
 line of collimation. However, it is equally as clear that a wabbling of a focussing slide 
 carrying an eye-piece which serves only the purpose of a compound microscope for 
 close observations of the wires and the image of an object, is of no account save that 
 such lateral motion may be so great that the obliquity which the optical axis of the 
 eye-piece may at times have with respect to the optical axis of the telescope, may cause 
 some parallax, if the wire and image under observation are not sharply focussed to- 
 gether. In concluding, it may not be considered amiss for a full understanding of this 
 subject, to also mention in this connection, that any transparent substance, such as 
 prisms* lenses, or Shade-glasses, introduced between the object sighted at and the 
 object-glass, will deflect the line of sight from its true course, unless such parts can be 
 made optically and mechanically perfect, which is rarely the case without elaborate 
 adjusting apparatus. The introduction of a lens or lenses between the object- 
 glass and wires, or that of a glass micrometer, will also have the tendency to deflect 
 the optical axis and aftect the line of collimation, not to speak of the conse- 
 quent loss of light caused thereby and film forming on the surfaces. For this 
 reason, "Porro's telescope," which requires a lens between the object- 
 glass and the wires, complicates ihe above conditions of a measuring telescope ; and 
 while it may prove of some value in stadia-work to enable to measure from the 
 center of the instrument instead of from a point in front of the object-glass equal to 
 its focal length this feature can never be successfully adapted to the engineer's transit 
 as long as the proper functions of the transit telescope, as explained above, 
 are considered of the greatest importance. The successful performance of 
 an instrument should not be sacrificed for the sake of some doubtful novelty. 
 
 The proper way of attaching prisms and colored glasses necessary to make sun 
 and star observations is to put them upon the eye-piece of a telescope. After the rays 
 from an object have passed through the object-glass and the plane containing the 
 wires, the line of sight as fixed by the object, optical axis, and the wires, cannot be 
 changed by additional refraction. The best way, therefore, is to apply prisms and 
 shade-glasses between the eye and the lens nearest the eye. 
 
 Aluminum for Instruments of Precision. 
 
 In consequence of improvements in the production of pure aluminum and a cor- 
 responding great reduction in its cost, we frequently receive inquiries as to the adapt- 
 ability of this metal for the manufacture of engineers' and surveyors' instruments. 
 
 We may be permitted to say, that while we are among the earliest advocates of 
 aluminum and its alloys for mathematical instruments (see Scientific American, 
 Feb. 1, 1868), we are not so sanguine concerning its adoption for every class of 
 
 * The object prism, so called, attachable to the object end of a mining telescope to aid in steep sighting, 
 from its position between the object glass and the object sighted at, must of necessity be of very limited use- 
 fulness, since the slightest change of the prism or its mounting or a change of the position of the telescope 
 itself or of its object slide will almost certainly deflect the line of sight from its true course and give no satis- 
 factory results. 
 
24 
 
 geodetic instruments, as these inquiries would warrant us to be. There are certain 
 advantages derived from the use of the lighter aluminum instead of copper and its 
 alloys, the metals now employed for field-instruments ; but the disadvantages are 
 that pure aluminum, although very rigid, is nevertheless a very soft metal like tin, 
 and that, when alloyed with 10 per cent, copper, to make it harder, it becomes very 
 brittle, but when alloyed with 20 per cent, or 30 per cent, of copper, it becomes so 
 brittle as to break like glass, therefore, it can be used only with great caution as a 
 material for precise instruments. 
 
 An alloy of 95 parts aluminum and 5 parts of silver by- weight has been found to 
 give good results, being more rigid and harder than the pure metal, and but little 
 heavier, while it is almost as resistent to corrosion, polishes well, and is said to 
 be better for graduation ; but, the fact that it contains silver, will, of necessity, 
 limit its use to the more exceptional class of work. 
 
 Very little is gained in the way of reducing the weight of an instrument by em- 
 ploying aluminum bronze (90 per cent, copper and 10 per cent, aluminum). The 
 parts of instruments made of the latter metal might be easily reduced somewhat 
 in thickness on account of its greater rigidity as compared with copper alloys ; yet 
 to lessen the tendency to vibration, and also in order to withstand the wear and 
 tear of the field use of an instrument, such parts need a little more mass, or dead 
 weight as it may be called. It is then found that the weight of an instrument re- 
 mains materially the same as ever. An exception to the rule may exist in the con- 
 struction of the larger and stationary astronomical instruments, where aluminum 
 bronze may be used to a certain extent to advantage. Its adoption is, however, 
 restricted to non-revolving parts, since, when closely fitted into bearings made of 
 the softer copper and tin alloys, the friction and wear of these parts is so marked 
 that we would never think of substituting it for steel, bell metal or phospho** 
 bronze, or for any work requiring a smooth and accurate motion. 
 
 There can be no doubt that aluminum possesses great utility over brass in the 
 construction of instruments of minor importance. Sextants, reflecting circles, and 
 the more ordinary compasses* can be made of it to some extent, also parts of transits, 
 plane-tables and other instruments, etc. We are using it very extensively, but for 
 reasons already stated above, we are not prepared to advocate its general adoption for 
 instruments of precision. It is only in cases where a judicious use of this metal will 
 be a necessity for the successful construction of an instrument, as for instance in our 
 new style of mining transit, permitting of vertical sights up and down a shaft without 
 the use of an extra side telescope, where certain detachable parts of the instruments 
 are mounted in an excentric position, and unless such parts are made of aluminum 
 they would require a heavy counterpoise. 
 
 It is principally the indiscriminate use of aluminum that we would warn against. To 
 make this fully understood, it will be necessary to explain that all the finer bearings 
 of an instrument made of aluminum, such as centers, object slides, leveling and micro- 
 meter screws, etc., will have to be bushed with a harder and non-friction metal, to guard 
 against friction and wear and to obtain the close fitting of such parts, and permanency 
 of adjustments so necessary in instruments of precision. Now, to make the princi- 
 pal bearings of an instrument of different metals has the tendency to weaken the 
 parts so treated, to make them less secure, and to render the adjustments more 
 liable to derangement on account of unequal contraction and expansion between 
 the two metals. It simply means, then, that the present high state of perfection 
 in geodetic instruments, which retain their adjustment in the varying temperatures 
 and climes of our zone, shall be abandoned, and we go back many years to when 
 the indiscriminate use of widely different metals often made an instrument entirely 
 unreliable, except when used in the temperature in which it was adjusted. 
 
 Modern instrument-making has, however, already achieved great results in re- 
 ducing the weight of field instruments. By improved designs and by the use of 
 harder metals in place of the soft brass, remarkable changes have been brought 
 about in the weight of instruments. They are no longer the heavy and formless 
 structures of soft or hammered brass as of yore, but are of the type and character 
 of a long-span steel bridge, as compared with an old-fashioned wooden structure. 
 Every important member of an instrument is now calculated with regard to its 
 strength, and the materials aie particularly chosen for the part they are 10 perform. 
 Commercial Aluminum, unless obtained from reliable sources, often contains a small amount of iron. 
 
25 
 
 Owing to the many improvements made in the designs, the use of better materials, 
 the application of specially designed tools and machinery, it is no longer necessary to 
 use large and heavy instruments. An instrument of about two-thirds the size and 
 weight of those made formerly will now do the same class of work. It is by these 
 methods that lightness has been gained, and to them we must look for advances in the 
 future. Unless the size of an.instrument is decreased, the resistance of its exposed sur- 
 faces to wind pressure, causing sudden vibrations or tremor in the instrument, will of 
 necessity require a certain amount of weight to secure the needed steadiness, and if this 
 weight is not in the instrument proper, it will have to be in its tripod legs. This is 
 especially true in this era of high telescope powers and sensitive spirit-levels. What is 
 needed is that engineers and surveyors should have more confidence in instruments of 
 smaller size as made by the best makers. 
 
 Wherever less weight is of great importance our patrons should not hesitate to order 
 our smaller Transits Nos. 2, 3, or 4, weighing 10^ and 6 Ibs. respectively, in preference 
 to a larger instrument made of Aluminum and divided to single minutes, but of equal 
 weight. These small instruments are just as durable and capable of doing just as close 
 work as the larger ones. Being mad* of a like metal throughout, whose coefficient of 
 expansion* is lower, they will retain their adjustments better than larger ones made in 
 whole or in part of Aluminum. Suppose an instrument is adjusted in-doors and im- 
 mediately is taken into the cold atmosphere of winter : other things being equal, if the 
 coefficient of expansion of some parts differ the adjustments will very likely be 
 deranged. Besides, the instrument being smaller, the boxes are likewise smaller, thus 
 reducing the weight and making it more portable at the same time. The same, in a 
 measure, can be said of the tripod, although it is against our convictions to use a lighter 
 tripod with a small transit than is used on the larger ones. 
 
 The only exception to the above exists in the Telescope, which, of course, being 
 correspondingly shorter in a small instrument, will have a smaller aperture and less 
 power. However, to secure the same aperture and power for Transits Nos. 2 and 3 
 (No. 4 being inverting), as for our Transit No. 1, with an erecting eyepiece, it is only 
 necessary to order an inverting telescope to attain these conditions. 
 
 In conclusion we wish to say that the future developments in alloying it as a base 
 with other metals, or combination of metals, will be watched by us with due care, and 
 that whenever such developments warrant their adoption for instruments, as already 
 exemplified in many new types of instruments enumerated in our catalog, made in part 
 or almost wholly of such alloys, we are glad to do so. 
 
 * The Ideal metal for a Survey ing Instrument is that -which has a coefficient of expansion equal to that of 
 its glass part* i so as to retain the adjustments in varying temperatures. 
 
 Coefficient of glass per linear foot, for i F 0.000054 inches. 
 
 " steel 0.000076 
 
 " " brass " ""....... 0.000125 
 
 " * aluminum per linear foot, for i F 0.000148 " 
 
 Aluminum is farthest removed from the above requirements, steel or cast iron being nearest, and also 
 fighter and harder than brass ; and non-friction metals would be more generally adopted were it not for the usa 
 of the compass and the liability to rust in the field. 
 
 Repair of Instruments. 
 
 We are often applied to for correcting new and repairing old instruments made by other 
 makers. We will here remark, that as workmanship, material and construction of different 
 makers' instruments vary from one another, it is oftentimes impossible to repair them in an en- 
 tirely satisfactory manner without going into an unwarrantably great expense, or without mak. 
 ing such alterations as would practically make a new one. We will always guarantee in such 
 cases to put the instrument in as good order and adjustment as the character of its construction, 
 workmanship and material, the extent of damage and the general wear will permit, and that all 
 repairs are promptly and conscientiously made. The charges will be according to lime con- 
 sumed, and as low as is consistent with good work. Parties sending instruments should point 
 out in detail whatever parts they wish to have repaired ; but the best course to be pursued is to 
 have the instrument put in thorough order and adjustment, implying, as it does, that the firm 
 should make such warrantable repairs as will make it as serviceable as possible. This course is 
 always more expensive, but the most satisfactory to insure good work, and it is alsothe cheapest in 
 the e'nd. Ourown ins'rumen-s, whenever practicable, should always be sent to us for repairs to 
 insure fullest satisfaction. Much time j nd money H frequently saved by so doin-jr, as we are in a 
 position to duplicite parts from stock on hand, fn sending an instrument to us from a distance it 
 should he carefully placed in its box and then again in a packing box, as explained under " Trans- 
 porta'ion of Instruments," Part I., in order to conform to the rules of most of the large Express 
 Companies, which will admit it to single rates. 
 
26 
 
 Cross-section of spirit levels as used for instruments of precision (see 
 pages 7 and 38), interior surface showing the barrel form with curvature ground to 
 certain value of arc, diameter of arc depending on the degree of sensitiveness required. 
 
 Cross-section of spirit levels as above, but provided with an air-chamber 
 for adjusting length of the bubble for different temperatures as used in the leveling 
 instruments of precision and for astronomical work. 
 
 vision 
 
 TABLE 
 
 * 
 
 I 
 
 e cor re- || 
 tiveness 
 vel. 
 
 9 
 
 1 
 
 1 
 i 
 
 3 ,5 
 
 Showing movement of cross-hairs 
 
 tori 
 
 
 
 Sis 
 
 * 
 
 s 
 a! 
 
 e 
 
 on rod for displacement of bubble 
 
 c 
 e 
 
 1 ' 
 
 |o| 
 
 c 
 
 > 
 h 
 
 il 
 
 for one division of level scale. 
 
 f-8 
 
 ^ 03 
 
 "o fctro 
 
 13 
 
 ' 
 
 00 > 
 
 
 
 i* 
 
 '^. '5 
 
 | 
 
 II 
 
 
 
 AT DISTANCES OF 
 
 o 
 
 || 
 
 O 9 
 
 la 
 
 1 
 
 Feet 
 
 
 
 
 - 
 
 02 
 
 50 100 150 200 300 400 500 1000 
 
 , * -s 
 
 , A N 
 
 Sec. 
 
 Feet 
 
 Inch 
 
 Feet 
 
 Inch 
 
 Feet 
 
 I 
 
 .OOO 
 
 .OOO 
 
 .000 
 
 .OOI 
 
 .OOI 
 
 .002 
 
 .002 
 
 .OO5 
 
 1/20 
 
 8 59 
 
 
 
 5 
 
 .OOI 
 
 .OO2 
 
 .004 
 
 .005 
 
 .007 
 
 .010 
 
 .012 
 
 .024 
 
 I / IO 
 
 344 
 
 
 
 8 
 
 .002 
 
 .004 
 
 .006 
 
 .008 
 
 .012 
 
 .016 
 
 .019 
 
 39 
 
 I/IO 
 
 215 
 
 3/20 
 
 322 
 
 10 
 
 .002 
 
 .005 
 
 .007 
 
 .OIO 
 
 .015 
 
 .019 
 
 .024 
 
 .049 
 
 I/IO 
 
 172 
 
 3/20 
 
 258 ; 
 
 12 
 
 .003 
 
 .006 
 
 .009 
 
 .012 
 
 .017 
 
 .023 
 
 .029 
 
 .058 
 
 I/IO 
 
 H3 
 
 3/20 
 
 216 
 
 15 
 
 .004 
 
 .OO7 
 
 .01 I 
 
 .015 
 
 .022 
 
 .029 
 
 .036 
 
 .072 
 
 I/IO 
 
 "5 
 
 3/20 
 
 172 
 
 20 
 
 .005 
 
 .OIO 
 
 .015 
 
 .019 
 
 .029 
 
 039 
 
 .048 
 
 .097 
 
 I/IO 
 
 86 
 
 3/20 
 
 129 
 
 30 
 
 .007 
 
 .015 
 
 .022 
 
 .029 
 
 .044 
 
 .058 
 
 073 
 
 .145 
 
 I/IO 
 
 57 
 
 3/20 
 
 86 
 
 45 
 
 .01 1 
 
 .022 
 
 033 
 
 .044 
 
 .065 
 
 .087 
 
 .IO9 
 
 .218 
 
 I/ IO 
 
 38 
 
 
 
 60 
 
 .015 
 
 .029 
 
 .044 
 
 .058 
 
 .087 
 
 .116 
 
 .145 
 
 .291 
 
 I/IO 
 
 29 
 
 
 
 70 
 
 .017 
 
 034 
 
 .051 
 
 .068 
 
 .102 
 
 .136 
 
 .170 
 
 339 
 
 I/IO 
 
 25 
 
 
 
 80 
 
 .019 
 
 039 
 
 .058 
 
 .078 
 
 .116 
 
 '55 
 
 .194 
 
 .388 
 
 I/IO 
 
 22 
 
 
 
 90 
 
 .022 
 
 .044 
 
 .066 
 
 .087 
 
 I 3 I 
 
 175 
 
 .218 
 
 43 6 
 
 I / 10 
 
 19 
 
 
 
 7 
 
 .OO2 
 
 .003 
 
 .005 
 
 .007 
 
 .OIO 
 
 .014 
 
 .017 
 
 034 
 
 2mm 
 
 193 
 
 
 
 8 
 
 .OO2 
 
 .OO4 
 
 .006 
 
 .008 
 
 .012 
 
 .016 
 
 .OI9 
 
 039 
 
 2mm 
 
 I6 9 
 
 
 
 20 
 
 .005 
 
 .OIO 
 
 .015 
 
 .019 
 
 .029 
 
 039 
 
 .048 
 
 .097 
 
 2mm 
 
 68 
 
 
 
 2 5 
 
 .006 
 
 .012 
 
 .018 
 
 .024 
 
 .036 
 
 .048 
 
 06 I 
 
 .121 
 
 2mm 
 
 54 
 
 
 
27 
 
 Engineers 9 
 Instruments and Their Adjustments. 
 
 General Remarks. 
 
 THE OPTICAL PART. 
 
 In the construction of telescopes for engineers' instruments, several difficulties 
 present themselves. To be portable, the telescope must be of small aperture, and 
 of short focus. To make it of short focus and yet retain sufficient aperture to give 
 the light necessary with the eye-pieces used, requires especial care on the part of 
 the maker, both in securing the true curves for the crown and flint glass lenses, 
 which make up the achromatic object-glass, and in adapting an eye-piece which 
 will secure a flat field, with the least distortion. 
 
 After careful experiments with the formulas suggested by the distinguished astron- 
 omer, Sir George B. Airy, and the late Mr. Kellner, of Wetzlar, (the two best formulas 
 known), we have adopted the latter. Mr. Kellner's formula employs four lenses, 
 mounted separately, and so arranged as to secure a flat field of the sharpest definition, 
 to the very edge. 
 
 The magnifying power of the telescope depends upon the relation between the 
 focal length of the object-glass and the focal length of the eye-piece, considered as 
 a single lens : Thus 
 
 If F = focal length of the object-glass, 
 
 f = kk ** " eye-piece, 
 
 TGI 
 
 Then -j- = magnifying power of telescope. 
 
 It is readily seen that the magnifying power may be increased or diminished by 
 altering the focal length f , of the eye-piece ; but if the maker increases the power 
 too much, since only a fixed amount of light can enter the object-glass, this fixed 
 amount of light is spread over too much surface in the field of view, and the object 
 seen is therefore too faint. If the maker gets the magnifying power too small, 
 then the engineer has a difficulty in pointing the telescope accurately. Some other 
 points in regard to the magnifying power will be referred to in the description of 
 the transit telescope. We have found about twenty-four diameters to be the most satis- 
 factory power for our Engineers' Transit Telescope ; and for levels the powers in- 
 crease in proportion to the size of the instruments. 
 
 Very much depends upon the optical part of any instrument, and very little has 
 been put into the hands of the practical engineer by which he may rigidly test it. 
 f .C|ie following suggestions may be found convenient. 
 
 The telescope should come sharply into focus, and a very little movement of the 
 focussing screw, either way, should cause the image to blur. When it is sharply 
 focussed, covering any part of the object-glass without altering the focus, should 
 not alter the sharpness of definition but merely cut off light. The pencil of light 
 which enters the object-glass, should come out at the eye end. To ascertain this, 
 gee whether a pointer which you place just in contact with the edge of the object- 
 glass, can be wholly seen in the small disc of light which you will notice at the 
 small opening of the eye end when you draw your head back some inches from the 
 telescope, and point the telescope towards the sky. If the pointer cannot be seen 
 up to the very edge, then the maker has inserted a diaphragm which cuts off light 
 from the object-glass, and, very probably, to conceal the faults in making. In tnifc 
 
28 
 
 case the real aperture of the telescope is found by moving the pointer over the object- 
 glass until its point is just visible, and measuring from the inner edge of the brasi 
 cell holding the object-glass to the pointer. Twice this distance subtracted from 
 the distance between the two edges of the brass cell, will give the real or clear 
 aperture of the telescope. The clear aperture, divided by the diameter of the small 
 circle of light at the eye end, when the telescope is focussed on a distant object, 
 will give the magnifying power of the telescope. Thus the clear aperture of a tele- 
 scope, measured by means of a pair of dividers and a scale, was 1- 35, while the 
 diameter of the circle of light at the eye end, was, 0'- 06. In this case, the magnify- 
 ing power of the telescope was -jr- = 22.5 diameters. 
 
 Another way to determine the magnifying power, is to measure the angular 
 distance between two points with a transit, and then measure the same distance 
 with the telescope of which the power is to be ascertained, placed so that the tran- 
 sit must point into its object-glass and see the same angular distance through the 
 second telescope inverted. Then calling the first angle A, and the angle as seen 
 diminished through the introduction of the second telescope inverted a, we have 
 
 the magnifying power of the second telescope = - an " (? . Thus the angle sub- 
 tended by a window sash, several hundred feet away, was measured by a transit 
 instrument direct, and found to be, 158' 50". When a Y level, previously focussed 
 on a distant object, ws set before the transit, with its object-glass towards th<j 
 transit, the same sash \vas measured and the angle was found to be but 3' 30". In 
 this case, therefore, 
 
 /15S'50"\ 
 
 tan. I ^ 1 tan 059'25" 
 
 the magnifying power of Y level = )r&)"\ tan.V r45" =34 ' diameters -- 
 
 tan. ( 2 ) 
 
 Or, for an approximation, a card cut one inch wide may be set up across a room 
 by the side of a measure graduated to inches. Then, the number of inches on the 
 measure seen by one eye, covered by the image of the white card seen through the) 
 telescope by the other ^ye, will give, roughly, the magnifying power. 
 
 It is dinicult, without months of use, i;o fully test an instrument in all its parts ; 
 but in choosing an instrument the engineer should bear in mind that the making of 
 the transit ana the level are considered to be feats of mechanical skill. It should 
 be remembered that there is no machine so delicate that it can finish the essential 
 parts of an instrument* The last stages in its making must depend upon the personal 
 skill of some mechanic, who has a reputation for that particular work; and we ari 
 sorry to add, that so difficult is it to secure the mechanical skill and patience re- 
 quired in the finishing of the interior pails, the only essential ones, and so easy is 
 it to add the lacquer and polish of the outside, that the market is full of instruments 
 sold at a price enough lower than the best makers can work, to seem to effect a 
 large saving of the first cost; but such a saving is money borrowed at the highest 
 rate of interest, when the cost of annual repairs is considered. It is better at the 
 outset to buy of a maker who is noted for the conscientious accuracy of his work. 
 An imperfect rnck motion ; a screw turned home on the wrong threa'd ; a wabbling 
 of the object-slide or eye-piece; a slight space between the edge of the vernier ana 
 the limb of the c.'rcle ; in fact, any mechanical defect, no matter how slight it may 
 seem, may be taken as a pretty sure indication that the work has been slighted in 
 other parts as well, and should have a strong influence in guiding the selection of 
 an instrument, in the absence of a test by work i the field. 
 
 THE ENGINEER'S TRANSIT. 
 
 In the first part of this catalogue, the peculiarities and improvements in this in- 
 strument have been pointed out. In speaking of the adjustments of these instruments 
 it is well for the engineer to remember that the construction is aimed to be such that 
 \i the telescope and levels are carefully adjusted they may remain so for even a number 
 of years to come, if the instrument suffers no rough usage. 
 
ITrfpodfead 
 
 2 // Bolt 
 
 3 // >/ Mf 
 
 J // Washer 
 
 5 Leg 
 
 6 Footplate 
 
 7 Ba'/ and Socket -Joint 
 
 8 Le/efing Head 
 
 9 a <Scretty 
 
 10 // JcretrCt/ps. 
 /I Shifting P/ate 
 12 Plumb Bob suspending cup 
 IS * H Chain and Hook 
 
 14 Repeating Center 
 
 15 Clamp Collar 
 IGLoverClamp 
 
 51 StdeL/irt Rocker 
 
 52 , tfal 
 
 53 Te/f scope /ix/s 
 
 54 / Barret 
 
 55 E"ye P/ecertountina 
 
 56 Sp/ra/GrwreJcre/r 
 
 57 Terrestrial Eye Piece 
 56 Et/eP/'eceCap 
 
 59 i * Ring 
 
 60 M'/vRet/cu/e 
 6/ a 
 
 64 a ff jcretr 
 
 65 ,i jadd/e 
 
 Thumbscrew 
 Tangent&rev 
 
 17 ,r 
 
 18 
 
 19 * 
 
 20 f ft Piston, Notshom 
 
 21 n t Cap. Not Shown 
 
 22 Inner center 
 
 23 Horizontal Circle 
 
 24 VernierPlare c/amp 
 
 25 
 
 26 Vernier Plate 
 
 27 t a Tangent Bracket 
 
 28 f ,i * iScrfft^ 34 
 
 29 a Spring 
 
 ; 
 
 30 TangentSpringPisto/i 
 
 31 , 
 
 32 Horizontal Vernier 
 
 34 * Shade from? 
 * , Glass 
 
 36 Compass corerG/ass 
 
 37 Meed/e 
 
 38 , P/wr 
 
 39 . Liffer 
 
 40 * i, 
 
 42 
 
 43 
 44 
 
 66 it it 
 
 67 MjectM'de 
 
 68 // Head 
 
 69 /, Glass cell 
 
 70 /, Glass 
 
 '// a aide Dusf Guard 
 
 72 <Si//7<Snade 
 
 73 Telescope Clamp 
 
 <$crev 
 75 * // Washer 
 7$ n 7a/7gent<scn?>r 
 
 77 Vertical C/rc/e 
 
 78 Guard 
 
 \46 * Jldjus table M/e Bearing 
 
 47 a Cap and<Screws 
 
 48 <5ide Level 
 
 19 // // Jdjustingscrev 
 50 t> Fastening jcreir 
 
 Cross Section of the Berger Transit. 
 
 The heavily drawn center line and the two parallel lines drawn at right angles to 
 it in the above cut, indicate conditions required in a perfectly adjusted transit. 
 
30 
 
31 
 
 Description of the Telescope. 
 
 THE object-glass is achromatic, being made of two lenses, one of crown and one 
 of flint glass. Both these lenses are made of the celebrated "Jena" glass (intro- 
 duced about 1885), which has a greater index of refraction and power of dispersion 
 than known before this time. For the most part, that is, whenever the diameter of 
 these lenses is not too large, we since 1889 cement them together so as to 
 make one lens only. In so doing the disturbing reflections from their inner sur- 
 faces, and the settling of a film between them is prevented, besides securing to the 
 telescope an additional amount of light equal to about 8 per cent. The curvatures 
 are computed from special formulae, so that the telescope may have the largest 
 aperture possible with a short focal length. 
 
 The engineer will appreciate the slightest gain in the diameter of the object- 
 glass, since the amount of light received from any object varies as the square of 
 that diameter. Thus an object-glass 1 inches in diameter will admit half as much 
 light again as an object-glass one inch in diameter. 
 
 The eye-piece, or ocular, as it is sometimes called, is the combination of lenses 
 used in the telescope with which the image formed at the focus of the object-glass 
 is viewed. 
 
 The simplest and most commonly used eye-piece in the telescopes of instru- 
 ments of -precision, where spider-threads and micrometers are used in making 
 measurements, is the Eamsden astronomical or positive eye-piece. It consists of 
 two plano-convex lenses, commonly of the same focus, placed apart at a distance of 
 two-thirds the focal length of either, the convex sides facing each other. It has 
 the advantage of being placed behind the focus of the object-glass. It is almost 
 free from spherical aberration, and gives a perfectly flat field of view, so that the 
 spider-threads can be seen distinctly throughout their entire length. Unfortun- 
 ately it is not entirely free from chromatic aberration, that is, not strictly achro- 
 matic, and therefore the Kellnerand Steinheil eye-pieces are frequently preferred, as 
 in them the chromatic aberration is sensibly eliminated, so that a bright object 
 viewed with a normal eye will appear achromatic, a condition as important in the 
 eye-piece as in the object-glass. 
 
 The Kellner eye-piece, also, consists of two lenses. The one nearest the eye, or 
 eye-lens, is a compound lens composed of crown and flint-glass, as in the objective. 
 Both are cemented together so as to make one, to prevent loss of light consequent 
 upon a ray passing from one substance into another. In its common form the eye- 
 lens is plano-convex, with the plane side nearest the eye, while the second or field- 
 lens is double-convex. 
 
 In the Steinheil eye-piece both lenses are compound, as in the eye-lens of the 
 Kellner. The parts of each lens being cemented together, they form two double- 
 convex lenses, and therefore it may be designated as an achromatic double eye-piece. 
 There are some deviations in the construction of the three eye-pieces mentioned 
 above, but mainly as to the proper curvature of the lenses and their proper distances 
 apart, depending as they do on the index of refraction and power of dispersion 
 of the glass used in the construction of the object-glass and eye-piece, but the 
 principle as above explained, by which an achromatic image is obtained, underlies 
 all of them. 
 
 The Ramsden eye-piece is generally preferred on account of its greater simpli- 
 city and its flat field of view, which latter condition is more difficult to be obtained 
 with the Kellner and Steinheil eye-pieces in powerful telescopes of limited length, 
 on account of the somewhat larger field of view possessed by these eye-pieces. 
 Moreover, the compound lenses are liable to be affected after a while by opacities 
 caused by a crystallization, as it were, of the cement uniting the parts composing 
 them. 
 
 Objects seen through the above-mentioned eye-pieces are, however, inverted, 
 and telescopes so constructed are often objected to on this account. It neverthe- 
 less is the most proper telescope to use where fine telescopic measurements must 
 be made, as the image is more brilliant than when the objects are shown upright, 
 and it requires but little practice to get accustomed to its use. The inverting tel- 
 escope has some other advantages that should be mentioned here. The eye-piece 
 being shorter, an object-glass of greater focal length is obtained in the same length 
 of telescope, thereby favoring the conditions imposed to secure the best definition 
 where the telescope must be short and powerful. Any increase in the focal length of 
 an object-glass adds to the magnifying power in the direct way, without entailing 
 the loss of light consequent upon the use of an eye-piece made unduly powerful. 
 On the other hand, an increase in the magnifying power of the eye-piece magnifies 
 the least imperfection that may exist in the object-glass, and makes the cross- 
 wires appear too coarse. 
 
In practice, however, many engineers prefer the erecting or terrestrial telescope. 
 Buch telescopes must be made with an eye-piece consisting of four lenses, as by 
 adding two more lenses, objects are shown right side up, as viewed with the naked 
 eye. In the construction of an erecting eye-piece the chromatic aberration can be 
 corrected by the two additional lenses required to secure an upright image ; but in 
 the case of short and powerful telescopes the difficulties presenting themselves to 
 secure a perfectly flat field of view are very great, and recourse must often be had 
 to a compound lens. In the Kellner terrestrial eye-piece the third lens, reckoning 
 from the eye, is therefore compound, and both parts are cemented together. 
 
 The Huyghenian eye-piece is uued to a very limited extent in the more modern 
 telescopes of instruments of precision. It is most frequently met with in the 
 large telescopes used in physical astronomy, where objects are merely viewed, but 
 no measurements made. The field of view is large, but not quite flat. The amount 
 of light is greater than in the other eye-pieces. The eye-piece consists of two 
 plano-convex lenses with their convex sides facing the object-glass. The main fea- 
 tures are, that in this eye-piece the second lens is placed between the object-glass 
 and its focus, and that it brings the image to a focus at a point half-way between 
 the two lenses of the eye-piece. The focal length of the second lens is three times 
 larger than that of the eye-lens, and they are placed apart at a distance equal to 
 one-half their combined focal length. The image is viewed by the eye-lens. It is 
 called a negative eye-piece, because the image is formed at a point between the 
 
 The magnifying power of a telescope must be proportional to the aperture. If 
 the magnifying power is too high for the aperture, ordinary objects will appear too 
 faint ; and if the magnifying power is too low, the objects will appear so small 
 that the engineer cannot point upon them with sufficient accuracy. 
 
 The magnifying power should be such that the least perceptible motion of the 
 bubble of a level, or change in the reading of the verniers, should cause sufficient 
 movement of the cross-wires over the object in the field of view to be readily notice- 
 able. A higher power than this is worse than useless, since objects are less brilliant. 
 
 A lower power would not develop the full capacities of the instrument. We adapt, 
 therefore, the magnifying power and aperture of our instruments to the sensitiveness 
 of the levels, and the fineness of the graduation. 
 
 In our telescopes the main tube has a much smaller diameter than is usual in pro- 
 portion to the size of aperture. This is accomplished without cutting off any light 
 derived from the object-glass, since the pencil of light within the telescope is contin- 
 ually diminishing in diameter until it comes to a focus at the plane of the spider- 
 lines. The danger of an increase of reflections caused by bringing the interior surface 
 of the telescope-tube nearer to this pencil of rays is neutralized by the introduction of 
 several more diaphragms properly placed, and by the use of a specially dead black coat- 
 ing for the interior. By this method of construction the weight of the telescope is 
 greatly reduced compared with the large apertures used by us, and therefore there is 
 less wear on the horizontal axis of revolution, and less friction of the object-slide. 
 There is, also, on this account, less surface exposed to the wind, and the instrument is 
 consequently more steady. 
 
 Concerning Apertures which are Abnormally Large in 
 Proportion to their Focal Length, for the Telescope 
 of Transits and Levels. 
 
 Having shown in the preceding article the value of the large apertures adopted for 
 the telescopes of the instruments enumerated later in Part II, it seems but natural, in 
 the desire to gain additional light, for those unacquainted with the construction of these 
 telescopes to suggest an increase in the aperture of an object-glass given with a partic- 
 ular length of telescope and size of instrument, that is, to wish to go beyond what in 
 best practice must be considered the limit in diameter of aperture for a given focal 
 length. Good practice allows a ratio of from 1 : 10 to 1 : 12, meaning that an ob- 
 ject-glass one inch in diameter should have a focus of from 10 to 12 inches to insure 
 good light, sharp definition and giving the natural magnifying power of the telescope 
 and not one obtained by applying a too powerful eye-piece and causing undue loss of 
 light. 
 
33 
 
 In order to reduce the size and weight of field instruments and make them more 
 portable and efficient, modern practice has been to reduce this ratio very considerably 
 by adopting as short a focal length as possible, and since the length of telescope is the 
 chief factor in determining the size of an instrument, as will be seen by an inspection 
 of the various instruments .isted later on in this catalogue, the resulting optical and me- 
 dian ical conditions involved are of a most difficult and strained character. Were these in- 
 struments designed merely for viewing objects, asincaseof binoculars, operaglasscs, etc., 
 or for observing stars (which requires no change of focus), so that a short focussing 
 slide would be sufficient, the construction would be a comparatively easy task ; but 
 since these instruments are designed for purposes of engineering and surveying, where 
 angles between sighting poles and height:? of measuring rods must be read at distances 
 which vary from 6 feet to infinity, involving a continual change of the focussing slide, 
 it is of the utmost importance that this slide-tube be of a length which is not only pro- 
 portional to its diameter but also sufficiently long to insure an accurate movement in a 
 straight line coinciding with the optical and the geometrical axes of the telescope, 
 since any deviation in the motion of the slide-tube from a true straight line, whether 
 caused by an insecure short slide or by wabbling or fretting due to too much weight 
 at the object end, will directly affect the position of the line of sight and produce 
 inaccurate results. 
 
 Abnormally Large Object-Glasses. 
 
 The foregoing will show some of the difficulties attending the construction of short 
 telescopes having the largest apertures permissible for surveying instruments. These 
 difficulties are much greater where a short telescope has an abnormally large object- 
 glass. In order to accommodate the cone of light in this case the outer tube has to be 
 greatly enlarged and consequently the focussing slide is then too short and out of pro- 
 portion to its diameter, and the greater weight attached to it such that it cannot be 
 depended upon for precise work. Furthermore such telescopes make an instrument 
 top-heavy, enormously increase the wear on the centers and on the axis of revolution 
 of the telescope, and greatly add to the surface exposed to wind pressure. To over- 
 come some of these defects the focussing slide is often placed at the eye-end of the 
 telescope for certain classes of work where the conditions are more favorable, but this 
 is impossible in the regular engineers' transits, since the eye-piece must always 
 reverse through the standards, and this cannot be done when the slide is drawn out for 
 short distances. 
 
 So far only the mechanical features involved in this subject have been discussed, 
 but it may not be amiss to mention that a telescope with an abnormally large aperture 
 and having an abnormally short focal length very frequently lacks that sharp definition 
 that a smaller object-glass will give. Therefore it is at least questionable whether an 
 abnormally large aperture has sufficient advantage over the usual large aperture to 
 warrant sacrificing the longer object-slide, its greater precision and magnifying power 
 that are obtained when the focal length and the aperture have their normal relation. 
 It should be mentioned also that the special kind of glass required for the largest ob- 
 jectives has not great power to resist the effects produced by moisture in the air, 
 moisture from the fingers, etc., to which it is liable to be exposed in field work. 
 
 Hence it follows that the use of such abnormal apertures should be restricted to 
 instruments for tunnel details or to plane-table alidades'. In all cases where larger 
 apertures are desired, larger instruments with longer telescopes should be chosen, so 
 that the relation between focal length and aperture may be kept the same, and sharp 
 definition, good light and hi.ch power thus insured. For if, in a telescope of short 
 focal length, high power is secured by means of the eye-piece, the difficulty in focussing 
 the wires becomes very marked, and is likely to become a source of annoyance, 
 especially in the case of the very short eye-piece used in inverted telescopes. Further- 
 more such eye-pieces also magnify every imperfection of the object-glass as well as of 
 the cross and stadia wires. This makes it difficult to procure wires of sufficient 
 fineness, and the increased danger of their breaking makes their use almost prohibitive. 
 
34 
 
 The Pancratic, or Changeable Power Eye-piece for the 
 Erecting Telescope 
 
 This feature, long in use in commercial articles such as field-glasses, binoculars, etc., 
 can be applied, in case of surveying instruments, to eye-pieces of erecting telescopes 
 only, and is then desirable only in exceptional cases. Its use in a surveying instru- 
 ment cannot be considered a distinct gain, since it complicates the mechanism of the 
 telescope even in its simplest form by the introduction of a greater number of 
 pieces, besides adding to the weight of the eye-piece. In practical use it requires one 
 more operation than the regular eye-piece, but unless a person is thoroughly familiar 
 with it, not infrequently two more operations are required when focussing on an 
 object. In using it the first operation will be to set the magnifying power, by means of 
 the movable lens, into the first position marked for it ; the second, to sharply focus the 
 wires ; and the third, to bring the object into view. Whenever the power has been 
 changed, by accident or otherwise, the wires will have to be brought again into focus 
 by moving the whole eye-piece in the usual manner. Owing to the greater complexity 
 of this eye-piece some of the lenses are not readily accessible for cleaning in the field or 
 in the office, so that greater care is required to preserve clearness of vision. These 
 lenses are likely therefore to be coated with a film after exposure, thus defeating the 
 very object for which they are designed, viz., to give additional light by the use of a low 
 power. Moreover, when applied to a transit the focal length of the object-glass has to 
 be shortened by about one-half inch, thereby directly lessening the power unless the 
 height of the standards be increased, which of course makes the instrument more top- 
 heavy. 
 
 These are distinct disadvantages in a telescope. The power chosen for the tele- 
 scope of a field instrument is generally the one best fitted for it and therefore should be 
 permanent. To make it changeable in order to reduce this power lessens the degree of 
 accuracy with which a measuring telescope can be pointed at a distant object, and will 
 thwart the intention of the maker, who harmonized the power of the telescope with 
 the sensitiveness of the levels and reading of the graduations. So, to reiterate, it is 
 the discerning power of a telescope, obtained by a normal aperture combined with a 
 sharp definition and high magnification of the object, that will make it possible to 
 quickly and accurately read graduated rods and see staffs at great distances. A low 
 power, therefore, would not reveal the capabilities of the instrument, and on this ac- 
 count the desire is more often expressed to increase the normally large power as 
 explained above in order to read close at long range rather than to have it lessened. 
 
 The aim of the makers is to keep surveying instruments simple in design and free 
 from incumbrances, so that the observer's whole attention may be given to the work 
 before him. While we do not recommend the use of these variable power eye-pieces, 
 when desired they can be applied to the larger size transits and levels when made to 
 order. 
 
 The Graduations. 
 
 Engineers' transits have various graduations on their circles, according to the 
 requirements of the different branches of civil engineering. These various gradua- 
 tions are read by opposite verniers, which may be either single or double. Ameri- 
 can instruments have usually double opposite verniers, commonly reading the 
 circle to single minutes or to thirty seconds. For a higher grade of work, required 
 in the larger cities and on extended land surveys, they should, however* read to 
 twenty or ten seconds according to size of circle. 
 
 Transits intended for triangulation should have only single opposite verniers and 
 one row of figures clockwise from to 360. 
 
 All instruments desired with graduations differing from those specified in this cat- 
 alogue under each style and size, will be made to order only. 
 
 The customary graduations of C. L. Berger & Sons' instruments are as follows : 
 
 The circle divided to half degrees, the verniers reading to single minutes, see Fig. 1. 
 t i < u < twenty minutes, " " " " thirty seconds, " Fig. 2. 
 
 << .. fifteen minutes, " " " " twenty seconds, " Fig. 3. 
 
 " " twenty minutes, " " " " twenty seconds, " Figs. 4, 5 and 6 
 
 i K " ten minutes, " " " " ten seconds, " Fig. 7. 
 
35 
 
 To express the relation between the vernier and circle divisions, let d=the rn tu 
 of one division of the circle; d'=the value of one division of the vernier; d-d'= 
 the least count of the vernier, or, in other words, the smallest reading of the circle. 
 
 n= the number of spaces of the vernier which correspond to (n 1) spaces of 
 the circle. 
 
 We then have the three formulas ; 
 
 (1.) 
 (20 
 (3.) 
 
 d d'= 
 
 Thug, for example, suppose the circle was divided to 15', and it was desired to 
 read to 20". Here,d=15' 
 
 d d', or, the least count: 
 Then, by formula (1) 
 
 n 
 
 =45 
 
 Therefore, 45 spaces of the vernier must correspond to 44 or(n-l) spaces of the 
 circle. 
 
 Suppose again the arc to be divided to 2CK, and to be read to 30". In this case 
 we have 
 
 Therefore, 40 spaces of the vernier must correspond to 39, or (n 1) spaces of 
 the circle. These are the graduations which Messrs. C. L. Berger & Sons usually 
 adopt for engineers' transits. 
 
 2.2.0 
 
 The cut fihows a portion of the circle and vernier, to illustrate the method of 
 reading to thirty seconds. 
 
 The lines marked 130, 140, and 150 denote 10 each. The shorter lines half way 
 between them denote 135 and 145. The next shorter lines denote whole degrees, 
 while the shortest lines are one-third of a degree, or 20 / apart. 
 
 The vernier comprises the upper series of lines. Of this series only that half 
 lying to the right of the vertical arrow, or zero, and having the figures 10 and 20 
 inclined in the same direction as the 130, 140, and 150 of the arc, is to be used in 
 connection with these figures. The vernier is double, one half to be used with 
 one set of graduations of the arc, the other half to be used when angles are laid off 
 in the opposite direction, and then the lower set of figured, 210, 220, and 230 are used. 
 
 It is to be especially remembered that the figures on the vernier are inclined in 
 the same direction as the figures on the arc to which they belong. 
 
 To read the vernier, first note the whole degrees, and 20 7 spaces lying between 
 the last 10 degree division and the zero division of the vernier. 
 
 Thus in the cut, using the upper line of figures, the zero of the vernier has passed 
 
the 130 division, and moved on until it is between the 20" and 40' space beyond the 
 138 mark. The first part of our reading will therefore be 138 20'. 
 
 Second, look along the vernier, beginning from the zero point, and in the direc- 
 tion in which the graduation of the arc runs, until one line of tiie vernier is found 
 which seems to be a prolongation of an opposite line on the arc. 
 
 Consider each of the vernier spaces between the vernier zero and such a line, 
 as equal to 30" of arc. 
 
 Add the number of minutes and seconds thus obtained to the first reading. The 
 result will be the reading of the circle. 
 
 Thus we notice that the vernier zero is a trifle over half-way of the distance 
 between the 20 7 and 40' marks of the arc. 
 
 And looking along the vernier to the right, we notice that the lines of the ver- 
 nier gradually approach the lines on the arc until the twentieth line of the vernier 
 is precisely opposite a line on the arc. Of course, since each vernier space denotes 
 30", the alternate ones made a little longer in the cut will denote single minutes, 
 and on the vernier therefore the twentieth line would correspond to 10' 00", and 
 since our first reading was between 20' and 40', this vernier reading is to be added 
 to that first reading. 
 
 Thus, 138 20' 
 
 10' 00" 
 
 138 30' 00" will be the reading of the vernier, 
 
 using the upper graduation. 
 
 In the same manner we proceed to the left in reading the lower graduation, in 
 which the figures are inclined to the left. Thus in the cut, we should find the zero 
 point of the vernier is beyond the 221 20' mark, and the line of the vernier, which 
 it seemingly a prolongation of a line of the arc, corresponds to W 00". Then we 
 hare 221 20' 
 
 10' 00" 
 
 221 30" 00" for the reading of the vernier, using 
 the lower graduation. 
 
 Practically, in reading the vernier, the engineer decides which line is in coinci- 
 dence by the position of the lines on both sides. 
 
 He first notices, roughly, what fractional part of a space on the limb lies between 
 the vernier zero and the last graduation mark it has passed. This enables him to 
 look immediately to that part of the vernier in which the coincidence occurs. 
 
 Thus in the figure the vernier zero is about half way between 221 20' and 221 40% 
 the engineer therefore immediately looks about half way along the vernier and 
 finds the 10' 00" division to be the one sought. 
 
 When the graduation is to thirty seconds, the engineer will find that if he only 
 chooses, lie can work to minutes with this graduation quite as rapidly as with a 
 transit graduated to minutes, by simply disregarding the shortest lines of the vernier. 
 
 The second vernier, which is distant 180, or exactly opposite the one read first, 
 may also be read. Not so much to eliminate any eccentricity of the circle and ver- 
 niers as to afford a valuable check upon the angle measured. 
 
 Greater accuracy in the measurement of any angle may be obtained by the 
 principle of repetition. In this case, before and after an angle has been repeated a 
 number of times, all four of the verniers should be read, and if, for example, the 
 graduations proceed from right to left, the left hand side of each double vernier 
 should be read as usual ; but hi the right hand side the line now marked 20 on the 
 vernier should be considered 0, and the arrow on the vernier 20. Then, with this 
 convention, only the minutes and seconds of the second vernier should be used. 
 
 But it should be here remarked that the repetition of angles is not now hold in 
 such repute by our best engineers, as it was before the present perfection of the art 
 of graduating and centering the circles and verniers of engineering instruments. 
 
 The engineer who has not used them will find the ground-glass shades a great 
 convenience in reading the vernier. They are so placed as not to be readily broken, 
 and they shed a clear, white light upon the graduations. 
 
 Graduations on solid silver are much to be preferred to graduation* on any 
 known brass alloy. The surface of the silver can be worked very plane, since it is 
 of uniform texture. The graduations can be cut with the utmost uniformity In 
 width of line and spacing. 
 
 The graduations on a BERGER Transit are not mere scratches on German 
 Silver ; they are extremely accurate, have great depth of line, and are clearly 
 cut and on 925/lOOOths Sterling Silver, being easily read, even in a faint light ; 
 the lines are of just the proper length so as not to be fatiguing to the eye. 
 
 The figuring of the circles and verniers is unusually distinct. 
 
The Customary Graduations of Circles and Verniers 
 for C. L. Berger & Sons' Instruments. 
 
 Figures 1, 2, 3 and 4 illustrate graduations in which the horizontal circles have two 
 rows of figures, from to 830, in opposite directions. The figures in the main row 
 nearer the vernier increase clockwise, and in the other row increase in the opposite 
 direction, so that angles may be read rapidly in either direction. Other figuring, such 
 as to 90 to 0, to 180 to 0, will be made when specially ordered. 
 
 The vertical semicircle is figured from to 90 in either direction for reading angles 
 of elevation or depression, and the full vertical circle from to 90 to 0. For astro- 
 nomical work the vertical circle will be figured clockwise from to 360 when spe- 
 cially ordered. 
 
 Whenever a change is desired from the customary figuring, as given below, a diagram 
 should be sent with the order. 
 
 The size of circle appropriate with the various graduations and verniers will be found 
 in the description and extras of instruments in the catalogue and are the ones recom- 
 mended. A larger size of circle than the one enumerated with the instrument would 
 often prove of no value, while a smaller size may prove fatiguing to the eye to read. 
 
 The cuts below represent a graduation on a circle 13 inches in diameter. 
 
 Graduation Reading: to Minutes. 
 
 50 
 
 w 
 
 360 
 
 Fig. I. 
 
 Fig. 1. Circle divided into 30' spaces. 
 
 Double Opposite Verniers to Horizontal and Vertical Circles, also for arcs (29 spaces 
 into 30) reading to single minutes. 
 
 Note.- 
 
 ing folding 
 
 its zero point in the center and extends 15' each way. In reading this vernier, proceed to the right or 
 left on the upper row of figures in the direction of the graduation used, and if the coincident line 
 is not found before reaching the 15' line, continue on the lower fine of figures on the other half of 
 the vernier, so that the whole graduation from (X to 3<y lies in the same direction. 
 
 . Sometimes when for want of space in some particular type of instrument a single read- 
 ig vernier must be applied to a circle figured in opposite directions the single vernier has 
 its zero point in the center and extends 15' each way. In reading this vernier, proceed to the right or 
 
 Graduation Reading to 3O". 
 
 280 
 
 Fig.2. 
 
 Fig. 2. Circle divided into 20' spaces. 
 
 Double Opposite Verniers to Horizontal Circle (39 spaces into 40) reading to 30". 
 
38 
 
 Graduation Reading to 2O". 
 
 A 
 
 15 
 
 J50 
 
 J60 
 
 Fig. 3. 
 
 Usual Style of 20" Verniers for the Engineer's Transit. 
 
 Fig. 3. Circle divided into 15' spaces. 
 
 Double Opposite Verniers to Horizontal Circle (44 spaces into 46) reading to 20". 
 
 Note. In figure 3 the lines on both the circle and the verniers are considerably closer than in 
 those of figure 2. For this reason it will be seen that this graduation is more fatiguing to the eye to 
 read. However this form is the only feasible one for the vernier opening when two rows of figures 
 with zero in center of vernier are required, as in general engineering work where angles are to be 
 read rapidly to right and left. For the best vernier for triangulation transits see figures 4 and 5. 
 
 Graduation Beading to 2O". 
 
 .4. 
 
 For the Engineer's Transit intended for Triangulation. Made to order only. 
 
 Fig. 4. Circle divided into 20' spaces. 
 
 Single Opposite Verniers reading to 20" (59 spaces into 60); two zero points to Ver- 
 niers ; two rows of figures. 
 
 Note. This vernier has wider spacing on the circle and on this account is more easily read to 
 20", but has the disadvantage that when an engineer wants double opposite verniers, as shown in the 
 verniers Figs. 1, 2, and 3, the opening of the vernier plate would have to be twice as long and there- 
 fore too large for the superstructure of the instrument. It is desirable in such cases where an en- 
 gineer wants a 20" graduation on above limb with two rows of figures to provide verniers with 
 two zeros, one at each end, as shown above, necessitating the inconvenience of first shifting the ver- 
 nier plate from one zero to the other before angles can be read in the opposite direction. 
 
 This difficulty may be avoided, however, by using the 10' mark on the vernier as the zero point 
 and reading angles in either direction as explained under figure 6. 
 
 Graduation Heading to 2O". 
 
 A 
 
 Usual Style Vernier for Transits intended for Triangulation. Made to order only. 
 
 Fig. 5. Circle divided into 20' spaces. 
 
 Single Opposite Verniers reading to 20" (59 spaces into 60). One row of figures. 
 
Graduation Reading to 2O". 
 
 A 
 
 Fig. 6. 
 
 Folding Vernier. Made to order only. 
 
 Fig. O. Circle divided into 20' spaces same as Nos. 4 and 5. 
 
 Single Opposite Verniers having one zero point in center with two rows of figures. 
 
 Note. With this style of single vernier angles may be read to left or right. If angles are being 
 read clockwise start with the zero point under A and continue to the left until the 10' mark is 
 reached, then if no coincidence is found, continue by taking the 1(X mark at the opposite end of the 
 vernier (right end) and reading toward the 2(X mark. In reading angles in the opposite direction use 
 the figures which slope toward the right. 
 
 Graduation Reading* to 1C" (on a 7 or 8-inch Circle). 
 
 Fig. 7. 
 
 Usual Style of Verniers for Triangulation. 
 
 Fig. 7. Circle divided into 10' spaces. 
 Single Opposite Verniers reading to 10" (59 spaces into 60). 
 
 Whenever desired double opposite verniers can be furnished, with two rows of 
 figures on limb from to 360 in opposite directions. 
 
 Note. In cases where less weight and greater compactness and portability of instrument are 
 desirable, as in instruments often furnished to the Government for use in mountains and in the 
 tropics, a 10" graduation can be placed upon a 6# inch circle. The spacing however is very close, 
 and while this size of circle will give almost equally as accurate results, its reading must neces- 
 sarily prove more fatiguing to the eye. 
 
 Graduation Reading to 5" on 8-inch Circle. 
 
 Sometimes it is requested to graduate an 8-inch circle to read to 6" direct, when the 
 circle will be divided into 5' spaces and the vernier 59 spaces divided into 60 parts. As a 
 rule this r^aduation is not desirable for vernier instruments on account of the close 
 spacing on circle and verniers which of necessity must prove inconvenient in usual en- 
 gineering practice because of its greater liability to error in reading. 
 
Decimal Vernier Graduation. 
 
 For railroad work it is sometimes requested to graduate vernier A to read to 
 minutes or 30", as usual, and vernier B to read to T pth of a degree. 
 
 If the circle is to read to minutes, vernier A will be as shown in figure 1. A 
 decimal vernier for this graduation requires 49 spaces of the circle to be divided into 
 50 parts on the vernier, making a very long vernier, so that there is only room for a 
 single vernier in the opening of the vernier plate. This vernier would either have two 
 zero points as in figure 4, or would have the zero at the center, as shown in figure 6. 
 
 If one vernier is to read to 30" and the other to T ^th of a degree, the circle would 
 be divided into 15' spaces, and the A vernier would be as shown in figure 9. The 
 decimal vernier for this graduation requires 24 spaces of the circle to be divided into 25 
 parts on the vernier as shown in figure 8. 
 
 The disadvantages of such graduations are, first, that the spacing of the circle is too 
 doss for rapid reading, and second, that mistakes are liable to be made in reading the 
 verniers by confusing the 30" reading of vernier A with the T ^th of a degree of 
 vernier B. Another disadvantage is that when it is desired to read both verniers, 
 A and B, as in repeating angles, this cannot be conveniently done with either of the 
 above arrangements. For these reasons the two verniers A and B, should have the 
 same graduation. 
 
 There are occasionally inquiries for transits provided with decimal vernier gradua- 
 tion. These can be furnished when desired, but must be specially made to order. On 
 account of the great length of the double vernier, single opposite verniers of the fold- 
 ing pattern (fig. 6) are the only feasible ones. Although objections are often raised 
 against them, still many engineers like folding verniers after becoming accustomed to 
 them. 
 
 Decimal Vernier Graduation. 
 
 10 
 
 8. 
 
 r. 8. Circle divided into 15' spaces. 
 Double vernier (24 spaces into 25) reading to hundredths of a degree. 
 
 Graduation Heading to 3D". 
 
 On same limb with B vernier to read to lOOths of a degree as in Fig. 8, and A ver- 
 nier reading to 30". 
 
 360 
 
 Fig. 9. 
 
 . 9. Circle divided into 15' spaces. 
 
 Double vernier A (29 spaces into 30) reading to 30". 
 of a degree. 
 
 This vernier is not commonly used, but has the advantage that the double vernier 
 occupies only a short space. 
 
 B vernier reading to lOOtns 
 
41 
 
 Graduation Reading to Hundredths of a Degree. 
 
 A 
 
 \o 
 
 Fig. 1O. Circle divided into 30' spaces. 
 
 Single vernier (49 spaces into 50) reading to hundredths of a degree. 
 
 Two Zero Points to Verniers ; Two Rows of Figures. 
 
 Inclination and Color of Figures for Graduations. 
 
 All of the double verniers shown above require the limb to be provided with two 
 sets of figures in black, as indicated in the diagrams and further illustrated in the 
 diagrams of the various limbs on the following page. To prevent mistakes, the 
 figures of each row are inclined in the direction in which the ver- 
 niers must be read. It will be noticed that the figures above are inclined only 
 enough to easily distinguish each row from the other. If the figures are inclined at too 
 great an angle their distinctness would be impaired and considerable difficulty would 
 be experienced in reading them correctly, and would be apt to lead to gross errors. 
 The shape of the above figuresis very plain, so as to standout clearly. If desired, the 
 figures of the contra-clockwise row, with the figures of its corresponding verniers, and 
 those of the vertical circle, can be furnished, without extra cost, in a red color, to further 
 distinguish them from the clockwise graduations. There is, however, no advantage 
 in the red over the black figures, since the latter stand out very plainly on a silver sur- 
 face, and are very distinct, even after the silver has somewhat tarnished, is soiled, or 
 when the graduations must be read in a faint or artin'cal light, where the red figures 
 will not show a marked contrast to the black. 
 
 If red figures are desired, the code word "Reddish" must be used, and such 
 Transits will have to be especially made, not being kept in stock. 
 
42 
 
 Figuring of Graduations. 
 
 HORIZONTAL CIRCLE 
 
 HORIZONTAL CIRCLE 
 
 DIAGRAM Q 
 
 CODE: SAPPHIRE 
 
 HORIZONTALClRCLE 
 
 HORIZONTAL CIRCLE 
 
 Bin- WITH ZtROSjSOViBWT 
 
 CO**SSVAMAT)OMraM6 WITHTVP ROWS orncuRCS: 
 
 COMPASS RING neuRto 
 
 AS5UPfUtDVTHTRANSrr3 
 
 WITH CARDINAL POINTS ENGRAVED ON 
 
 ^ \ VLRTICALClRCLtruOlNQUAORANT5 
 
43 
 
 The Centers. 
 
 Quite as important as the graduation, is the exact fitting of what the makers 
 call the centers of the instrument; i.e., the two vertical metafaxis, about which thl 
 circle and the vernier plate turn. 
 
 Both axes must be exactly concentric with the center of the graduated oirclp 
 and the center of the horizontal axis of the telescope in any position of the instru- 
 ment. The most sensitive level about the instrument should not show anv disnlace- 
 ment when the circle-plate is held, and the lower plate moved by the hand 
 
 In the construction of the inner center, the hardest bell-metal should be used 
 and for the outer center a red composition metal of the best quality. To insure a 
 true concentricity of the axis, and consequently of the limb and vernier it is 
 necessary that they should each be turned in a dead center lathe, each about its 
 own axis. In fitting the centers, they should turn without the slightest play, and 
 yet with very little friction. 
 
 We take the precaution of casting the outer center, circle and vernier plate in the 
 same mould, to avoid any difference in the composition of the metal. 
 
 The upper plate should not be hammered, since this would also effect an unequal 
 expansion of the metals in extreme temperatures, causing the vernier to read too 
 long or too short. 
 
 After the plates are put together, the vernier and limb should revolve in the 
 same plane, to avoid parallax. The space between the limb and vernier should 
 have the appearance of a uniform, fine, black line. 
 
 The Compass. 
 
 In running old lines, and as a check in running new ones, the compass is frequent- 
 ly a very important part of the transit. Its needle should be fcnm|tc.rr.<| throughout, 
 and of hard steel, to retain its magnetism. It should be thin, and yt at tho game 
 time have enough surface to be strongly magnetic. It should be swung upon a 
 iewelled center, and so nicely fitted that when at rest, with the instrument levelled, 
 the two extreme points should just clear the graduation of the compass box, and 
 read precisely 180 different in any part of the graduated arc. The pivot on which 
 it swings should be conical, and hardened so that it may swing upon a sharp point, 
 without having this point weak. 
 
 The needle should also be so sensitive, that when drawn from its pointing by 
 the outside attraction of a piece of iron held in the hand a foot or so away, it will 
 settle to the same reading several times in succession. 
 
 This sensitiveness depends upon the form and sharpness of the pivot, the strength 
 of its magnetism, and its bearing on the jewelled center. 
 
 If it should be found that a needle has lost its sensitiveness, it is probably not 
 BO much owing to its loss of magnetism, as to a dulling of the pivot. Since this 
 may happen when the engineer is without access to the maker, and an instrument 
 otherwise be in good condition, it should be remarked that the pivot can be sharp- 
 ened after removing the needle, by taking a fine oil-stone, and while turning the 
 instrument with one hand, grinding the pivot, with the oil-stone in the other ; being 
 careful to incline the grinding surface about 25 to the pivot. The pivot is origi- 
 nally turned and sharpened in a lathe, and in grinding by hand, great care should 
 be taken to preserve its conical form. 
 
 The two extreme points which lie next the graduation, together with the point 
 of suspension, should lie in one straight line. 
 
 The center of gravity of the needle should be as far below this line as possible. 
 
 The quivering of a needle so constructed is not annoying, since the center of its 
 quivering motion is in the line through its two extreme points, which are, therefore, 
 stationary. 
 
 To determine whether the transit itself has any iron in it to disturb the needle, 
 it is a good plan, after setting the instrument so that both compass-needle and 
 vernier reads 0, to go round the circie, setting the vernier ten degrees ahead each 
 time, and noting whether the compass-needle also describes an arc of precisely ten 
 degrees. If it does not. there is some local attraction. 
 
 The graduations on the compass box should begin at the North point, and run 
 90 in both directions ; then decrease to again at the South point. In mine 
 transits a second continuous row from to 360 starting at North is placed on 
 the compass ring. Other figurings are made especially to order. In order that 
 the needle reading may indicate the direction of the telescope, the line joining the 
 >eros of the ordinary compass ring must be in the same vertical plane, with the 
 
44 
 
 line of collimation of the telescope ; and the letters denoting the cardinal points, 
 East and West, must be transposed; i. e., when the letter N is towards the North, 
 the letter W should be towards the East. Of course the needle indicates magnetic 
 north, and in the case of instruments unprovided with means of setting off the local 
 variation of the needle, all the readings of the needle must be corrected for this 
 local deviation. 
 
 If the transit is provided with a variation plate and it is desired to set off the varia- 
 tion by means of the horizontal plate closer than half and quarter degrees say to 
 
 minutes this can be done on the horizontal circle. The verniers of the Transit are 
 set at zero of the graduation and clamped. The zero of the variation ring must also 
 be made to coincide with the stationary pointer. The needle is then released and 
 when at rest the zeros of the variation ring must be made to coincide with the needle 
 ends by the lower tangent screw. To set off the variation, the vernier plate clamp is 
 released and the vernier plate turned so that the telescope (pointing Korth) moves 
 toward the actual East if the variation is West, and toward actual West if the varia- 
 tion is East, until the vernier reads the desired declination on the horizontal circle. 
 The zero of the variation ring is now brought to coincide with the needle ends and the 
 telescope will be pointing to the true North. 
 
 If great accuracy is not desired, the variation may be set off directly on the variation 
 ring in the following manner : If the variation is East, move the zero point of the 
 shifting compass ring the amount of variation for the locality toward the astronomical 
 East (or toward the transposed W. point in the bottom of the compass box). Then 
 clamp shifting ring. When the N. point of needle reads on the graduated ring 
 the telescope will then be pointing to the true North. If the declination is West, turn 
 the shifting ring the proper amount toward the astronomical West, or toward E. 
 point in bottom of compass box. 
 
 The variation plate of our Transits with yoke standard frame has a rack and pinion 
 motion with a capstan-headed nut for clamping when in position. To operate it, 
 slightly unscrew the capstan -h jaded nut at side of milled head, set off the variation, 
 and then again clamp this nut tightly. 
 
 Spirit-Levels. 
 
 The spirit levels, as regards their sensitiveness, should be in strict keeping with 
 the optical power, and the graduations of the instrument, but the quality should be 
 of the best. A level-bubble should move uniformly over the same distance, when 
 the telescope is made to point on two objects alternately, differing slightly in alti- 
 tude, by the leveling screws alone. In change of temperature the bubble should 
 lengthen symmetrically from the center ; and no matter what its length, it should 
 move quickly, without any of the hitching, which is caused usually by a little d-'rt 
 introduced when it is filled. 
 
 Of the three levels attached to the complete transit, the telescope level is the 
 most sensitive. It should be sensitive enough for ordinary leveling, such as good 
 railroad work. The level in front, or at right angles to the standards, should be 
 sensitive enough to make a line plumb by it to any height ; while the third lev** 1 
 on the standard is used in leveling up the instrument, and to establish the 7*** 
 point for the vernier correctly when vertical angles must be measured. 
 
 The test of the fitness of the various levels for the capacity of the instrument 
 should lie in this : that after carefully bi-secting an object in the field of view, in 
 such a position of the instrument that all the levels can be read, and then slightly 
 deranging them all with the leveling screws, the bi-section will be accurately made 
 after restoring the levels to the exact position they before occupied, by the leveling 
 screws a^one. 
 
 Leveling Screws. 
 
 Messrs. C. L. Berger & Sons usually cut their leveling screws with 32 threads to an 
 inch provide the usual four screws in opposing pairs. The plates once set firmly 
 apart by tightening two of these screws on the same side, the leveling of the instru- 
 ment is easily accomplished by turning the two screws of an opposing pair so that 
 both thumbs shall move toward each other (when the bubble will go toward the 
 right), or both thumbs away from each other, when the bubble will move toward 
 the left. Instruments intended for triangulation, i. e., reading to 10" or less, should 
 however be supported on three, instead of upon four screws. In this case the in- 
 strument is rapidly leveled by bringing one level parallel to two of the screws, the 
 other level will now be at right angles to it. Level both levels at the same time 
 by turning one of the screws to which the first level is parallel and the screw 
 which is at right angles to this level. Of course the instrument may now be 
 reversed to guard against non-adjustment of the levels. 
 
45 
 
 Three Leveling: Screws versus Four. 
 
 To the student of the progress in Engineers' field instruments, the question often 
 presents itself as to the comparative merits of an instrument provided with three, 
 over one having four leveling screws. It should be here remarked that the greater 
 portability existing in instruments provided with four leveling screws still com- 
 mends itself to all using the more customary class of instruments. However, the 
 finest class of field instruments, requiring spirit-levels corresponding to the fine- 
 ness of graduation, cannot be advantageously manipulated with tour leveling 
 screws. The results thus obtained would be little better than those obtained with 
 a more ordinary instrument. To insure the full benefit of a finer instrument, such 
 as used in triangulation, the maker will prudently apply three leveling screws, 
 mounted on a feasts larger then is usual in instruments with four screws. So, while 
 four leveling screws have the advantage of greater compactness and less weight 
 three screws have the advantage for closer setting, giving better results. The 
 maker will therefore adapt either the one or the other kind to his instruments aa 
 the c*se may require. 
 
 Quick Leveling Attachment. 
 
 [For illustration seepage 118.] 
 
 As all devices of this kind detract more or less from the stability of an instru- 
 ment, it seems they never have been regarded with much favor by the engineering 
 profession at large. There are cases, however, where the use of such a device, in 
 a mountainous country, or in underground work of a close character, becomes very 
 desirable. Messrs. C. L. Berger <fc Sons' device, unlike devices of a similar kind form- 
 ing a part of the instrument proper, consists of a coupling with a ball and socket joint 
 which can be screwed between the instrument and tripod. As this intermediate 
 piece forms no part of the instrument itself it can be readily attached or detached 
 at will, thus adapting the instrument to the circumstances and to the class of work 
 in hand. For this purpose the threads of this coupling or quick-leveling attach- 
 ment, and those of the instrument and tripod are identical ; and as all their transits 
 and levels with four leveling screws are interchangeable on any of their tripods, 
 one such coupling is sufficient for an engineer's outfit. In fact one extra tripod 
 permanently provided with this quick-leveling attachment may be kept ready for 
 occasional use in an office where there are a number of their instruments. 
 
 To use this quick-leveling attachment proceed as follows: Screw it to the 
 instrument, and then screw both to the tripod in the usual manner, taking care 
 that the coupling becomes firmly fastened thereto. Now to operate it, slightly 
 unscrew the instrument from its hold upon the flange of the coupling by means of 
 the milled edges provided for this purpose, and move it approximately into a level 
 plane, then again screw the instrument firmly to the coupling same as before. 
 This being accomplished, move the instrument over the given point on the ground 
 by means or the centering arrangement described later on, and level up carefully 
 by the leveling screws alone. It will be seen that this quick-leveling attachment 
 is operated entirely independent of the leveling screws or centering arrangement. 
 Of course, when this device is to be used for several days in succession, it is not 
 necessary to detach it from the tripod every time the instrument is to be removed. 
 In such cases the instrument only should be detached from the coupling. When- 
 ever it becomes desirable to detach the coupling from the tripod, it can best be 
 performed by allowing the instrument to remain fastened to the coupling, then by 
 taking hold of the milled edge of the coupling unscrew in the usual manner. In 
 cases where the coupling has been permanently attached to a tripod, the small 
 screws connecting it to the tripod head must first be removed. 
 
 To secure the greatest possible stability to the instrument, the outside diameter 
 of the hollow hemisphere is equal to the distance between the leveling screws of 
 the instrument; and to secure a smooth and ready action, leather washers are 
 provided in the socket which act against the hemisphere. However, when the 
 instrument is clamped to the flange of the coupling these washers recede, and the 
 metal surfaces are brought into direct contact with each other. 
 
 The Gradienter Screw. 
 
 This very convenient attachment consists simply in a screw working against 
 the clamping arm suspended from the horizontal axis, and on the opposite side 
 from the vertical arc. A strong spiral spring is set directly opposite the screw, 
 and presses the clamp arm against the end of it. This screw is cut with great care 
 in a lathe. It has a large silvered head graduated into fifty equal parts. As the 
 screw is turned, the head passes over a small silvered scale, so graduated that one 
 revolution of the screw corresponds to one space of the scale. 
 
46 
 
 Obviously then, the number of whole revolutions made by the screw, in turning 
 the telescope through a vertical arc, can be ascertained from this scale. The clamp 
 arm of the telescope has its clamping screw just above the horizontal axis, in the 
 usual manner. When this screw is free, the telescope may be revolved ; but when 
 it is clamped, the telescope can only be moved by the gradienter screw, which thus 
 takes the place of the ordinary vertical tangent screw. The screw is cut with such 
 a value of a single revolution, as to cause the horizontal cross-line of the telescope 
 to move over a space of jjg of a foot, placed at a distance of 100 feet, when the 
 screw is turned through one of the smallest spaces on its graduated head ; and 
 since there are fifty such spaces on the head, it follows that one revolution of the 
 screw is equivalent to ^ of a foot, at a distance of 100 feet. The numbered gradua- 
 tions on the screw head are then each equivalent to ^ of a foot in 100 feet ; and two 
 entire revolutions of the screw would be twice 55, or 1 foot to the 100. It is readily 
 seen that grades can be established with great rapidity with this screw. It is only 
 necessary after setting the gradienter screw to zero, and leveling and clamping the 
 telescope, to move it up or down as many spaces of the head of the gradienter screw 
 as there are hundredths of feet to the hundred, in the grade to be established. 
 Thus, to establish a grade of l ft 85, the screw head is turned through three whole 
 spaces of the scale, which corresponds to l. ft 50, and through three of the numbered 
 divisions, and five of the shortest ones to make up the entire reading of 1." 85. 
 
 For measuring distances this screw takes the place of stadia lines, and is more 
 convenient ; since for any approximately horizontal distance, the space on an ordi- 
 nary leveling rod expressed in hundredths of feet, included in two revolutions of 
 the screw, will be the number of feet the level rod is distant from the center of the 
 instrument. Thus the difference between two readings of the level rod was 2" . 965 
 when the telescope was moved in altitude through two revolutions of the screw. 
 The rod therefore was distant 296.5 feet. 
 
 It is unnecessary even that a leveling rod be used. A ranging pole or walking 
 stick, or any arbitrary length which can afterwards be measured, will suffice. Thus 
 a stick, which was afterwards measured and found to be 3". 38 long, was found to 
 be subtended by 3^ revolutions of the screw at an unknown distance. 
 
 In this case the distance was 
 
 i|| X 100 = 213 .9 feet. 
 1 58 
 
 In case, however, the distance to be measured is not approximately in the same 
 level plane with the transit telescope, it is necessary to compute the distance, from 
 the readings of the rod. In taking such readings at an altitude, it is customary to 
 incline the rod towards the telescope, and by trial find the least space subtended by 
 two stadia lines. A skilful rod-man will plumb a rod more readily than he can 
 incline it at the proper angle, and a reading of the plumb rod can be taken with 
 jrreater accuracy, and in less time than with the inclined rod ; but it ordinarily 
 involves some additional computing to reduce such vertical readings to horizontal 
 <listances. With the view of reducing the computation to a simple multiplication, 
 the following table is appended with the trignometrical argument on which it 
 depends. The engineer will notice the solution is not rigorously exact, but is suf- 
 ficiently so for all cases in practice. 
 
47 
 
 In the above figure, 
 
 TH = the transit horizontal sight line. 
 The angle HTB = the angle of elevation of the telescope to the foot of the rod 
 
 = E. 
 " " BTA = the angle subtended by any number of revolutions of the 
 
 gradienter screw = G. 
 AB = the length of the rod included by the angle G, when the rod 
 
 is vertical = R. 
 CB is drawn perpendicular to TB. 
 
 Then, CBA = BTH=E TAH = 90 (E + G) 
 
 J5= ( 90 - C E + G) ) cog E cos G - sin E sin G. 
 AB sin (904- G) : ~~ cos G. 
 
 .-. BC=R (cos E tan G sin E.) 
 
 tan G= - where h is the height above a horizontal line, subtended by 
 one revolution of the gradienter screw at a distance a. 
 n is the number of revolutions made in any given case. 
 
 BT = ^rBC = R4-(cosE sinE) 
 
 nh nh ^ a 
 
 .-.BT = R cos E sinE ........ I. 
 
 and 
 
 HT=BT cosE 
 
 .-.HT=R rCos'E ^sin2E ....... II. 
 
 Formulas I and II are general formulas for any gradienter screw. In C. L. 
 Berger & Sons' transits the screw is cut and placed so that when a= 100, for 
 n =2 and A = i, by substitution these formulas become, 
 
 BT = R (100 cos E sin E.) 
 
 HT = R (100 cos 2 E y 2 sin 2 E.) 
 
 Where BT = the direct distance from the center of the horizontal axis of the 
 
 transit to the foot of the vertical rod. 
 
 HT = the horizontal distance from the center of the horizontal axis of the 
 
 transit to the plumb line dropped from the foot of the vertical rod. 
 
 R = the space included on the vertical rod by two revolutions of the 
 
 gradienter screw. 
 
 E = the elevation of the foot of the rod above the horizontal sight line 
 of the telescope. 
 
 When the angle E becomes an angle of depression instead of elevation, then the 
 point B is the upper end of the part of the rod used, A B. The distance B T in 
 this case is the direct distance between the center of the horizontal axis of the tele- 
 scope and the upper reading of the vertical rod in the valley. 
 
 The distance H T is, as before, the horizontal distance between the center of 
 the horizontal axis of the telescope, and the plumb line prolonged in this case 
 upwards from the upper end of the vertical rod. The plumb line in all cases coin- 
 cides with the direction of the rod. 
 
 By means of the following table, it is only necessary to multiply the factor 
 opposite the angle of elevation, by the space included upon a vertical rod by two 
 gradienter screw revolutions, to obtain either the direct or horizontal distance of 
 the center of the horizontal axis of the telescope from the foot of the rod ; or the 
 game distance from the upper reading of the vertical rod in the case of an angle of 
 depression. 
 
48 
 
 Gradienter Screw Table I. 
 
 Factors to be multiplied by the space on the vertical rod expressed in feet and decimals, 
 included in two revolutions of the gradienter screw, to find the distance of the foot 
 of the rod from the center of the horizontal axis of the transit telescope, 
 
 Angle of 
 Elevation 
 
 Factor for the 
 Direct Distance 
 joo cos E- sin E) 
 
 Factor for the 
 Horizontal Dist. 
 (IOQCOS 2 E 1 / 
 sinaE) 
 
 Angle of 
 Elevation 
 . 
 
 Factor for the 
 Direct Distance, 
 loo cos E- sin E) 
 
 Factor for the 
 horizontal Dist. 
 IDC cos* F Vi 
 sin a E) 
 
 o / 
 
 
 
 o / 
 
 
 
 
 
 100.00 
 
 IOO.OO 
 
 15 
 
 9 6 -33 
 
 93-<>5 
 
 I 
 
 99.96 
 
 99-94 
 
 i5 3 
 
 96.09 
 
 9 2 -59 
 
 2 
 
 99.90 
 
 99.84 
 
 16 
 
 95.85 
 
 92.14 
 
 3 
 
 9 9 .8r 
 
 99.67 
 
 16 30 
 
 95-6o 
 
 91.66 
 
 4 
 
 99.69 
 
 99-45 
 
 17 
 
 95-34 
 
 91.17 
 
 5 
 
 99-53 
 
 ' 99-'5 
 
 17 30 
 
 95.07 
 
 90.66 
 
 6 
 
 99-34 
 
 98.80 
 
 18 
 
 94.80 
 
 90.17 
 
 7 
 
 99-'3 
 
 9 8 -39 
 
 18 30 
 
 94-5 1 
 
 89.63 
 
 8 
 
 98.89 
 
 97-93 
 
 J 9 
 
 94.22 
 
 89.09 
 
 9 
 
 98.61 
 
 97.41 
 
 19 30 
 
 93-93 
 
 88.54 
 
 10 
 
 98.31 
 
 96.81 
 
 20 
 
 93' 6 3 
 
 87.98 
 
 10 30 
 
 98.15 
 
 96.51 
 
 20 30 
 
 93.3 2 
 
 87.41 
 
 ii 
 
 97-97 
 
 96.17 
 
 21 
 
 93.00 
 
 86.83 
 
 ii 30 
 
 97-79 
 
 95.82 
 
 21 30 
 
 92.67 
 
 86.22 
 
 12 
 
 97.60 
 
 95-47 
 
 22 
 
 9 2 -34 
 
 85.62 
 
 12 30 
 
 97.41 
 
 95.11 
 
 22 30 
 
 92.01 
 
 85.01 
 
 '3 
 
 97.21 
 
 94-73 
 
 2 3 
 
 91.66 
 
 84.37 
 
 13 30 
 
 97.01 
 
 94-33 
 
 23 3 
 
 9'-3' 
 
 83.75 
 
 H 
 
 96.79 
 
 93.9 2 
 
 24 
 
 90.94 
 
 83.08 
 
 H 30 
 
 96-56 
 
 93-4 8 
 
 24 30 
 
 90.59 
 
 8243 
 
 '5 
 
 9 6 -33 
 
 93-5 
 
 25 oo 
 
 90.21 
 
 81.76 
 
49 
 
 In practically applying this table, it is preferable to take the mean of several 
 readings of the rod in each position of the gradienter screw.* 
 
 Thus, with the target near the foot of the rod, and then moved to correspond to 
 two revolutions of the gradienter screw, three readings hi each position were a 
 follows : 
 
 I. II. 
 
 Altitude 18 2V 
 
 ft 
 
 0.625 
 0.627 
 0.625 
 
 Means, . . . 0.626 3.378 
 
 0.626 
 
 Difference, 2.752 
 
 Factor for direct distance for 18 = 94.80 For Horizontal Distance = 90.17 
 " " 1S30'= 94.51 " " " =89.63 
 
 Differences, . . . =0.29 0.54 
 
 Therefore, the factor, for 18 20' will be for the direct distance 94.80, ?3 of 0.28 
 -a 94.61, and for the horizontal distance, 90.17 2/3 of 0.54 = 89.81. 
 
 Then we have, 2.752 X 94.01 = 260.37 = the direct distance. 
 
 2.752 X 89.81 = 247.15 = the horizontal distance. 
 
 This direct distance being the distance from the position of the foot of the rod 
 or the lower target to the center of the horizontal axis of the telescope,! and the 
 horizontal distance, the one usually desired, that distance reduced to a level line. 
 
 The mean value of two revolutions of the Gradienter Screw in arc. is 34' 23*. 
 Hence the value in arc of one of its smallest divisions on the head is 20" nearly. 
 Vertical angles therefore may be laid off with facility when they are confined to 
 the range ot' the screw. 
 
 To insure at all times accurate results, the telescope axis should revolve free, but without any looseness in 
 the bearings. The engineer should examine these bearings from time to time, and, if necessary, fresh and pure 
 watch oil must be applied. 
 
 To make a measurement with a micrometer screw, its graduated head should be set back slightly, then bring 
 it up to the readings in the same direction in which the measurement must be effected. 
 
 * Should the engineer desire the direct distance between the foot of the rod, and tk* Joint *vrr mkick t*t 
 tivmb-iob is suspended, it may be found by the following formula. 
 
 X = V </ a "I-/ 2 + 'Ifd sin E. 
 or putting it in a shape adapted for logarithmic computation, 
 
 Where x = the distance from the point under the plumb-bob to the foot of the vertical rod. 
 </=the direct distance obtained as above. 
 
 / = the distance from the center of the horizontal axis is to the point under th plumb-bob. 
 f <= the angle of elevation of the foot of the rod, as above. 
 
50 
 
 The subjoined table affords a ready means of expressing any number of reroln- 
 tions, and parts of a revolution, in arc ; and the converse, of degrees, minutes an<? 
 seconds, in revolutions of the screw : 
 
 Gradienter Screw Table II. 
 
 To convert a reading of the Screw 
 into Arc, 
 
 To convert Arc into a reading of 
 the Screw. 
 
 Gradienter 
 Screw. 
 
 Arc. 
 
 Gradienter 
 Screw. 
 
 Arc. 
 
 Arc. 
 
 Gradienter 
 Screw. 
 
 Arc. 
 
 Gradienter 
 Screw. 
 
 RCY. Div. 
 
 f If 
 
 Rev. Div. 
 
 o f ir 
 
 o f rr 
 
 Rev. Div. 
 
 f If 
 
 Rev. Div. 
 
 
 
 O O O 
 
 2 
 
 o 34 2 5 
 
 O O O 
 
 O.O 
 
 o 8 oo 
 
 23.5 
 
 I 
 
 2O 
 
 o 
 
 o 5i 35 
 
 10 
 
 o 0.5 
 
 o 8 30 
 
 o 25.0 
 
 2 
 
 o 40 
 
 4 
 
 i 8 45 
 
 20 
 
 1.0 
 
 o 9 oo 
 
 o 26.0 
 
 d 
 
 1 
 
 5 
 
 i 25 55 
 
 o o 30 
 
 o 1.5 
 
 o 9 30 
 
 o 27.5 
 
 o 4 
 
 1 25 
 
 6 o 
 
 i 43 10 
 
 o o 40 
 
 O 2.O 
 
 O IO OO 
 
 o 29.0 
 
 5 
 
 i 45 
 
 7 
 
 2 O 2O 
 
 o o 50 
 
 o 2.5 ' 
 
 20 00 
 
 i 8.0 
 
 o 6 
 
 2 5 
 
 8 o 
 
 2 17 35 
 
 I OO 
 
 o 3.0 
 
 o 30 oo 
 
 i 37.0 
 
 o 7 
 
 2 25 
 
 9 o 
 
 2 34 45 
 
 o i 30 
 
 4-5 
 
 o 40 oo 
 
 2 19.0 
 
 o 8 
 
 2 45 
 
 10 
 
 2 52 O 
 
 2 00 
 
 o 6.0 
 
 o 50 oo 
 
 2 55-5 
 
 o 9 
 
 3 5 
 
 II O 
 
 3 9 10 
 
 2 30 
 
 o 7-5 
 
 I OO OO 
 
 3 24-5 
 
 O IO 
 
 3 25 
 
 12 O 
 
 3 26 20 
 
 o 3 oo 
 
 o 9.0 
 
 2 00 00 
 
 6 49.0 
 
 2O 
 
 6 50 
 
 13 o 
 
 3 43 30 
 
 033 
 
 o 10,5 
 
 3 oo oo 
 
 10 23.5 
 
 o 30 
 
 IO 2O 
 
 14 o 
 
 4 o 45 
 
 o 4 oo 
 
 12.0 
 
 4 oo oo 
 
 13 48.0 
 
 o 40 
 
 *3 45 
 
 15 o 
 
 4 i7 55 
 
 043 
 
 13-5 
 
 5 oo oo 
 
 17 22.5 
 
 I 
 
 17 jo 
 
 
 
 o 5 oo 
 
 o 15.0 
 
 
 
 I IO 
 
 20 40 
 
 
 
 053 
 
 o 16.0 
 
 
 
 I 20 
 
 24 05 
 
 
 
 o 6 oo 
 
 '7-5 
 
 
 
 1 30 
 
 27 3 
 
 
 
 o 6 30 
 
 o 19.0 
 
 
 
 I 40 
 
 3 55 
 
 
 
 o 7 oo 
 
 o 20.5 
 
 
 
 2 
 
 34 25 
 
 
 
 o 7 30 
 
 O 22. 
 
 
 
51 
 
 Thus, the telescope being leveled, the gradienter screw was turned through a 
 space of 11" T ' 23 dm required the arc : 
 
 11 revolutions, = 3 9' 10" 
 
 20 divisions, =0 6 50 
 
 3 =010 
 
 The whole arc, . . . =3 17' 00" 
 Conversely, it was desired to turn off a vertical angle of 4 35" 
 
 Then we have 
 
 4 0' 0" = 13'"- 48 diT -.0 
 
 30 = 1 37 .0 
 
 50= 15 .0 
 
 40 = 2 .0 
 
 The space on the head of the screw = 16 rev - 2 diT - .0 
 
 The engineer will bear in mind that the examples given are purposely given in 
 detail : that in practice the operations may be mental ones. 
 
 It will be seen that the vertical gradienter can be used for a variety of purposes ; 
 measuring distances, grades, differences of levels, vertical angles, and is a useful 
 check against errors of rod or chain measurement. 
 
 Messrs. C. L. Berger & Sons have also applied the same principle to their hori- 
 zontal tangent screws. By graduating a silver head attached to these screws sub- 
 divisions ot one minute of arc are readily made. 
 
 For constant use with these screws it is better to have a rod with two inovafclt 
 targets, or a rod painted with white and black squares as used in the coast survey. 
 
 Stadia Lines 
 
 The gradienter screw is so universal in its application and can be so readily used 
 for angular, distance or grade measures, that it will generally be found best to have 
 it upon transits designed for current work. There are some cases however where 
 stadia lines are more expeditious in use than the gradienter screw, and give quite 
 as exact results. 
 
 Stadia lines, for instance, where an instrument is to be used for distance measures 
 alone, commend themselves for their greater simplicity. For such work, non-adjust- 
 able lines, in connection with an inverting eye-piece, give the best results. If the 
 lines are adjustable, in the field usage of an instrument they may alter their distance 
 apart ; and there is a rapidity of work with fixed lines, and a rod graduated for 
 telemetrical work, which is not reached in any other way. 
 
 These lines may be webs, or platinum, or they may be ruled on glass. The lat- 
 ter are extremely accurate, but the use of them is necessarily limited in the tele- 
 scopes of field instruments for the following reasons : thin as the glass may be on 
 which the lines are ruled, and intercepting only a small amount of light, yet the film 
 of dampness and dirt soon collecting on it will intercept a great amount of light 
 which in time may become a very serious impediment in the use of the telescope. 
 Another objection to their general adoption consists in the fact that as the image 
 of an object is focussed in the plane of these glass-lines, a portion of the light of the 
 image will become reflected from the polished surfaces of this glass, causing at 
 times a disturbance in the clearness of vision. Besides, this glass-" micrometer," 
 as placed in most telescopes, is very difficult of access and must needs be removed 
 for cleaning, thereby increasing the liability of becoming broken, or detached from 
 its mounting. 
 
 Section 
 showing the 
 Diaphragm 
 natural Size. 
 
52 
 
 Plumbing and Centering Arrangements. 
 
 It now remains to speak of several conveniences of the instrument under con- 
 gideration. By a simple mechanical contrivance the plumb-bob when suspended 
 from the instrument can be set immediately at any desired height. It is suspended 
 directly from the center of the instrument, and not from the tripod head. This 
 precaution shou 1 ' 1 be taken T r >th every instrument, since otherwise, when there is 
 difficulty in setting up an instrument, and the legs are unsymmetrically placed, the 
 plumb-line will not pass through the center of the instrument. 
 
 The instrument is provided with the shifting tripod, better known as the shifting 
 center, by means of which, when the plumb-bob of the instrument is within a fraction 
 of an inch over a point on the ground, it may be brought immediately over it, by 
 moving the body of the instrument on its lower level plate. This is probably the 
 greatest time-saving arrangement which modern makers have introduced in engin- 
 eers' transits. 
 
 Shifting- Center for a Transit with Three Leveling 1 Screws. 
 
 There are several methods of placing a level or transit with three leveling screws 
 upon the tripod head. One is the tribrach style where the leveling screws rest in ra- 
 dial grooves in a triangular shaped foot-plate which screws on to the tripod. This 
 method is used extensively in Europe, but, as the instrument rests only by its 
 own weight in these grooves it is liable to changes in position during use and this in- 
 stability becomes greatly aggravated when the leveling screws become worn. 
 
 Another method in transits is to rest the leveling screws, provided with small bearing 
 cups or washers at their lower ends, directly upon the smooth top surface of the tripod 
 head to allow centering of the instrument over a given point. The pressure of a spiral 
 spring forming part of the instrument fastener is then applied to fix the position of 
 instrument on the tripod head. 
 
 This latter method of connecting a transit to a tripod is very insecure, inasmuch as 
 the slightest change in the position of the instrument, while reading a series of angles, 
 will greatly affect the results. 
 
 Thus it is seen that a transit lacking 
 the necessary stability on its tripod 
 often proves almost useless in the 
 finer field-work. 
 
 Messrs C. L. Berger & Sons make 
 the leveling screws to rest in radial 
 grooves in a separate piece made to 
 slide on the tripod head as shown in 
 cut. A clamp-nut, provided with a 
 large flange and handles, serves to 
 secure this sliding piece to the tripod 
 in any position in the range of its 
 lateral motion. The instrument fas- 
 tener, being part of the tripod proper, 
 has a large cylindrical hole in the 
 threaded stem to allow the hook and 
 chain, suspended directly from the 
 transit center, to pass through and 
 to swing freely in every direction, so 
 that when the plumb-bob is attached 
 its point will be truly in the continu- 
 ation of the vertical center of the 
 instrument. The milled head at the 
 lower end of the fastener serves to 
 screw the latter to the instrument, 
 andamilledheaded nut acting against 
 a spiral spring secures the instrument 
 to the tripod. In use, the pressure 
 of this spring must be sufficient to 
 take up the back lash or any loose- 
 
53 
 
 ness that may exist in the leveling screws; but to secure the necessary stability of the 
 instrument to the tripod, the clamp-nut should be well fastened to the sliding piece. 
 To operate the shifting center, both the spiral-spring and the clamp-nut must be re- 
 leas?d slightly from their hold upon the tripod and the sliding piece, when the instru- 
 ment can be moved over the given point on the ground. This device adds about 2 Ibs. 
 to the weight of the tripod. 
 
 Arrangement for Offsetting at Bight Angles. 
 
 The most common off-set with the transit is one at 90 to the line of sight. 
 Several methods have been proposed for doing this without disturbing the telescope. 
 
 Messrs. C. L. Berger & Sons have a very neat one ; it consists in simply per- 
 forating the horizontal axis, so that by drawing the head back fifteen or twenty 
 inches from one end of the axis, the eye may be placed so that the eye, the hori- 
 zontal axis of the telescope, and a rod set beyond, may be readily placed in the 
 same straight line, at right angles to the line of sight of the telescope, no matter 
 at what altitude the telescope may be pointing. 
 
 In off-setting by the arrangement proposed above, the rod is made plumb by 
 lining it with the plumb-line ot the instrument itself. The advantage of this method 
 is, that it holds equally well for any inclination of the telescope. The disadvantage 
 is, that the engineer is obliged to leave the eye-end of. the telescope at each off-set 
 made 
 
 Setting Up. 
 
 In setting up a transit, push the iron shoe of one leg firmly into the ground, by 
 pressing on the other two legs near the tripod head. Having secured a firm found- 
 ation for this leg, separate the other two legs, at the same time drawing the tripod 
 head toward you. Then set the two remaining legs in the same manner as the first 
 one. If the ground is pretty level, merely noticing that the tripod feet are equi- 
 distant, r ill insure that no unsightly appearance will be ^iven to the leveling screws. 
 If the ground is uneven, however, nothing but practice can produce a graceful 
 position of the instrument. The plumb-bob attached to the instrument should 
 swing within say half an inch of the point on the ground, and the plate on which the 
 leveling screws rest, if possible, should be approximately horizontal, when this 
 stage is completed. 
 
 Now with the level screws not tightened up, after leveling approximately, 
 bring the plumb-bob exactly over the point on the ground, by moving the body of 
 the instrument on its shifting head. Then complete the leveling of the instrument, 
 and it is ready for work. 
 
 The Adjusting of the Transit 
 
 If the instrument is out of adjustment generally, the engineer will find it profit- 
 able to follow the makers in not completing each single adjustment at once, but 
 rather bring the whole instrument to a nice adjustment by repeating the whole 
 series. 
 
 After setting up, bring the two small levels each parallel to a line joining two 
 of the opposing leveling screws. Bring both bubbles to the center of the level tubes, 
 by means of the leveling screws. In doing this, place the two thumbs on the inner 
 edges of the two leveling screws, parallel to the bubbles, and the fore fingers ot 
 each hand on the outer edge. Turn the leveling screws so that both thumbs move 
 inwards or both outwards. In the former case the bubble will move toward the 
 right, in the latter case toward the left. 
 
 Now turn the instrument 180 hi azimuth. If the small levels still hare their 
 bubbles in the center of their tubes, these levels are adjusted, and the circles are 
 respectively as nearly horizontal and vertical as the maker intended them to be. 
 
 If the bubbles, however, are not in the center of their tubes, then bring hem 
 half way back by means of the leveling screws, and the remaining half by means 
 of the adjusting screw at the end of each of the level tubes. 
 
 It may be necessary to repeat this adjustment several times, but when made, the 
 instrument once leveled will have its small levels in the center of their tubes through 
 an entire rotation of the circle. 
 
54 
 
 To make the adjustment for Parallax. This adjustment common to all tele- 
 scopes used in surveying instruments is that of bringing the cross hairs to a sharp 
 focus, at the same time with the object under examination. Point the telescope to the 
 sky, and turn the eye-piece until the cross hairs are sharp and distinct. Since the 
 eye itself may have slightly accommodated itself to the eye-piece, test the adjustment 
 by looking with the unaided eye at some distant point, and while still looking, bring 
 the eye-piece of the telescope before the eye. If the cross hairs are sharp at the 
 first glance, the adjustment is made. Now focus in the usual manner upon any 
 object, bringing the cross hairs and image to a sharp focus by the rack- work alone. 
 A point should remain bi-sected when the eye is moved from one side of the eye- 
 piece to the other. 
 
 To make the vertical cross-line perpendicular to the plane of the hori- 
 zontal axis, simply bi-sect some point at the lower edge 'of the field of view of the 
 telescope by means of the tangent screw and note whether- it continues bi-sected by 
 this cross-line throughout its entire length when the telescope is moved in altitude. If 
 it does not, and the point is to the right of the line in the upper part of the field, the 
 adjustment is made by loosening the four capstan -headed screws, and rotating the 
 reticule in the direction of a left-handed screw, until the point remains bi-sected and 
 then tighten all four adjusting screws. Again, bi-sect the point by means of the tan- 
 gent screw. It should now remain bi-sected throughout the length of the cross-line, if 
 not, this operation must be repeated. 
 
 To adjust the horizontal wire proceed as follows: In transits of our make 
 which have erecting eye-pieces the mechanical construction of the telescope is so 
 perfect that the horizontal wire may be placed in the optical axis by simply placing it 
 in the center of the field of view by the adjusting screws. See diagrams on page 58. 
 However, in telescopes having inverting eye-pieces the horizontal wire can be placed 
 in the optical axis only by rotating the telescope in improvised wyes. 
 
 To adjust the vertical wire which in the transit is the most important. When 
 that is to be alone adjusted in the field, it is usually done according to the following 
 simple directions: Level up the instrument approximately and select two distant points 
 in opposite directions from the instrument, preferably in the same horizontal plane, such 
 that the vertical cross-line will bi-sect them both when the telescope is pointed upon 
 one, and then the telescope is reversed on its horizontal axis. After bi-secting the 
 second point selected, revolve the instrument in azimuth and bi-sect the first point 
 again by means of the tangent screw. Reverse the telescope on its horizontal axis 
 again, and if the second point is now bi-sected the adjustment for collimation of the 
 vertical wire is correct. If it is not bi-sected, move* the vertical wire one-fourth of 
 the distance between its present position and the point previously bi-sected. 
 Again bi-sect the first point selected, reverse the telescope and find a new point pre- 
 cisely in the new line of sight of the telescope; these two points will now remain 
 bi-sected when the instrument is pointed upon them in the manner described above, if 
 the adjustment is correctly made. If the two points are not now both bi-sected, the 
 adjustment must be repeated until this be the case. 
 
 To determine whether the standards are of the same height, suspend a 
 plumb-bob by means of a long cord from a height say of from thirty to forty feet. The 
 plumb-bob may swing in a bucket of water to keep it steady. (Instead of a plumb- 
 line the reflection of a church spire or edge of a tall building or any other convenient 
 object may be viewed in a bucket of water.) Level the instrument carefully, and point 
 upon the plumb-line at its base. If the plumb-line remains bi-sected throughout 
 its entire length when the telescope is moved in altitude, and then the telescope reversed 
 and again made to bi-sect the line throughout its length from its base upward, the ad- 
 justment is correct. Otherwise make the adjustment by means of the capstan-headed 
 screw directly under one of the telescope wyes. Loosen the screws in the pivot caps 
 and turn the vertical adjusting screw right handed to raise the wye bearing one 
 quarter of the error to be corrected. If the telescope's axis is already too high, the 
 vertical adjusting screw should be loosened a little more than needed and then by the 
 screws of the pivot cap the wye bearing should be lowered until it just touches the ver- 
 tical adjusting screw. The screws of the pivot cap must now again be loosened and the 
 wye bearing raised by a right hand turn of the vertical adjusting screw, as explained 
 above, until the telescope's axis is in the correct position. If this is not done the ad- 
 justable bearing is likely to stick and not rest on the adjusting screw, thus causing 
 liability to derangement. The screws in the pivot cap should then be turned down 
 just enough to prevent looseness in the bearings. 
 
 When there are opposing nuts in place of the vertical adjusting screw as is the 
 case in almost all of our transits to secure a more ready, positive and above all a last- 
 ing adjustment then while the modus operandi remains the same, the action of the 
 adjusting nuts to raise or lower the wye bearings is just opposite from that described 
 above. 
 
55 
 
 Instead of using a plumb-line a simpler method having the advantage of not re- 
 quiring the instrument to be leveled up carefully is as follows: Set up the instrument 
 as near as may be convenient to a building, say about 20 feet, in order to get as high an 
 altitude as possible. Level up only approximately, clamp and bi-sect a point at the 
 base by the tangent screw. Then elevate the telescope and find a well-defined object 
 as high as possible, only using the telescope's horizontal axis. Now reverse telescope 
 and move instrument on its vertical center, again clamp, and bi-sect the point at the 
 base. If when the telescope is elevated it bi-sects the high object selected the adjust- 
 ment is correct. If it does not, proceed as described in the above method. 
 
 To adjust the level to the line of col Munition of the horizontal wire one 
 method is to use a sheet of water, or where that is not available, two stakes which are 
 driven with their surfaces in the same level plane.* 
 
 To make the adjustment with the stakes, level up the transit half way 
 between two points lying very nearly in a horizontal line, and say 300 feet apart. 
 Drive a stake at one of these points, place the rod on it and take a reading, first bring- 
 ing the bubble to the middle of its tube. Point the telescope in the opposite direction, 
 again bring the bubble to the middle of its tube, and drive a second stake at the second 
 point selected until the rod held upon the second stake gives the same reading as when 
 held upon the first stake. The tops of these two stakes now lie in the same level line. 
 Take up the transit and set it outside in line, as near as it can be focussed on the 
 first stake and level up. Now read the rod upon the first stake with the bubble in the 
 center and then upon the second. If the two readings agree, and the bubble is in the 
 middle of its tube, the adjustment is correct. If the two readings do not agree, then by 
 means of the telescope's tangent screw elevate or depress the telescope the amount re- 
 quired until the horizontal wire reads the same on the distant rod. Next ref ocus 
 on the near rod, take a reading, then focus on the distant rod and see if the readings 
 are the same, if not, by means of the tangent screw again make the horizontal wire 
 read the same as on the near rod. Repeat this operation until both rods read 
 the same. Now with the horizontal wire bi-secting the distant reading make the ad- 
 justment of the level by its capstan -headed nuts until the bubble is in the middle of its 
 tube when the level will be parallel to the line of collimation. 
 
 Another method of adjusting the attached level to the Transit Telescope 
 will be found on page 63. 
 
 To adjust the verniers of the vertical arc or full circle to read zero, in our 
 Engineer's Transit having the vernier between the legs of the standard. First level 
 up the instrument carefully so that the telescope's bubble will remain in the middle 
 of its tube when turned 180 in azimuth. Then set the zero of the vernier to read 
 within about % minute right with zero of the vertical arc. Then by the vertical 
 tangent screw place both zeros in coincidence and examine the 30' lines and if short 
 the vernier must be moved inwardly so that both of the end lines in the double vernier 
 will read right. If too long the vernier must be moved outwardly until this is 
 attained ; then fasten tightly. Now unloosen only just enough the screws that hold 
 the vertical arc or circle to the horizontal axis, to permit of "a slight shift, and then 
 with the bubble in the center slightly tap one of the spokes of the arc with the handle 
 of the screw-driver, until the zero of the vernier and that of the vertical arc are in 
 coincidence. This accomplished now fasten the vertical arc tightly to its flange. 
 Again level up the telescope as described above and see if the adjustment is correct; if 
 not, again slightly unloosen the vertical arc, tap it into position, repeat the same opera- 
 tion over again until it is correct. 
 
 NOTE. If the vernier for the vertical arc is single, made to read both ways, in 
 reading it proceed to the right or left on the upper line of figures in the direction of 
 the graduation used, and if the coincident line of the vernier is beyond the 15' line, 
 continue on the lower line of figures on the other half of the vernier, so that the whole 
 graduation from 0' to 30' lies in the same direction. The verniers of our vertical arcs 
 are however, made mostly double as described on page 37. 
 
 The Adjustments of the Full Vertical Circle with Double Op- 
 posite Verniers. 
 
 When the vertical circle in the Engineers' Transit is provided with a 
 vernier at eye-end or with double opposite verniers, the adjustment of the 
 vernier zero for normal position should be made by the two opposing capstan-headed 
 screws attached to the vernier frame at side of standard. Then to be lasting and 
 to avoid any strain upon the frame and lugs carrying these adjusting screws, pro- 
 ceed as follows : First level up the instrument so that the bubble of the telescope 
 and plate levels remain in the center of their tubes when vernier plate is turned 180 
 in azimuth; then the zero of vernier "A," at eye-end, should be adjusted by the 
 
 *In general practice one will locate the stakes permanently at some convenient place near the 
 
56 
 
 capstan-headed screw at left to read zero with the circle, by first releasing the opposing 
 screw at right which is now provided with a milled head and then with the finger 
 slightly pressing the vernier frame against the left hand capstan-headed screw, turn the 
 latter until vernier "A" reads zero. Then carefully turn the milled headed opposing 
 screw at right towards the stud until it barely touches. It is best to leave even a 
 little looseness between the stud and opposing screw rather than to have 
 the least strain. (Such minute looseness can be easily felt by the finpers but it 
 should never affect the readings if the looseness is not excessive.) In following 
 this method we reiterate, that the above adjustment will keep for years and 
 there being no strain between the opposing screws and stud, the telescope's 
 axis will always revolve with perfect freedom in the wyes, nor will there be 
 any danger to warp or fracture the frame. 
 
 If the telescope is reversible over the bearings as in the Transit Theodolite, 
 then the vernier frame requires a reversible tangent screw in place of the opposing 
 adjusting screws just explained above. Then before a vertical angle can be taken, 
 the adjustment of the vernier zeros for position must first be made by the vernier 
 frame's tangent screw when the telescope's level bubble is in the center of its gradua- 
 tion. In this latter case it is not always necessary to carefully level up the whole 
 instrument. 
 
 If a vertical circle has a level attached to its vernier frame as in most Tran- 
 sit Theodolites then the adjustment of this level and verniers for position must be 
 made in the following manner: 
 
 Place the telescope in the horizontal plane by means of its tangent screw, then 
 move the vernier frame's tangent screw until the zero line of the double verniers, 
 marked A, is in coincidence with the zero line of the vertical circle, arid now raise or 
 lower the adjusting screw of this level, as the case may be, until the bubble is in the 
 centre of its tube. 
 
 It is now supposed that the zero line of the double opposite verniers, marked B, is 
 also in coincidence with that of the vertical circle. If not, the verniers marked B, can 
 be moved after releasing the capstan-headed screws, until both zero lines on that side 
 of the vertical circle are also in coincidence. However, this is a very laborious pro- 
 ceeding for those uninitiated in this work, and as it cannot always be made quite exact, 
 owing to the mode of mounting the vertical circle on the telescope's axis, it will be found 
 easiest to eliminate errors of excentricity in the graduation of the vertical circle and 
 verniers by reversing the telescope and taking the mean of the readings. The vertical 
 circle is generally graduated from to 90 and back, and the verniers are double, 
 so that angles of elevation and depression can be read with ease and dispatch. 
 
 The striding Level resting on special collars between the 
 
 Standards of the Engineers' and Surveyors' 
 
 Transit, sizes No. 1, 2 and 11. 
 
 In transits reading to minutes and half-minutes, the plate-level in front of the tele- 
 scope is generally sufficiently sensitive to insure good work. However, an instrument 
 of the class as shown and described under No. 1 d, should always be provided with a 
 striding level, to insure a degree of accuracy in keeping with its greater capability. The 
 sensitiveness of this striding level is equal to that of the long level on the telescope. 
 
 Thus it will be seen that in a transit of this description the plate-levels serve only 
 the purpose of leveling up generally, and that in all cases where the objects vary con- 
 siderably in height, the striding level only should be depended on at every sight. The 
 striding le el of this instrument rests on two cylinders of equal diameters,, at points 
 between the standards on the cross-axis of the telescope. As shown in the cut, the 
 striding level can be left on the cross-axis when the telescope is revolved in altitude. 
 To verify the adjustment of the striding level (in other words, to make its axis parallel 
 to the cross-axis) level up the transit and bring the bubble to the middle of its tube, re- 
 verse the striding level on the cylinders and see whether it reads the same; if not, re- 
 move half the error by the leveling screws, the other half by the capstan-headed screws 
 at the end and repeat until corrected. To verify the side adjustment of the level, re- 
 volve the telescope 20 or 30, and note whether the reading of the bubble remains the 
 same, if not, correct the error by the capstan-headed screws at the side. To verify the 
 adjustment of the cross-axis of the telescope for right angles to the vertical axis of the 
 transit, revolve the instrument 180 in azimuth, and assuming that both cylinders, on 
 which the striding level rests, are equal in diameter, a change in the reading of the 
 bubble will indicate double the amount of error. To correct it, remove half the error 
 by the leveling screws, the other half by the Wye adjustment of the standard. 
 
57 
 
 Adjustment of the Improved Transverse Striding Level 
 
 resting- on special collars for the Engineers' and Surveyors' 
 Transits, sizes No. 1, 2 and 11. 
 
 This striding level differs from the one formerly made by us, and referred to in the 
 preceding article, in several respects. It permits of a longer spirit-level in the same 
 length of outer tube so important in this case on account of the short available dis- 
 tance between the collars; and is simpler in design, so that after an adjustment has 
 been once properly performed, barring accidents, it hardly ever needs to be repeated 
 again. 
 
 To make a readjustment: first find out whether the level needs a lateral adjust- 
 ment by placing it on its collars with instrument leveled up, and fastening it by the 
 milled headed nut to the horizontal axis, place the bubble in the center of its tube by 
 the leveling screws, and then elevate and depress the telescope 10 to 20 from 0; note 
 carefully the amount of displacement of bubble, also which one of the two capstan- 
 headed screws (one white and one red, to readily distinguish one from the other) must 
 be moved one-half the error; move screw outwardly if bubble must be moved away from 
 this screw, and inwardly if bubble must be raised towards it to make the level tube 
 laterally parallel to the transverse axis of the telescope. Then move the other adjust- 
 ing screw an equal amount, but in the opposite direction to retain the same height of 
 leg, and repeat this adjustment until one-half the error is corrected. Before operating 
 any of the adjusting screws first remove the level from the collars. 
 
 This accomplished, now make the longitudinal adjustment. Clamp the tele- 
 scope in the horizontal position and reverse the level on its collars; note whether the 
 leg with the screws should be raised or lowered to bring the bubble to the center of its 
 tube, and then turn each screw, alternately, an amount equal to one-quarter the error 
 (inwardly if the leg is to be raised, or outwardly if leg is to be lowered) in order to 
 eliminate one-half the error of the level-tube sought to be corrected. Then again re- 
 verse the level on its collars, and repeat this adjustment if necessary. If the level has 
 been considerably out of adjustment it will be well to again verify the lateral adjust- 
 ment in the manner prescribed for it above, and also to repeat the longitudinal adjust- 
 ment by again following the method just explained until completed. Remember, that 
 if the leg has to be raised, both screws must be moved inwardly towards the telescope, 
 and that if it has to be lowered, both screws must be moved outwardly in equal amounts. 
 This method has been prescribed by us as being the most simple to follow. One some- 
 what versed in making adjustments probably may succeed in making it quicker (if the 
 level is considerably out) by noting mentally the amount of displacement of bubble for 
 the longitudinal and lateral adjustments, and then correcting same simultaneously, or 
 nearly so, with one of the screws alone, by moving it in the desired direction. To ad- 
 just the height of standards see page 54- 
 
 The Adjustments of the Telescope's Axis of Revolution in Transit- 
 Theodolites by means of the Transverse Striding-Level resting 
 on points of contact in the Wyes. 
 
 The striding-level of the finest class of instruments, such as Transit-Theodolites 
 used for triangulation wholly, and Mining Transit used mainly for very steep sighting, 
 will rest directly upon the cylindrical pivots of the transverse axis, at the circle of 
 contact in the wyes. 
 
 Whenever exact vertical motion is desired, the striding-level in such instruments 
 should be depended upon to the exclusion of the front plate-level. The latter is then 
 entirely subordinate to the striding-level and should be depended upon merely for level- 
 ing the instrument approximately. The plate-levels are also useful in indicating 
 quickly any large disturbances of position. When the objects sighted at do not differ 
 much in altitude, the front plate-level is, in these instruments, sufficiently sensitive to 
 give satisfactory results without using the striding-level. 
 
 The adjustment of the transverse axis of revolution. The striding-level 
 having been carefully adjusted, level up the instrument generally with the plate-levels, 
 put the striding-level in position and bring its bubble to the center of its graduation 
 by means of the leveling screws, then turn the instrument 180 on its vertical axis and 
 note whether the bubble of the striding-level remains in the center of the graduation. 
 If it does, the adjustment is correct. If it does not, correct one-half the error by means 
 of the leveling screws, and the other half by means of the wye adjustment of the 
 standard. Repeat the process until the adjustment is correct. Observe also, in ad- 
 justing the wye adjustment of the standards, that it will be best performed and more 
 lasting when the last turns of the lower capstan-headed screw are always applied in 
 an upward direction. 
 
58 
 
 To adjust the line of collimatioii in Erecting and 
 Inverting Telescopes. 
 
 NOTE: To adjust the line of collimation in a telescope showing objects 
 erect, follow the simple rule that the diaphragm bearing the wires must be moved 
 in the direction in which the error is observed (as if to increase the error) ; 
 in telescopes showing objects inverted the wires must be moved in the direction 
 lessening the error observed. See diagrams below. 
 
 Erecting Telescope. 
 
 FIG.I 
 
 Fio.2 
 
 To move the horizontal wire for collimation explained above it must be under- 
 stood that the dotted line in the upper half of the field or view, Fig. 1, shows the hori- 
 zontal wire where it is actually situated on the reticule, but that through the re- 
 versing action of the erecting eye-piece the cross-wire image is reversed and therefore 
 the horizontal wire is seen in the lower half as shown in the diagram. Therefore, if 
 the horizontal wire seen in the lower half of the diagram must be moved upwards, 
 then contrary to the appearance, screw A must be loosened, and B tightened an 
 equal amount in order to bodily move the wire reticule towards the center of the 
 stationary field of view (indicated by the dotted intersection) until one-half of 
 the error is corrected when the wire will be adjusted and appear in the center of the 
 field of view, provided the optical axis of the eye-piece has been previously cen- 
 tered. To move the vertical wire for collimation explained on page 54, remem- 
 ber that the dotted line at the left, Fig. 2, shows the vertical wire where it is actually 
 situated on the reticule, but that through the reversal of the cross-wire image by 
 the use of an erecting eye-piece it is now seen at the right in the field of view in the 
 diagram; therefore, adjusting screw A must be loosened and B tightened an equal 
 amount in order that the reticule will bodily move towards B, when the vertical 
 wire seen at the right will pass towards the center of the stationary field of view 
 (indicated by the dotted intersection) until one-quarter of the error observed is 
 removed, when the wire will be in complete adjustment at the optical axis. 
 
 Inverting Telescope. 
 
 RG.3 
 
 B 
 
 FlG.4 
 
 To move the horizontal wire for collimation, page 54, the observed error must 
 be corrected by moving the wire reticule one-half the amount hi the direction it is 
 lessened, when the telescope is revolved in improvised wyes as in a wye level. Thus, 
 Fig. 3, if the wire must be moved down, A must be loosened and B tightened an equal 
 amount. 
 
 To move the vertical wire for collimation explained above, the observed error 
 must be corrected by moving the wire recticule one-quarter of the amount in the 
 direction it is lessened. Therefore, if the wire must come to the right, A, Fig. 4, must 
 be loosened, and B tightened an equal amount until the object is attained. 
 
39 
 
 THE WYE LEVEL. 
 
 The description of the telescope of the engineer's transit applieg with the fol- 
 lowing modifications to the telescope of this level. 
 
 It has a clear aperture of 13/% inches focus, and is 17 or 18 inches long over all, 
 the sun-shade excluded. 
 
 The bell-metal collars which rest in the wyes are about 10J^ inches apart and 
 1^4 inches in diameter. 
 
 On account of the extreme length of the telescope tube, four capstan-headed 
 screws are provided for centering the eye-piece. 
 
 The object-glass focussing screw is in the middle of the tube. The eye-piece is 
 focussed by turning a milled ring at the eye-end. The level attached to the tele- 
 scope is about 8 inches long, with about 5K inches exposed, and having a scale gradu- 
 ated on glass for reading the position of its bubble. The bubble is ground to a true 
 curvature and barrel form. The sensitiveness of spirit level is graded to the class of 
 work for which the instrument is intended. The level-tube is suspended from the 
 telescope-tube in such a manner that at the object-glass end it can be moved in azi- 
 muth, with reference to the telescope axis, and at the eye-piece end it can be moved 
 in altitude with reference to the same axis. 
 
 Its graduated scale is on the level vial tube, and numbered from 6 to to 5 at, each 
 end of the bubble. 
 
 The level-bar is about 12 inches long over all, and at its two extremities sup- 
 ports the two wyes which rise about 3% inches from its upper surface. One of 
 these wyes is adjustable in altitude. The level-bar is attached to a long conical 
 center of the hardest bell-metal, which may be clamped to the leveling plate, and 
 then a slow motion in azimuth may be given to the telescope, by a slow motion 
 screw which presses the clamping bar against a stiff spiral spring. With the sun- 
 shade on the telescope, the weight is equaly distributed from the center, each way. 
 This is necessary, since a sensitive level, in the nicest work, is affected by any 
 unequal strain, though it may seem to be, practically, imperceptible. 
 
 The base, on which the leveling screws rest, has as great a diameter as porta- 
 bility will permit ; and the leveling screws are cut with a fine thread. These two 
 points add to the ease with which the instrument may be accurately leveled. 
 
 A stop is so arranged that the telescope may be readily set with its horizontal 
 cross-line level, when the instrument is in adjustment. 
 
 The instrument complete is not separable when put into its box. This condition is 
 necessary to protect one of the essential adjustments of the level the adjustment of 
 the wyes from needless derangement. 
 
60 
 
62 
 
 The Adjustment of the Wye Level. 
 
 After the engineer has set up the instrument and adjusted the eye-piece for 
 parallax, as described under the engineer's transit, the horizontal cross-wire had 
 better be made to lie in the plane of the azimuthal rotation of the instrument. 
 This may be accomplished by rotating the reticule, after loosening the capstan-headed 
 screws, until a point remains bi-sected throughout the length of the wire when the 
 telescope is moved in azimuth. In making this adjustment, the level tube is to be 
 kept directly beneath the telescope-tube. When made, the small set screw attached 
 to one of the wyes may be set so that by simply bringing the projecting pin from the 
 telescope against it, the cross-wires will be respectively parallel and perpendicular to 
 the motion of the telescope in azimuth. 
 
 The first collimating of the telescope may be made using an edge of some 
 building, or any profile which is vertical. Make the vertical cross-wire tangent to any 
 such profile, and then turn the telescope half-way round in its wyes. If the vertical 
 cross-wire is still tangent to the edge selected, the vertical cross-wire is collimated. 
 
 To make the adjustment of the horizontal wire, select some horizontal line, 
 and cause the horizontal cross-wire to be brought tangent to it. Again rotate the tele- 
 scope half-way round in its wyes, and if the horizontal cross-wire is still tangent to the 
 edge selected, the horizontal cross-wire is collimated. 
 
 * Having adjusted the two wires separately in this manner, select some well-de- 
 fined point which the cross-wires are made to bi-sect. Now rotate *,he telescope half- 
 way round in its wyes. If the point is still bi-sected, the telescope is collimated. A 
 very excellent mark to use is the intersection of the cross-wires of a transit instrument 
 using same as a collimator. 
 
 To center the eye-piece by the four capstan-headed screws nearest the eye end : 
 This is done by moving the opposite screws in the same direction until a distant object 
 under observation is without the appearance of a rise or fall throughout an entire rota- 
 tion of the telescope in its wyes. The telescope is now adjusted. 
 
 To adjust the spirit level to the telescope, bring the level bar over two of the 
 leveling screws, focus the telescope upon some object about 300 feet distant, and put 
 on the sun-shade. These precautions are necessary to a nice adjustment of the level 
 tube. Throw open the two arms which hold the telescope down in its wyes, and care- 
 fully level the instrument over the two level screws parallel to the telescope. Lift the 
 telescope out of its wyes, turn it end for end and carefully replace it. If the level tube 
 is adjusted, the level will indicate the same reading as before. If it does not, correct 
 half the deviation by the two leveling screws and the remainder by moving the level 
 tube vertically by means of the two adjusting nuts which secure the level tube to the 
 telescope tube at its eye-piece end. Loosen the upper nut with an adjusting pin, and 
 then raise or lower the lower nut as the case requires, and finally clamp that end of 
 the level tube by bringing home the upper nut. This adjustment may require several 
 repetitions before it is perfect. 
 
 To make the lateral adjustment of the spirit level : The level is now to be ad- 
 justed so that its axis may be parallel to the axis of the telescope. Kotate the tele- 
 scope about 20 in its wyes, and note whether the level bubble has the same reading 
 as when the bubble was wider the telescope. If it has, this adjustment is made. If it 
 has not the same reading, move the end of the level tube nearest the object-glass in a 
 horizontal direction, when the telescope is in its proper position, by means of the two 
 small horizontal caps tan- headed screws which secure that end of the level to the tele- 
 scope tube. If the level bubble goes to the object-glass end when that end is to the 
 engineer's right hand, upon rotating the telescope level toward him, then these screws 
 are to be turned in the direction of a left-handed screw, as the engineer sees them, and 
 vice versa. This accomplished the vertical adjustment of the spirit level for parallelism 
 with the line of collimation of the horizontal wire must now again be verified. Having 
 completed this adjustment, the level bar itself must now be made parallel to the axis 
 of the level. 
 
 To make the adjustment of the level bar: Level the instrument carefully 
 over two of its leveling screws, the other two being set as nearly level as may be; turn 
 the instrument 180 in azimuth, and if the level indicates the same inclination, the 
 level bar is adjusted, If the level bubble indicates a change of inclination of the tele- 
 scope in turning 180, correct half the amount of the change by the two level screws, 
 and the remainder by the two capstan-headed nuts at the end of the level bar. Turn both 
 nuts in the same direction, an equal part of a revolution, starting that nut first which 
 is in the direction of the desired movement of the level bar. Many engineers consider 
 this adjustment of little importance, prefering to bring the level bubble in the middle 
 of its tube at each sight by means of the leveling screws alone, rather than to give any 
 great consideration to this adjustment, should it require to be made. 
 
 * See page 58. 
 
63 
 
 THE DUMPY LEVEL. 
 
 (For description and cuts see pages 123 to 129.) 
 
 Adjusting 1 . 
 
 Two-Peg Method. 
 
 A theoretically perfect dumpy level has the same points established that are 
 mentioned under the head of wye level; but since its construction differs from the 
 wye level, the methods of adjustment are not so convenient, resembling closely the 
 adjustment of the transit telescope and its attached level. After attaching the sun- 
 shade remove parallax by pointing the telescope to the sky, and turn the eye-piece un- 
 til the cross hairs are sharp and distinct. Since the eye itself may have slightly 
 accommodated itself to the eye-piece, test the adjustment by looking with the unaided 
 eye at some distant point, and while still looking, bring the eye-piece of the telescope 
 before the eye. If the cross hairs are sharp at the first glance, the adjustment is made. 
 Now focus in the usual manner upon any object, bringing the cross hairs and image to 
 a sharp focus by the rack-work alone. A point should remain bi-sected when the eye 
 is moved from one side of the eye-piece to the other. 
 
 To place the horizontal cross wire at right angles to the vertical center bi-sect 
 some well-defined object such as a chimney top, top of roof, fence-rail or window-sill 
 (the best views are against the sky for a background) and move the telescope on its 
 vertical center. If the horizontal wire bi-sects the point throughout its entire field of 
 view it is adjusted. 
 
 If it does not slightly loosen the four capstan-headed adjusting screws (in the 
 inverting telescope those nearest the eye-piece or the further set from the eye when 
 the telescope shows objects erect) and turn the wire diaphragm until the selected 
 point remains bi-sected when the telescope is moved in azimuth throughout the entire 
 field of view. 
 
 To adjust the level, bring the level over two of its foot screws, and bring the 
 bubble to the middle of its tube by means of the foot screws alone. Revolve the 
 instrument 180 in azimuth, and if the bubble remains in the middle it is adjusted, 
 if it does not, then correct half its deviation by the capstan-headed adjusting screw 
 of the spirit level, and the remaining half by the two foot screws. Repeat the opera- 
 tion over the other two screws, until the instrument may be revolved in any position, 
 and the level bubble will remain in the middle of its tube. 
 
 To adjust the horizontal wire so that the line of sight will be parallel to 
 the spirit level, one method is to use a sheet of water, or where that is not available, 
 two stakes which are driven with their surfaces in the same level plane. 
 
 To make the adjustment with the stakes, set up the level half way between two 
 points lyin? very nearly in a horizontal line, and say 300 feet apart. Drive a stake 
 at one of these points, place the rod on it and take a reading, first bringing the bubble 
 to the middle of its tube. Point the telescope in the opposite direction, again bring 
 the bubble to the middle of its tube, and drive a second stake at the second point 
 selected until the rod held upon the second stake gives the same reading as when 
 held upon the first stake. The tops of these two stakes now lie in the same Level line. 
 
 Take up the level and set it outside in line as near as it can be f ocussed on the first 
 stake and level up. Now read the rod upon the first stake, and then upon the second. If 
 the two readings agree, and the bubble is in the middle of its tube, the collimation is cor- 
 rect. If the two readings do not agree, change the horizontal wire* to read the same 
 on the distant rod by means of the capstan-headed screws near the eye-piece in the 
 inverting telescope and furthest from the eye-piece in the erecting telescope. Refocus 
 on the nearest rod, take a reading, then focus on the distant rod and again by means of 
 the capstan-headed adjusting screws, make the horizontal wire read the same. Repeat 
 this operation until both rods read the same, with the bubble in the middle of its tube. 
 
 The telescope and uprights are in a single casting, which is finished and fitted to 
 the level bar, so that the line of collimation may be permanently parallel to it. 
 
 The dumpy level will then be in adjustment, since the adjustment of its vertical 
 cross line is of no importance. 
 
 Adjustment of the Dumpy Level 1 and attached level of 
 Transit Telescope. 
 
 Two-Peg Method. 
 
 The following method is simple, direct, and geometrically accurate, requiring no 
 approximate measurements from a peg to the center of lens, no trial setting of the tele- 
 scope, no trials to drive a peg just enough and not too far, and no auxiliaries except 
 level-rod and tape or chain. 
 
 Contributed by Prof. R. Fletcher, Thayer School Dartmouth College. 
 * See page 58. 
 
On slightly rising ground locate four points a, 6, c and d, on the same line, nearly, 
 making be = ca, and ad any convenient distance, preferably not much less than ca, and 
 in some simple ratio with it, for ease of calculation afterwards. Set the instrument at 
 c ; take readings A' and B' on a and b respectively, carefully leveling before each sight. 
 Then, unless the instrument is otherwise much out of adjustment, (B' A') is the true 
 difference of level of a and b. 
 
 Next set up at d, level carefully, and take readings A" and B'" on a and b respec- 
 tively. [In strictness the centre of the instrument should not be set over d, but beyond, 
 by an additional distance = principal focal length of the object-lens -j- the distance from 
 that lens to the centre of the tripod. (See the Manual, page 87, Fig. 2.) ] Then (B" 
 A") (B' A') = B'"= error of collimation in the distance ba, that is the error due to 
 the vertical angle between the line of sight and axis of spirit-level. Now, by similar 
 triangles, we have B/ ,, . 6a = BIV : ^ ... B " = B/// x bd , 
 
 ba 
 
 which is the error in the distance bd, and is to be applied to the reading ~B ff . Set the 
 rod to read (B" B 1V ). Then : 
 
 For Adjustment of a Dumpy Level. 
 
 Having first adjusted the spirit-level so that it remains true in all positions about 
 the vertical axis, point the telescope on the rod, properly held at 6, with target set to 
 read (B" B lv ). By means of the capstan-headed screws, raise or lower the horizontal 
 line until it bisects the target. To test the adjustment, set the rod over a, with index 
 reading (B" B IV ) (B' A'), and see if the target is still bisected. 
 
 Adjustment of Attached Level of Transit Telescope. 
 
 The rod being held plumb at b, with target set to read (B" B iv ), move the tele- 
 scope by vertical tangent-screw until the line of sight bisects the target ; clamp securely. 
 Then bring the bubble to the middle of the tube by means of the level- adjusting nuts 
 alone. Test as in the other case. 
 
 KEMARKS. The diagram shows a special case, viz., when (B" A") > (B' A'), 
 or the angle subtended by B vi is one of elevation. If (B" A") = (B' A) the line of 
 sight is already level and no adjustment is needed. If (B" A") < (B' - A?), B* sub- 
 tends an angle of depression, and is to be added to B". In the latter case, if the slope 
 of the ground is slight, the difference (B" A") may be either zero or a very small 
 quantity, positive or negative ; but in all cases it is added algebraically to (B' A') to 
 obtain B" 7 . 
 
 As in all other methods of adjustment, we assume that the maker has done his part 
 so well that the line of collimation will not be disturbed in any movement of the ob- 
 jective for focusing. Let us suppose that the line of collimation is made truly hori- 
 zontal, and that in its prolongation we have set the centres of two targets, one over a 
 and one over 6, the instrument being at d. If now we focus upon the farther target, the 
 image will be bisected by the horizontal spider-line. Then change the focus so as to 
 view the nearer target. If the centre of the objective has not moved truly in the line of 
 collimation, the new image will not be bisected at the focus, and the nearer target will 
 appear to be out of level, when in fact it is not. Hence, since this adjustment requires 
 change of focus, it cannot be made if the above defect, in the movement of the objective, 
 exists. If, however, the distance ad be not too small and the defect alluded to be only 
 slight, the error in changing focus for b and a may be hardly appreciable. The adjust- 
 ment once made approximately, we n^ed not remark that, in the field work, any further 
 error of objective is avoided when taking equidistant sights. 
 
65 
 
 The Surveyor's Solar Attachment. 
 
 Written for this catalogue by'H. C. PEARSONS, C. E., Ferrysburg, Mich. 
 
 The " Solar Attachment," of which the following is a description, is a modification 
 of Peat son's Solar Transit. 
 
 With the view of reducing the weigh f and cost of this attachment, the declination 
 arc is dispensed with, using, in its stead, the latitude arc for setting off the dec- 
 lination. 
 
 And to attain a greater degree of precision, a small telescope with cross-hairs, and 
 a diagonal eye-piece have been introduced in place of the lens-bar and focal-plate. 
 
 This attachment is an appliance to the surveyor's transit for the purpose of 
 finding the astronomical meridian. Combined with that instrument, it becomes 
 purely astronomical in its character indeed, a portable Equatorial, and an Alt.- 
 Azimuth instrument combined, hence a few astronomical definitions seem tc 
 oe requisite. 
 
 In the accompanying cut, the instrument is represented in position for an ob- 
 servation ; and in north latitude (as in these instructions we will suppose the observer 
 to be) the view is as from the west. 
 
 (1.) The line through the vertical axis of the transit represents the pole of 
 horizon, and is called the Vertical. 
 
 The line perpendicular to this represents the Horizon. 
 
 (2.) The transit telescope, having its optical axis in the meridian, and having 
 its south end (whether object-end or eye-end) elevated so that the vertical-arc reads 
 the co-latitude, will have its optical axis in the plane of the equator also; viz. the 
 optical axis of the telescope will then represent the intersection of the plane of the 
 meridian, with that of the equator. This line is called the Equator. 
 
 (3.) The line perpendicular to the equator, that around which the solar 
 telescope revolves, in following the sun in his diurnal course, is the pole of the 
 equator. It is parallel with the earth's axis, and is called the Polar Axis. 
 
 (4.) The arc distance from the equator to the vertical is the Latitude of the ob- 
 server, whence the distance from the vertical to the polar axis, is the Co-Latitude. 
 
 It will be observed that these arcs occur alternately around the entire circle; so 
 that the student should make himself familiar with their relative position with regard 
 to the horizon, and the vertical, in order to avoid mistakes, when setting the polar 
 axis of the instrument up to the pole of the equator. 
 
(5.) Astronomical Triangle. The height of the sun is measured in a plane passing 
 through the " Vertical " and the sun, and is called his Altitude, whence his distance 
 from the " Vertical " is his Co- Altitude. 
 
 In the same manner, the distance from the sun to the "Pole," is his co-dec- 
 lination; and the distance from the ." Vertical " to the pole, is the observer's Co- 
 Latitude. These three compliments form what is called the Astronomical Triangle. 
 
 Thus we have the three sides of a spherical triangle, from which to find the 
 several angles. 
 
 (6.) The angle at the Pole, contained between the meridian of the observer and 
 that passing through the sun, is called the Hour Angle, as it gives the distance from 
 the sun to the observer's meridian, in time or arc, and is usually represented by the 
 letter H. 
 
 (7.) The angle at the "Vertical," or at the observer's zenith, contained between 
 the meridian and a vertical plane passing through the sun, is called the Azimuth 
 Angle, and is usually represented bv the letter Z. 
 
 This angle is the one particularly important to surveyors, as from it the place of 
 the meridian is readily determined. 
 
 Navigator's look for this angle every day, when an observation can be had, and 
 solve the triangle for Z, by one or both of the following equations. 
 
 cosS cos(S p)\| 
 
 ...... (a.) 
 
 . (b.) 
 
 ' v > 
 
 in which 
 
 L = Latitude. Z = the required Azimuth 
 
 d = Declination. p = Polar Distance = 90 d. 
 
 h = Height of the sun's center, corrected for refraction and parallax. 
 
 NOTB. The correction for parallax, which is usually about 6". and never exceeds 9", may be neglected 
 xcept in work of great precision. 
 
 To solve these equations numerically requires much computation, but the Solar 
 Transit solves them for Z, mechanically, with no more computation than that required 
 to deduce the declination for the longitude and local time of the observer, from that 
 given in the Nautical Almanac for the day. 
 
 From the above definitions, it is readily seen that the following conditions, or 
 relation between the parts of the instrument, must be established. 
 
 (A.) The polar axis must be Vertical, when the vertical arc (latitude arc) reads 
 zero, and, consequently, perpendicular to the cross axis of the transit telescope. 
 
 (B.) The horizontal cross-wire of the solar telescope must be parallel with the 
 plane of its rotation around the polar axis; i.e. it must be parallel with the plane 
 of the equator. 
 
 (C.~) The plane passing through the vertical wire and the optical axis of the 
 solar telescope must be at right angles to the cross axis of the solar telescope. 
 
 (D.) The bubble of the level-tube on the solar telescope must be in the middle 
 of its tube, when the optical axis of that telescope is in the plane of the horizon. 
 
 These conditions are obtained by the following 
 
 Adjustments. 
 
 Having attached tL? ' Solar" to the cross axis of the telescope, as directed under 
 the head of "Remarks," and having leveled up the transit (supposed to be in perfect 
 adjustment) carefully, set the vertical or latitude arc to zero, observing that, upon 
 rotating the whole instrument 180 in azimuth, the bubble of the level of the transit 
 telescope is in the middle of the tube. Bring the level bubble of the solar telescope to 
 the middle of the tube by means of the clamp and opposing tangent screws of the 
 solar telescope ; then revolve the solar telescope on its polar axis 180 to see if its 
 bubble remains in the center of its tube : if not, remove half its error by means of the 
 opposing tangent screws, the other half by the milled capstan-headed screws below 
 the base-plate, until it remains in the center of the tube. Repeat if necessary. 
 
 Turn the solar telescope 90 on its polar axis, and by the milled capstan-headed 
 screw level the base-plate and bring the bubble to the center of the tube. Repeat 
 the operation until the bubble of the solar telescope remains in the center of the tube 
 upon revolving the solar telescope around its polar axis. (This condition must be 
 attained before the polar axis can be set to the co-latitude of the observer ; and being 
 .attained it needs no further attention than being examined at times for verification). 
 
67 
 
 The adjustment of the polar axis to be truly at right angles to the line of sight of 
 the main telescope is made by two milled capstan-headed screws and two opposing 
 springs at right angles to each other below the base or leveling plate of the solar 
 attachment. As will be seen in making this adjustment it is not necessary to place 
 the solar telescope parallel or at right angles to the main telescope, but simply in the 
 same vertical plane of each set of leveling screws and springs at the time. This 
 adjustment is made by the manufacturer and thereafter needs only to be examined 
 at times. 
 
 If the adjustments are properly made the bubble of the level of the transit telescope 
 and those of the plate levels on the transit will all be in the center of their tubes, and the 
 vertical arc will read zero. 
 
 Bisect some convenient object, and turn the solar telescope sufficiently to the right 
 or left, around the polar axis, to make the image of the object traverse the field from 
 one side of the tube to the other. The image should remain bisected by the wire, 
 If not, loosen the four capstan-headed screws of the diaphragm till the above condition 
 is attained, and fasten the screws securely, 
 
 The solar telescope showing usually objects inverted, requires the cross-wire dia- 
 phragm to be moved as described on page 58 of Manual. 
 
 Bisect any very distant object in the horizontal plane by the main telescope, and 
 clamp. Then, by means of the clamp and opposing tangent screws on the solar teles- 
 cope, bring its horizontal cross-wire to bisect the same object ; then, by means of the 
 capstan-headed screw of the solar telescope level bring the bubble to the middle of 
 its tube. This being done, the optical axes of the two telescopes will lie in parallel 
 planes for distant objects and the instrument is ready for use. 
 
 All these adjustments are made by the manufacturer, and need to be verified only 
 occasionally. 
 
 Before the solar attachment is available for finding meridian, the observer must 
 know his Latitude, and the sun's Declination for the day and hour of observation, 
 corrected for refraction, whence the 
 
 Reduction of Declination and Refraction, 
 
 The sun's Declination is given for noon of every day in the year, in the Washing- 
 ton and Greenwich Ephemeris of the sun, for those meridians. The maps and charts 
 In use will give the difference of Longitude to all the precision required, and tables in 
 this manual give the required Refraction. 
 
 An example will best illustrate : 
 
 Required a declination table for the different hours of the day for April 25, 1885. 
 Lat. 44 N., and Longitude 97 W. At 15 to the hour, 97 of longitude is about 
 6 1 hours of time, and as this longitude is W., 12 o'clock, or noon, at Greenwich will 
 correspond to 5J^ A. M. at the place of the observer. 
 
 The declination, as given for that day, in the Greenwich Ephemeris, is 13 20' 
 04" N , and is shown to be gaining at the rate of 49" per hour (see column headed 
 Difference for one Hour, with the signs -f- for sun going North, and for SUB 
 going South). 
 
 If now, to the decimation for 5| A.M., we add the hourly rate of change succes- 
 sively, we shall have the declination for the several hours of the day, observing that 
 the first increment is for only half an hour, thus : 
 
 Form of Daily Declination Table. 
 
 APRIL 25, 1885. 
 
 Hourly difference Dec. -f- 49" j Hourly difference + 49" 
 
 Dec. 5 A. M. N. . . . 13 20' 04" + : 1 p. M. N. . 
 
 6 ... 13 20 28 -f 2 
 
 7 ... 13 21 17 4- 3 
 
 4 
 5 
 6 
 7 
 
 10 
 11 
 M. 
 
 13 21 17 4- 
 
 13 22 06 + 
 
 13 22 55 + 
 
 13 23 44 4- 
 
 13 24 33 + 
 
 13 25 22 4- 
 
 Dec. = 13 26' 11" + 
 
 " =13 27 00 -j- 
 
 " =13 27 49 + 
 
 " =13 28 38 + 
 
 " =13 29 27 + 
 
 " =13 30 16 + 
 
 " =13 31 05 + 
 
 The above table must be corrected for the effects of refraction, before it is set off 
 on the vertical arc of the transit. Kefraction increases the apparent altitude of an 
 
 object, and thereby affects the declination of the object ^hn'shing [ the declina - 
 tion when of the Afferent 1 name with the latitude. 
 
68 
 
 From the -(- sign of the " difference" of declination, we see that the decimation is 
 of the same name as the latitude, whence the correction is an increment, and accordingly 
 the -f- sign as suffixed. This sign belongs to the refraction. 
 
 When the object is in the meridian, refraction a.ffects declination by its full 
 amount; but, if both the observer and the object were in the plane of the equator, 
 refraction would have no effect on the object with regard to refraction ; whence, be- 
 tween these limits, only a part of refraction is effective in changing the declination. 
 
 Just what portion is effective, is shown by table II. of this paper. 
 
 Thus, in the given Lat. 44, and for, say 4 hours from noon, the percentage of re- 
 fraction to be applied is .74 of that corresponding to the altitude of the object at the 
 time of observation. The sign ^ to be used must be determined, as above, by con- 
 sidering whether the sun is going north or south at the time. 
 
 This part of the reduction of declination cannot, of course, be made till the alti- 
 tude is found at the time of observation. 
 
 To Find the Latitude. 
 
 Having prepared the declination for the day, as above, level up the transit care- 
 fully. Level the main telescope, observing that the vertical arc reads zero, arid set 
 the polar axis to a vertical position by means of the solar telescope level. 
 
 These points being attained, set the main telescope, pointing south. Then for a 
 
 south [ declination > elevate | the south end of the te 1680 ^ 6 . tin the vertical arc in- 
 dicates the declination thus found. 
 
 Then, having turned the solar telescope into a vertical plane parallel with that 
 containing the optical axis of the main telescope, level it carefully and clamp it. 
 
 A few minutes before the time of the sun's culmination, bring the telescope into 
 the vertical plane passing through the observer and the sun, and "find the sun 1 ' with 
 the solar telescope. This is readily done by varying the altitude when the sun's 
 image will appear on the diagonal eye-piece. 
 
 Having "found the sun," bisect his image with the vertical wire, by varying the 
 azimuth with the tangent screw of the transit plate, or with that of the outer center; 
 and, simultaneously, follow him in altitude the horizontal wire bisecting the image 
 till it ceases to rise, then clamp and read the vertical arc. This reading should 
 be the sum of the co-latitude and refraction, the refraction being that due to the meridian 
 altitude of the sun, which is the algebraic sum of declination and co-latitude. From 
 this reading the latitude is readily deduced. With the latitude and declination 
 known, we are prepared 
 
 To Find the Meridian. 
 
 (a.) As for finding latitude, level up the instrument carefully, the vernier of plate 
 lamped, reading zero. 
 
 (b.) Point the telescope to the sun to find his altitude for the refraction. This 
 can be found with sufficient accuracy by turning the telescope, till the shadow of a 
 pencil held across the end, or till the shadow of the screws on the side, are parallel 
 with the tube. 
 
 (c.) The refraction corresponding to this altitude must be multiplied by the cor- 
 responding coefficient, for the time from noon and the latitude, and applied to the 
 declination, as per instructions above, for the corrected declination. 
 
 (d.) Point the telescope to the south, ^evithi'g ) tne south end for south | decli ' 
 nation, till the vertical arc reads the corrected declination, and clamp the vertical 
 arc. 
 
 (e.) The main telescope being dipped to the corrected declination, level the solar 
 telescope by means of its level, being careful to do so when it is in a vertical plane 
 parallel with that containing the optical axis of the main telescope, for only when it 
 is in this plane can the declination be properly set off. 
 
 (f.) Elevate the south end of the main telescope to the co-latitude, by means of 
 the vertical arc, and turn the telescope approximately into the meridian, by means 
 of tb magnetic needle. 
 
 (g.) " Find the sun " with the solar telescope. This is done by turning the whole in- 
 strument in azimuth, on its outer center, simultaneously with a motion of the solar teles- 
 cope in right ascension, till the sun's image is seen in the eye-end of solar telescope. 
 Bisect the image, as nearly as may be, by the two motions above named clamp 
 and complete the bisection, by both wires, or by the wires forming a square, by means 
 of the transit's lower tangent screw, and by that of the solar telescope. If the image 
 of the sun should be so large that it cannot all be seen from one position of the eye. 
 
look around it by moving the eye around it in such a manner as to see the entire cir- 
 cumference, and bring the cross-wires on the four sides of the image normal to their 
 respective sides, by means of the motion hi azimuth and the motion of the solar 
 telescope, as above described. This being attained, the optical axis of the main teles- 
 cope should be in the astronomical meridian. Refer to an azimuth mark, and repeat 
 the operation. The above is called a direct observation. 
 
 (h.) To make a reverse observation. Having made the direct observation, turn the 
 whole instrument 180 in azimuth, and set the co-latitude off on the opposite side 
 of the vertical arc. Also turn the solar telescope 180 , and proceed as before. The 
 object of repetition is to eliminate personal non-precision and nossible errors in 
 manipulation, while the object of reversing is to eliminate any possible remaining 
 errors of adjustment of the instrument. The prudent surveyor will not trust his work 
 without such verification, and he will take the mean of both observations. 
 
 Remarks. 
 
 (1.) To unscrew the solar attachment from the packing-piece in the box, first 
 release the clamp and tangent screw, and then turn carefully the milled-edged disk or 
 base plate a few turns to the left. To screw the solar attachment to the instrument, 
 turn this milled-edged disk from left to right around the screw on top of the main 
 telescope without revolving the solar attachment. To insure a perfect contact of 
 screw-shoulder against the flange, on which depends the permanency of the adjust- 
 ment of the polar axis to the main telescope, it is necessary that these parts be free 
 from dust, grit, or dirt of any kind. 
 
 (2.) The auxiliary or latitude level, if one is ordered, attaches in the same manner 
 to the end of the cross axis on the side of the vertical circle. 
 
 (3.) The latitude level is used to facilitate during repeated observations the reset- 
 ting of the polar axis to the co-latitude, assuming that the polar axis has been pre- 
 viously set to be at right angles to the main telescope by its milled capstan-headed 
 screws and the solar level, the polar axis being placed in its position for an observation 
 with more facility and precision with this level than by reading the vertical arc. 
 
 (6.) The latitude having been found for the initial point of a survey, it may be 
 found for other points within moderate limits by allowing 92 chains of northing or 
 southing for 1' of latitude. 
 
 (7.) The object of bringing the main telescope into the meridian by means of 
 motion on the outer spindle is to have the zero line of the horizontal plate hi the 
 meridian, so that the azimuth or bearing of lines can be referred to that line. 
 
 (8.) If for any cause one is obliged to work with an uncertain latitude, it is better 
 
 to so with the sun as far from the meridian as practicable, for the following 
 reasons : 
 
 It is only when the sun is in the pole of the meridian that it has its maximum 
 efficiency in pointing out the direction of the meridian. 
 
 Hence a large hour-angle, and a small declination, are conducive to the elimination 
 of errors resulting from an incorrect latitude. 
 
 Indeed, with the sun precisely in the pole of the meridian, the meridian is deter- 
 mined independently of latitude. 
 
 (9.) In making the several adjustments, or rather in verifying them, the student 
 should have a true meridian established by some other means than by the " solar 
 transit," as from the North Star, by some of the methods given in works on surveying. 
 He should compare the results of his observations with this meridian at different 
 times in the day, and under different states of the atmosphere, till he has learned any 
 peculiarity of the instrument and the utmost precision obtainable with it, as well as the 
 ordinary limit of non-precision, 
 
 NOTE. The great utility of this auxiliary, or level attachment, is seen in the setting of grades. Two of 
 these levels being applied to the telescope of a pivot-levelling instrument one on each side or one on each 
 nd of the cross-axis of a transit telescope, and one of them being adjusted to the up, the other to the down 
 , the engineer may work in either direction on his grade with the same facility that he would on a level 
 
 c 8 
 
 to dc 
 
70 
 
 Degree of Precision Required. 
 
 (10.) This, of course, depends on the character of the work to be done. In the 
 U. S. Public Land Surveys, which are, without question, conducted on the best plan 
 the world can afford, only compass lines are required. As a consequence, a wide 
 margin for non-precision is given. 
 
 t In sub-dividing a block of townships, the surveyor in coursing a random of 6 
 miles, is required to make his objective point within 3 chains. Charging the half 
 of this error to lineal measurement, we find the error of coursing must be within 10* 
 of the true course. 
 
 (11. j In Manitoba, the authorities, having fallen in love uith our system of Pub- 
 lic Land Surveys, have adopted it ; but they require greater precision. They re- 
 quire clear transit lines, projected with the best six-inch silver lined instruments, 
 graduated to 10". 
 
 In coursing a 6 mile random in the sub-division of a township, the surveyor 
 must make his objective point within one chain, in order to save reviewing his work, 
 charging, as before, one half of this error to the lineal measurements, we find the 
 maximum error allowed in coursing to be between 3* and 4'. 
 
 (12) With the " New Solar," as manufactured by Messrs. C. L. Berger & Sons, 
 the surveyor will be surprised and delighted to see the facility and certainty with 
 which he can bring his work far within the above limit. 
 
 Inclination of the Meridian. 
 
 (13.) In projecting arcs of a great circle with the "solar transit," it is of ths 
 utmost importance that the surveyor be able to tell the inclination of the meridians for 
 any latitude, and for any distance of eastings or westings. 
 
 As this problem is not treated in elementary works on 
 surveying, perhaps the few following hints may be of use 
 to the young student. 
 
 In the following figure, let the two arcs A G, and B G 
 be two arcs of a quadrant of the meridian, 1 of longitude 
 apart. Let A B = the arc of one degree of longitude on 
 the equator = 69.16 miles. 
 
 Let D E be an arc of longitude on any parallel of 
 latitude. Also, let E H and D H be the tangents of those 
 meridians meeting in the earth's axis produced, and cor- 
 responding to the parallel of latitude D E. 
 
 Then the line E F = D F = cos L = cos A D or B E. 
 Also, the angle D F E = l,and the angle D H E=the 
 inclination of the meridians, which is the angle we wish 
 to find, and which we will represent by X. And, because 
 the two triangles F D E and D H E are on the same base 
 E D, and isosceles, their vertical angles vary inversely as 
 their sides ; and we have the equation, 
 
 1XEF=XXEH, But 
 
 E F = cos L, and E H = cot L, hence 
 
 X cot L = l cos L, or 
 
 X = cos L -4- cot L = sin L, (a) 
 
 That is to say, 
 
 The inclination of the meridians for any difference of longitude, varies as the sine 
 of the latitude. 
 
 (14.) Since the sine of the latitude is the inclination in decimals of a degree, for 
 one degree of longitude, if we multiply by 3600" we shall have the inclination in 
 seconds of arc. Then, if we divide this by the number of miles in one degree of 
 longitude on that latitude, we shall have the inclination due to one mile on that 
 parallel. Thus, for 
 
 Latitude 43 log. sine = 9.833783 
 
 Multiply by 3600" " = 3.556303 
 
 3.390086 
 
 Divide by 5066, = 1 long, on that L, log. 
 4S".46 = inclination for one mile of long. 
 
 1.704682 
 1.685404 
 
71 
 
 (15.) The use of the Inclination, as found by the preceding article, is to show 
 the surveyor how much he must deflect a line of survey from the due east or west, 
 to have it meet the parallel at a given distance from the initial point of the survey, 
 for it will be remembered that a parallel of latitude is laid out as a curve lying in a 
 horizontal plane and having the cotangent of the latitude for its radius. And the 
 line due east or west is the tangent of the curve. 
 
 Thus, on latitude 43, I wish to project a six-mile line west, for the southerly 
 line of a township. 
 
 Remembering that in an isosceles triangle, the angle at the base is less than a 
 right angle by half the angle at the vertex, I deflect my line towards the pole by the 
 inclination due to three miles, or in this case 48" .46 X 3 = 2' .25", i. e., Deflection 
 = Yz Inclination. 
 
 (16.) Table No. Ill, which was computed from the formula (a) Art. 37, gives the 
 Inclination for one mile, and for six miles on any parallel, from 10 to 60 of latitude; 
 also the Convergency for six miles, on any latitude. 
 
 (17.) The Convergency of the meridian is readily found for any given distance 
 from the corresponding inclination, by multiplying the Sine of the inclination by 
 the given distance. 
 
 Thus, for latitude 43, the inclination for one mile is 4S / '.46; the sine of which is 
 .000235. This, multiplied by the number of links in a mile, which == 8000, we have 
 the convergency for one mile,= l.S8 links. 
 
 Multiplying this by the number of miles in atownship,=36, and we have the 
 convergency for a township = G7.C8 links. In this manner were the convergencies 
 of table III computed. 
 
 (18.) Deflection of Mange-Lines from meridian. The second column of table III 
 shows the surveyor how much he must deflect the range lines between the several 
 sections of a township from the meridian, in order to make the consecutive ranges 
 of sections in a township of uniform width, for the purpose of throwing the effects 
 of "convergency" into the most westerly range of quarter sections agreeably to law. 
 Thus, say between 45 and 55 of latitude, the inclination is practically 1' for 
 every mile of easting or westing. Then, bearing in mind that in the U.S., sur- 
 veys arc regarded as projected from the East and South to the West and North ; the 
 surveyor must project the first range-line between the sections of a township in those 
 latitudes, V to the left of the meridian. 
 
 The second, 2' ; the third, 3' ; and so on to the fifth, which must be 6' to the left 
 of the meridian on the east side of the township. 
 
 By this means all the convergency of the township is thrown into the sixth, or 
 westerly range of sections, as the law directs. 
 
 The fourth column of the above table shows the amount of this convergency. 
 This column is also useful in sub-dividing a block of territory embraced by two 
 "standard parallels" and two "guide meridians" into townships. Thus, starting a 
 meridian from a standard parallel on latitude 43 N, for the western boundary ol 
 a range of township, say the first one west from the guide meridian, and running 
 North, say 4 townships, the surveyor must make a point that is East of the six-mile 
 point on the northern "standard parallel" 4 X 67.7 links = 270.8 links, The second 
 meridian should fall 8 X 67.7 links to the right of the twelve-mile point, etc. 
 
 (19.) The Variation of the Needle. This is easily determined by noting th 
 reading of the needle when the solar transit telescope has been brought into th 
 meridian. 
 
 Observation for Meridian with the Berger Solar 
 
 Attachment. 
 
 Written for this catalogue by GEO. L. HOSMER, Massachusetts Institute of Technology. 
 
 CALCULATION. 
 
 Before beginning the observations the following computations must be made. 
 1. Take from the Nautical Almanac (table II, for the month) the sun's "apparent 
 declination," for Greenwich Mean Noon of the date of the observation. If it is 
 north prefix a -f sign, if south, a sign. 2. On the same line, in the next 
 column to the right is the "difference for one hour," with the proper algebraic 
 sign before it. 3. The local time corresponding to Greenwich Mean Noon maj be 
 found by subtracting the west longtitude of the place from 12h, e. g. at the ?6th 
 meridian, this would give 7h A.M.; at the 90th, 6h A. M., etc. 4. Next compute 
 the declination for each hour by adding algebraically the "difference for 1 h" 
 to the decimation for the preceding hour. 6. Next correct each of these declina- 
 
72 
 
 tions for refraction, using the tables given in this catalogue, or such as are given 
 in Prof. J. B. Johnson's work on surveying. Careful attention should be paid to 
 signs. 
 
 We <vill assume for the present that the latitude is known, and proceed to the 
 description of the 
 
 FIELD OPERATIONS. 
 
 1. Lay off on the vertical arc the declination setting for the time of observation, 
 tipping the telescope in such a direction that the small telescope will point above 
 or below the equator according as the declination is N. or S. 2. Lev< 1 the small 
 telescope by means of its attached level, and then clamp it. 3. Next change the 
 setting of the vertical circle so that it reads the co-latitude of the place. 5. Using 
 both tho horizontal and the equatorial motions, point the small telescope at the 
 sun, making the four segments cut off by the cross hairs equal. The main tele- 
 scope is now in the meridian. To be certain that the settings are correct wait a 
 few moments and see if the disc follows the equatorial wires perfectly. Both 
 plates should be clamped while the image is in the center of the field. The line 
 may then be brought down to the ground and marked. 
 
 EXAMPLE OF COMPUTATION. 
 
 Long. 5h. West., Lat. -f 40. Jan. 10, 1900. 
 Decl. for Gr. Mean Noon = 21 59' 04". 
 Diff. for Ih. = -f 22".25. 
 
 TIME. DECLINATION. REFRACTION SETTING. 
 
 7h. A.M. 21 59' 04" 
 
 8 58 42 5' 40" 21 53' 02" 
 
 9 " 58 20 2' 51' 21 55 29 
 
 10 " 57 57 2' 07" 21 55 50 
 
 11 67 35 1' 51" 21 55 44 
 
 12 M. 57 13 (!' 47") (21 55 26) 
 
 1 P.M. 56 51 1' 51" 21 55 00 
 
 2 " 56 28 2' 07" 21 54 21 
 
 3 " 56 06 2' 51" 21 53 15 
 
 4 " 55 44 5' 40" 21 50 04 
 
 The co-latitude may be found by measuring the altitude of the sun's lower 
 limb at noon, i.e. by measuring the maximum altitude. This angle must be cor- 
 rected for refraction, semi-diameter and declination. The result is the co latitude. 
 The co-latitude may also be found, very nearly, as follows: Make the angle be- 
 tween the t elescopes equal to the declination setting at noon in the same way as for 
 any other hour. Bring the telescopes into the same vertical plane, and point the 
 small telesoope at the sun. By varying the elevation angle of the main telescope 
 keep the small telescope pointing at the sun until a maximum elevation is reached. 
 This angle is the co-latitude, already corrected for refraction, semi-diameter and 
 declination. This method is not quite as accurate as the former. 
 
 A TEST. 
 
 The following observations were made by the writer with the Berger Solar 
 Attachment. The plates were clamped at zero degrees and the meridian found by 
 solar observation. An angle was then turned to a mark *^ mile away. The re- 
 sults are as follows : 
 
 TIME. Az. ANGLE 
 
 A M. 
 
 8:30 240 07' 
 
 8:40 
 8 :50 
 
 9 :00 06 
 
 P.M. 
 
 3:23 240 05' 
 
 3 :30 03 
 
 Clouds prevented further observations. 
 
 The true azimuth as found afterward by an observation on Polaris was 240 05' 
 30". 
 
73 
 
 Table I. 
 
 Mean Refraction of Celestial Objects for Temperature 5O, 
 and Pressure 29*6 inches. 
 
 Alt. 
 
 Refr, 
 
 Alt. 
 
 Refr. 
 
 Alt. 
 
 Refr. 
 
 Alt. 
 
 Refr. 
 
 Alt. 
 
 Refr. 
 
 O f 
 
 O O 
 
 ' If 
 
 33 o 
 
 f 
 
 5 30 
 
 ' // 
 
 9 8 
 
 o f 
 12 
 
 ' tr 
 
 4 2 3 
 
 / 
 
 23 o 
 
 ' If 
 2 14 
 
 / 
 
 46 o 
 
 ' tf 
 
 55 
 
 IO 
 
 31 22 
 
 40 
 
 854 
 
 20 
 
 4 1 6 
 
 20 
 
 2 12 
 
 47 o 
 
 53 
 
 20 
 
 2 9 50 
 
 50 
 
 8 41 
 
 4 
 
 4 9 
 
 40 
 
 2 10 
 
 48 o 
 
 o 5i 
 
 30 
 
 28 23 
 
 6 o 
 
 8 28 
 
 13 o 
 
 4 3 
 
 24 o 
 
 2 8 
 
 49 o 
 
 o 49 
 
 40 
 
 27 o 
 
 10 
 
 S 15 
 
 2O 
 
 3 57 
 
 20 
 
 2 6 
 
 5 
 
 o 48 
 
 5 
 
 25 4 2 
 
 20 
 
 8 3 
 
 4 
 
 3 5* 
 
 4 
 
 2 4 
 
 5 1 
 
 o 46 
 
 I 
 
 24 29 
 
 3 
 
 7 5 1 
 
 14 o 
 
 3 45 
 
 25 o 
 
 2 2 
 
 52 o 
 
 o 44 
 
 10 
 
 23 20 
 
 40 
 
 7 4 
 
 20 
 
 3 4o 
 
 20 
 
 2 
 
 53 o 
 
 43 
 
 20 
 
 22 15 
 
 50 
 
 7 3 
 
 4 
 
 3 35 
 
 4 
 
 1 58 
 
 54 
 
 o 41 
 
 3 
 
 21 15 
 
 7 o 
 
 7 20 
 
 15 
 
 3 30 
 
 26 o 
 
 I 56 
 
 56 o 
 
 o 38 
 
 40 
 
 20 18 
 
 IO 
 
 7 'I 
 
 20 
 
 3 26 
 
 20 
 
 i 55 
 
 58 o 
 
 o 35 
 
 50 
 
 '9 25 
 
 20 
 
 7 2 
 
 40 
 
 3 21 
 
 4 
 
 i 53 
 
 60 o 
 
 o 33 
 
 2 
 
 1835 
 
 30 
 
 653 
 
 16 o 
 
 3 17 
 
 27 o 
 
 i 5i 
 
 62 o 
 
 o 30 
 
 IO 
 
 1748 
 
 40 
 
 645 
 
 20 
 
 3 12 
 
 3 
 
 i 49 
 
 64 o 
 
 o 28 
 
 2O 
 
 '7 4 
 
 50 
 
 637 
 
 40 
 
 3 8 
 
 28 o 
 
 i 47 
 
 66 o 
 
 o 25 
 
 30 
 
 1 6 24 
 
 8 o 
 
 6 29 
 
 17 o 
 
 3 4 
 
 30 
 
 i 45 
 
 68 o 
 
 o 23 
 
 4 
 
 '5 45 
 
 10 
 
 6 22 
 
 20 
 
 3 i 
 
 29 o 
 
 i 42 
 
 70 o 
 
 21 
 
 5 
 
 '5 9 
 
 20 
 
 6 15 
 
 40 
 
 2 57 
 
 3 
 
 i 38 
 
 72 o 
 
 o 18 
 
 3 o 
 
 H36 
 
 30 
 
 6 8 
 
 18 o 
 
 2 54 
 
 31 o 
 
 ' 35 
 
 74 o 
 
 o 16 
 
 10 
 
 14 4 
 
 40 
 
 6 i 
 
 20 
 
 2 51 
 
 3 2 o 
 
 1 3 1 
 
 76 o 
 
 o 14 
 
 20 
 
 '334 
 
 50 
 
 5 55 
 
 4 
 
 2 47 
 
 33 o 
 
 i 28 
 
 78 o 
 
 12 
 
 3 
 
 13 6 
 
 9 o 
 
 548 
 
 19 o 
 
 2 44 
 
 34 o 
 
 i 24 
 
 80 o 
 
 10 
 
 40 
 
 12 40 
 
 IO 
 
 5 42 
 
 20 
 
 2 41 
 
 35 o 
 
 I 21 
 
 82 o 
 
 o 8 
 
 50 
 
 12 15 
 
 20 
 
 536 
 
 40 
 
 2 38 
 
 36 c 
 
 i 18 
 
 84 o 
 
 O 
 
 4 o 
 
 'I 51 
 
 3 
 
 5 3i 
 
 20 O 
 
 2 35 
 
 37 
 
 i 16 
 
 86 o 
 
 o 6 
 
 10 
 
 II 29 
 
 40 
 
 5 25 
 
 20 
 
 2 32 
 
 38 o 
 
 i 13 
 
 88 o 
 
 2 
 
 20 
 
 ii 8 
 
 5 
 
 5 20 
 
 4 
 
 2 29 
 
 39 o 
 
 I 10 
 
 90 o 
 
 
 
 3 
 
 10 48 
 
 10 
 
 5 i5 
 
 21 O 
 
 2 27 
 
 40 o 
 
 i 8 
 
 
 
 40 
 
 10 29 
 
 20 
 
 5 5 
 
 20 
 
 2 25 
 
 41 o 
 
 i 6 
 
 
 
 5 
 
 10 II 
 
 4 
 
 4 5 6 
 
 40 
 
 2 23 
 
 42 o 
 
 i 3 
 
 
 
 5 
 
 9 54 
 
 II O 
 
 4 47 
 
 22 O 
 
 2 20 
 
 43 o 
 
 i i 
 
 
 
 '10 
 
 93S 
 
 20 
 
 4 39 
 
 20 
 
 2 l8 
 
 44 
 
 59 
 
 
 
 20 
 
 9 2 3 
 
 40 
 
 4 3i 
 
 4 
 
 2 IO 
 
 45 o 
 
 o 57 
 
 
 
74 
 
 Correction to the Mean Refraction given in the 
 preceding Table. 
 
 & 
 
 Height of the Thermometer. 
 
 
 20 
 
 24 
 
 28 
 
 32 
 
 3 6 
 
 40; 
 
 44; 
 
 
 52 
 
 56 
 
 60 
 
 K 
 
 68 
 
 72; 
 
 76 
 
 , 8c C 
 
 
 
 2 4 
 
 2 18 
 
 1 55 
 
 i 33 
 
 I II 
 
 5 1 
 
 3l" 
 
 +'' 
 
 10 
 
 IO 
 
 2 9 
 
 // 
 4 8 
 
 / // 
 
 * 7 
 
 ' . " 
 
 1 25 
 
 143 
 
 2 I 
 
 219 
 
 20 
 
 2 25 
 
 2 5 
 
 i 44 
 
 i 24 
 
 1 4 
 
 46 
 
 28 
 
 9 
 
 9 
 
 26 
 
 44 
 
 i i 
 
 117 
 
 133 
 
 I 49 
 
 205 
 
 o 40 
 
 2 II 
 
 i 53 
 
 1 34 
 
 i 16 
 
 58 
 
 42 
 
 25 
 
 8 
 
 8 
 
 2 4 
 
 39 
 
 55 
 
 I 10 
 
 I2 4 
 
 138 
 
 153 
 
 I 
 
 1 59 
 
 1 43 
 
 i 25 
 
 r 9 
 
 53 
 
 38 
 
 23 
 
 8 
 
 7 
 
 21 
 
 36 
 
 5 
 
 1 3 
 
 117 
 
 130 
 
 M3 
 
 I 20 
 
 i 48 
 
 1 33 
 
 i 17 
 
 1 3 
 
 48 
 
 34 
 
 21 
 
 7 
 
 6 
 
 19 
 
 3 3 
 
 45 
 
 57 
 
 1 9 
 
 I 21 
 
 i 33 
 
 1 40 
 
 i 39 
 
 i 25 
 
 i ii 
 
 57 
 
 44 
 
 3 1 
 
 18 
 
 6 
 
 6 
 
 18 
 
 30 
 
 41 
 
 52 
 
 1 4 
 
 1 '5 
 
 125 
 
 2. 
 
 1 3 1 
 
 i 18 
 
 1 5 
 
 53 
 
 39 
 
 2 9 
 
 1 7 
 
 6 
 
 5 
 
 16 
 
 27 
 
 37 
 
 48 
 
 58 
 
 i 8 
 
 i 18 
 
 3 
 
 i ii 
 
 i i 
 
 5 1 
 
 4 1 
 
 3 2 
 
 22 
 
 J 3 
 
 ^ 
 
 4 
 
 '3 
 
 21 
 
 3 
 
 38 
 
 46 
 
 54 
 
 i i 
 
 4 o 
 
 58 
 
 49 
 
 4 1 
 
 33 
 
 26 
 
 18 
 
 ii 
 
 4 
 
 4 
 
 10 
 
 17 
 
 24 
 
 3 1 
 
 37 
 
 44 
 
 5 
 
 c o 
 
 48 
 
 
 35 
 
 28 
 
 22 
 
 16 
 
 9 
 
 3 
 
 3 
 
 9 
 
 H 
 
 20 
 
 26 
 
 3 1 
 
 36 
 
 40 
 
 6 o 
 
 
 35 
 
 30 
 
 24 
 
 19 
 
 '3 
 
 8 
 
 3 
 
 2 
 
 7 
 
 12 
 
 17 
 
 22 
 
 26 
 
 3 1 
 
 35 
 
 7 o 
 
 36 
 
 3 1 
 
 26 
 
 21 
 
 16 
 
 12 
 
 7 
 
 2 
 
 2 
 
 6 
 
 10 
 
 H 
 
 '9 
 
 23 
 
 27 
 
 31 
 
 8 o 
 
 3 2 
 
 27 
 
 23 
 
 19 
 
 15 
 
 10 
 
 6 
 
 2 
 
 2 
 
 5 
 
 9 
 
 
 16 
 
 20 
 
 24 
 
 27 
 
 9 
 
 28 
 
 24 
 
 20 
 
 16 
 
 '3 
 
 9 
 
 5 
 
 2 
 
 2 
 
 5 
 
 8 
 
 ii 
 
 '4 
 
 18 
 
 21 
 
 24 
 
 10 
 
 26 
 
 22 
 
 18 
 
 15 
 
 12 
 
 8 
 
 5 
 
 2 
 
 
 4 
 
 7 
 
 10 
 
 13 
 
 16 
 
 1 9 
 
 22 
 
 12 
 
 21 
 
 18 
 
 15 
 
 13 
 
 10 
 
 7 
 
 4 
 
 I 
 
 
 4 
 
 6 
 
 9 
 
 ii 
 
 13 
 
 16 
 
 18 
 
 H 
 
 18 
 
 16 
 
 13 
 
 ii 
 
 8 
 
 6 
 
 4 
 
 I 
 
 
 3 
 
 5 
 
 7 
 
 9 
 
 ii 
 
 M 
 
 16 
 
 16 
 
 16 
 
 J A 
 
 12 
 
 9 
 
 7 
 
 5 
 
 3 
 
 I 
 
 
 3 
 
 5 
 
 6 
 
 8 
 
 IO 
 
 12 
 
 H 
 
 18 
 
 M 
 
 12 
 
 10 
 
 8 
 
 6 
 
 5 
 
 3 
 
 I 
 
 
 2 
 
 4 
 
 6 
 
 7 
 
 9| 10 
 
 12 
 
 20 
 
 '3 
 
 II 
 
 9 
 
 7 
 
 6 
 
 4 
 
 2 
 
 I 
 
 
 2 
 
 4 
 
 5 
 
 6 
 
 8 
 
 9 
 
 ii 
 
 25 
 
 10 
 
 8 
 
 7 
 
 6 
 
 5 
 
 3 
 
 2 
 
 I 
 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 3 
 
 8 
 
 7 6 
 
 5 
 
 4 
 
 3 
 
 2 
 
 I 
 
 O 
 
 I 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 35 
 
 7 
 
 6} 5 
 
 4 
 
 3 
 
 2 
 
 I 
 
 
 
 
 
 I 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 6 
 
 40 
 
 6 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 I 
 
 
 
 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 45 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 I 
 
 
 
 o 
 
 I 
 
 I 
 
 2 
 
 2 
 
 3 
 
 3 
 
 4 
 
 5 
 
 4 
 
 3 
 
 3 
 
 2 
 
 2 
 
 I 
 
 I 
 
 o 
 
 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 3 
 
 55 
 
 3 
 
 3 
 
 2 
 
 2 
 
 2 
 
 I 
 
 I 
 
 
 
 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 3 
 
 60 
 
 3 
 
 2 
 
 2 
 
 2 
 
 I 
 
 I 
 
 I 
 
 
 
 o 
 
 O 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 2 
 
 65 
 
 2 
 
 2 
 
 2 
 
 I 
 
 I 
 
 I 
 
 O 
 
 
 
 o 
 
 
 
 I 
 
 I 
 
 I 
 
 I 
 
 2 
 
 2 
 
 7 
 
 2 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 
 
 
 
 o 
 
 
 
 
 
 I 
 
 I 
 
 I 
 
 I 
 
 I 
 
 80 
 
 I 
 
 I 
 
 I 
 
 
 
 
 
 O 
 
 
 
 o 
 
 o 
 
 
 
 O 
 
 
 
 
 
 I 
 
 I 
 
 I 
 
 9 
 
 O 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 o 
 
 
 
 o 
 
 
 
 
 
 
 
 
 
 O 
 
 Height of 
 
 28-26 
 
 2856 
 
 28-85 
 
 29-15 
 
 2 9'45 
 
 29 '75 
 
 30.05 
 
 30.35 
 
 30*64 
 
 30-93 
 
 
 Barometer. 
 
 ioobe,. 
 
 inchei. 
 
 inches. 
 
 
 
 
 inches. 
 
 Incfaei. 
 
 inchti. 
 
 inch*.. 
 
 
 
 
 
EXAMPLE 1. 
 
 What is the correction for refraction for an altitude of 8 5', the thermometer 
 standing at 50-0 and the barometer at 29-6 inches? 
 
 Answer (by inspection) 6' 25" : 
 
 and therefore, 
 
 Apparent altitude . . . . 8 5' 
 
 Refraction = 6 25" 
 
 True altitude 7 58 35 
 
 EXAMPLE II. 
 
 What is the correction for refraction for the same altitude, the thermometei 
 standing at 44 and the barometer at 29-45 inches? 
 
 ' // 
 
 Thermometer correction for altitude 8 5' = -\- () 6 
 Barometer ditto = 2 
 
 Correction for both is = -f- 4 
 
 Mean Refraction = 6 25 
 
 .-.True refraction = 621 
 
 o / // 
 
 Apparent Altitude =- 850 
 
 True refraction = C 27. 
 
 True altitude . . , < . . 1 8 ?0 
 
76 
 
 Table H. 
 
 Coefficients showing the per cent, of Refraction to be applied 
 to the Sun's Declination. 
 
 
 Hours from the Meridian, 
 
 
 Hours from the Meridian. 
 
 Lat. 
 
 1 H. 
 
 2 H. 
 
 3 H. 
 
 4 H. 
 
 5 H. 
 
 6 H. 
 
 Lat. 
 
 1 H. 
 
 2 H. 
 
 3 H. 
 
 4 H. 
 
 5 H. 
 
 6 H. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 IO 
 
 56 
 
 33 
 
 2 4 
 
 20 
 
 18 
 
 '7 
 
 36 
 
 94 
 
 82 
 
 7 1 
 
 64 
 
 60 
 
 59 
 
 12 
 
 63 
 
 39 
 
 28 
 
 2 4 
 
 22 
 
 21 
 
 38 
 
 95 
 
 85 
 
 74 
 
 6 7 
 
 63 
 
 62 
 
 H 
 
 69 
 
 45 
 
 33 
 
 27 
 
 25 
 
 2 4 
 
 40 
 
 95 
 
 87 
 
 77 
 
 70 
 
 65 
 
 64 
 
 16 
 
 74 
 
 5o 
 
 38 
 
 3 l 
 
 2 9 
 
 28 
 
 4 2 
 
 96 
 
 88 
 
 79 
 
 72 
 
 68 
 
 67 
 
 18 
 
 78 
 
 55 
 
 42 
 
 35 
 
 3 2 
 
 3 1 
 
 44 
 
 96 
 
 89 
 
 Si 
 
 74 
 
 7i 
 
 69 
 
 20 
 
 81 
 
 60 
 
 46 
 
 39 
 
 35 
 
 34 
 
 46 
 
 97 
 
 90 
 
 83 
 
 77 
 
 74 
 
 72 
 
 22 
 
 84 
 
 64 
 
 5 
 
 42 
 
 38 
 
 37 
 
 48 
 
 98 
 
 9 1 
 
 85 
 
 79 
 
 76 
 
 74 
 
 2 4 
 
 87 
 
 08J54 
 
 46 
 
 42 
 
 4 1 
 
 5 
 
 98 
 
 92 
 
 86 
 
 Si 
 
 78 
 
 76 
 
 26 
 
 89 
 
 70 
 
 57 
 
 49 
 
 45 
 
 44 
 
 52 
 
 98 
 
 93 
 
 88 
 
 83 
 
 Si 
 
 79 
 
 28 
 
 90 
 
 72 
 
 60 
 
 5i 
 
 48 
 
 47 
 
 54 
 
 99 
 
 94 
 
 90 
 
 85 
 
 83 
 
 81 
 
 3 
 
 9 1 
 
 74 
 
 63 
 
 54 
 
 5i 
 
 5o 
 
 56 
 
 99 
 
 95 
 
 9 1 
 
 87 
 
 85 
 
 83 
 
 32 
 
 92 
 
 77 
 
 66 
 
 57 
 
 54 
 
 53 
 
 58 
 
 99 
 
 96 
 
 92 
 
 ss 
 
 86 
 
 85 
 
 34 
 
 93 
 
 80 
 
 69 
 
 61 
 
 57 
 
 56 
 
 60 
 
 99 
 
 97 
 
 93 
 
 90 
 
 88 
 
 87 
 
 For the construction of the above table, see p. 67. 
 
77 
 
 Table 
 Inclination and Convergency of the Meridians. 
 
 Lat. 
 
 Inclina- 
 tion for 
 one mile. 
 
 Inclina- 
 tion for 
 six miles 
 
 fill 
 
 mi 
 
 8 2" 
 
 Lat. 
 
 Inclina- 
 tion for 
 one mile. 
 
 Inclina- 
 tion for 
 six miles 
 
 Convergencyl 
 for one 
 township of 1 
 36 miles. | 
 
 Lat. 
 
 Inclination 
 for one mile. 
 
 Inclina- 
 tion for 
 six miles 
 
 Conver^ency 
 for one 
 township of 
 36 miles. 
 
 
 
 10 
 
 II 
 9.18 
 
 ' // 
 
 55 
 
 LINKS. 
 I 3 .0 
 
 o 
 27 
 
 if 
 26.52 
 
 f It 
 239 
 
 LINKS. 
 36.9 
 
 o 
 
 44 
 
 ' It 
 50.19 
 
 ' // 
 501 
 
 LINKS. 
 70.1 
 
 II 
 
 10.13 
 
 I 01 
 
 14.2 
 
 28 
 
 27.66 
 
 2 46 
 
 3 8.6 
 
 45 
 
 52.00 
 
 5 I2 
 
 72.6 
 
 12 
 
 II.07 
 
 1 06 
 
 15-5 
 
 29 
 
 28.85 
 
 253 
 
 40.2 
 
 46 
 
 53.83 
 
 523 
 
 75.2 
 
 '3 
 
 I2.O2 
 
 I 12 
 
 16.8 
 
 3 
 
 3-3 
 
 300 
 
 41.9 
 
 47 
 
 55^7 
 
 534 
 
 77.8 
 
 H 
 
 12.98 
 
 i 18 
 
 iS.i 
 
 3* 
 
 31,26 
 
 307 
 
 43-6 
 
 48 
 
 57^7 
 
 546 
 
 80.6 
 
 i5 
 
 13.96 
 
 i 24 
 
 19.4 
 
 3 2 
 
 32.49 
 
 315 
 
 454 
 
 49 
 
 59^3 
 
 559 
 
 83.5 
 
 16 
 
 H-93 
 
 i 30 
 
 20.7 
 
 33 
 
 33-83 
 
 323 
 
 47.2 
 
 5 
 
 I O2.OO 
 
 6 12 
 
 86.5 
 
 '7 
 
 15.92 
 
 i 36 
 
 22.0 
 
 34 
 
 35- I 7 
 
 33 r 
 
 49.1 
 
 5* 
 
 I 04.17 
 
 6 25 
 
 897 
 
 18 
 
 16.91 
 
 141 
 
 2 3'4 
 
 35 
 
 36-50 
 
 339 
 
 59 
 
 52 
 
 I 06.67 
 
 6 40 
 
 93- 
 
 J 9 
 
 17-93 
 
 147 
 
 24.9 
 
 36 
 
 37-83 
 
 34 6 
 
 52.7 
 
 53 
 
 I 09.17 
 
 655 
 
 964 
 
 20 
 
 18.94 
 
 1 54 
 
 26.5 
 
 37 
 
 39-17 
 
 355 
 
 54-7 
 
 54 
 
 I 16.67 
 
 7 10 
 
 1 00.0 
 
 2J 
 
 19.98 
 
 2 OO 
 
 2 7 .8 
 
 38 
 
 40.67 
 
 404 
 
 56.8 
 
 55 
 
 1 H-33 
 
 7 26 
 
 103.7 
 
 22 
 
 21.02 
 
 2 06 
 
 2 9-3 
 
 39 
 
 42.17 
 
 4i3 
 
 58.8 
 
 56 
 
 i 17.17 
 
 743 
 
 107.6 
 
 23 
 
 22.10 
 
 213 
 
 30.8 
 
 40 
 
 43-67 
 
 4 22 
 
 60.9 
 
 57 
 
 I 20.00 
 
 8 oo 
 
 1 1 1.8 
 
 24 
 
 2 3- J 7 
 
 2 19 
 
 3 2 -3 
 
 4 1 
 
 45-i7 
 
 43 1 
 
 63.1 
 
 58 
 
 I 22.00 
 
 8 19 
 
 116.2 
 
 2 5 
 
 2 4 .30 
 
 2 26 
 
 33-8 
 
 4 2 
 
 46-85 
 
 441 
 
 65.4 
 
 59 
 
 I 26.66 
 
 840 
 
 120.9 
 
 26 
 
 25-38 
 
 232 
 
 35-4 
 
 43 
 
 48.52 
 
 45 1 
 
 67.7 
 
 60 
 
 I 30.00 
 
 9 oo 
 
 125.7 
 
 For the construction and use of the above table, see articles (13,) (14,) (15,) 
 (17.) (18,) page 70. 
 
 For details of instruction in U. S. Government Surveying, see Hawes' System 
 of "Rectangular Surveying," and Burt's "Key to Solar Compass." 
 
78 
 
 To Find the Meridian from " Polaris." 
 
 The north star, Polaris, being out of the pole of the equator, is in the meridian but 
 twice in a stellar day once above and once below the pole called the upper and 
 lower transits, or culminations. 
 
 It is also at its extreme distance, east and west, twice in a stellar day, called 
 greatest elongations, east or west. 
 
 At the time of a culmination, it would be only necessary to get the bearing of the 
 star to have the place of the true meridian. But this would require an exact knowl- 
 edge of the time, an element not usually possessed by surveyors. Moreover, the 
 observation must be made with certainty, at the instant, which is not always practi- 
 cable. On this account, this method is not in favor with surveyors. 
 
 At elongation, the apparent motion of the star is tangent to the vertical, and 
 therefore, for a few minutes, with regard to azimuth, it appears to stand still, thereby 
 Wording ample time for deliberate observation. 
 
 The distance of thrs star from the pole- called its polar distance, was 1 18' 16" 
 on January 1, 1885, and is diminishing at the rate of about 19.06" per year, whence 
 its distance in following years may be known.* 
 
 The azimuth of the star, corresponding to any polar distance, is variable with the 
 latitude. Thus, an observer at the equator would see this star say at eastern 
 elongation in the horizon, and at the distance of 1 18' 16" to the right of the pole, 
 or true meridian. 
 
 If now the observer should go north, the azimuth of the star would increase with 
 its altitude, till he should arrive at a latitude equal to the complement of the polar 
 distance, when it would be N. 90 E. Between these limits, the bearing of the st?,r, 
 at elongation from the pole, would vary according to the following equation, in which 
 Z = the azimuth, or bearing : 
 
 . 7 _ sin Polar Distance 
 : cosine Latitude 
 
 As the telescope of the surveyor's transit is not usually of sufficient power to show 
 the star in the daytime, the observation must be made at night, in which case the 
 cross-wires of the telescope must be illuminated by light reflected into the tube. A 
 piece of stiff white paper, with an opening large enough to admit of seeing the star 
 through it, and held obliquely in front of the telescope, will make a good reflector. 
 
 As generally but one of the elongations can be seen, on the same night, it is im- 
 portant to know, which one is observed. Also the latitude must be known, at least 
 approximately. 
 
 The pole is nearly in line between Polaris and the star Mizar, which is at the bend 
 in the handle of the Dipper, so that when these two stars are nearly in a horizontal line 
 
 and the dipper is ^jjj. j- of the pole, Polaris is at his greatest elongation ^J j- 
 
 In sighting to the star, the observer must be careful to keep his transit level 
 transversely, for the star is so high that inattention to this might introduce a serious 
 error into the resulting azimuth. 
 
 A satisfactory sight having been obtained, the telescope should be brought down 
 to fix a mark on the ground, at a distance of 300 to 400 yards from the transit. 
 
 This mark should be something clear and definite, like a nail set in a hub, driven 
 into the ground, which may be located by means of a plummet lamp, or by means 
 of a common lamp in a box, having a vertical slit in one side of say or f an inch in 
 thickness, with a plumb-line suspended from the slit, and manipulated by an 
 assistant. 
 
 The direction of the star being satisfactorily marked, compute the azimuth from 
 
 the above equation, and set the resulting angle off to the I 1 ?,. ] of the mark for 
 
 It may happen, that the resulting azimuth may have an odd number of seconds, 
 or fraction of a minute, not convenient to be set off with a vernier graduated to 
 
 * Small corrections to the distances thus calculated are needed, but do not amount to more than 30" IB 
 all ; see a Nautical Almanac. 
 
79 
 
 single minutes. In this case, find the distance carefully between the transit and the 
 mark, and multiply this distance by the tangent of the azimuth. The result set off 
 
 to the j* 1 ?? 1 * 1 } for ^ es t l e [ elongation, will point out the place of the true meridian. 
 
 left ( iv/i eastern 
 
 Meridian from Equal Altitudes of the Sun. 
 
 If the direction of a star were observed with a transit when it had a certain altitude 
 on the easterly side of the meridian and the direction again observed when it had an 
 equal altitude on the westerly side, then the bisector of the angle would give the direc- 
 tion of the meridian. 
 
 If these observations are made on the sun an allowance must be made for the slight 
 change in the sun's declination between the two observations. From about Decem- 
 ber 21 to about June 21 the sun is going north and from June 21 to December 21 it is 
 going south. The table given below shows the number of seconds the sun moves in 1 
 hour on different days in the year. 
 
 To an observer in north latitude, when the sun is going north, the mean of the two 
 vernier readings would lie to the west of south ; if the sun is going south the mean 
 would lie east of south. The correction to the mean of the vernier readings is found 
 
 by the formula ; : In this formula D is the total increase or decrease in 
 
 2 cos <p sin t. 
 
 the sun's declination between the two observations ; < = the latitude ; t = the hour 
 angle, or very nearly i the elapsed time. 
 
 Making the Observations. 
 
 1. In the forenoon, set up the transit, with the vernier set at 0. Point at some ob- 
 ject for an azimuth mark, preferably at the left of the sun, using the lower clamp and 
 tangent screw. 
 
 2. Loosen the upper clamp and point the telescope toward the sun and find the 
 sun's image in the field. Move the telescope slightly until the vertical and horizontal 
 wires are found. The beginner is cautioned against mistaking a stadia wire for the 
 middle wire. 
 
 In the forenoon the sun is rising and moving to the right. If the telescope has an 
 inverting eye-piece these motions will of course appear to be reversed. If a prism is 
 used the vertical motion will be contrary to what it would be without the prism, while 
 the horizontal motion will not be affected. 
 
 3. Set the telescope at an altitude a little above the sun. Set the vertical wire on the 
 left limb of the sun and follow it in azimuth, using the upper clamp and tangent screw, 
 until the lower limb of the sun just touches the horizontal wire. At this instant stop 
 following the motion in azimuth, note the time by a watch and then read the vernier. 
 It will be well also to read the altitude. 
 
 4. In the afternoon turn the telescope toward the sun, the altitude being the same as at 
 the. first observation. When it comes into the field set the vertical wire tangent to the 
 right limb of the sun. Follow it in azimuth until the lower edge of the sun again 
 touches the horizontal wire. Note the tune and read the vernier. 
 
 Calculations. 
 
 Take from the table the hourly change in declination for that day and multiply by 
 the number of hours and fraction of an hour between the observations. The result is 
 to be divided by twice the product of the cosine of the latitude by the sine of the hour 
 angle. This gives the correction to the mean of the vernier readings. The hour angle 
 is half the elapsed time and should be turned into degrees and minutes by multiplying 
 by 15. Take the mean of the vernier readings and then subtract the correction if the 
 sun is going north, add if it is going south. It is assumed that the circle reads from 
 to 360 in a clockwise direction. 
 
80 
 
 REMARKS. If the instrument is not in a very stable condition it will be best to 
 re-set on 0, point at the azimuth mark again, and then re-set at the proper altitude as 
 nearly as possible, before making the second observation. 
 
 The nearer the sun is to the east and west points the better the result. Observa- 
 tions near noon should be avoided. Observations at very low altitudes, say under 10 
 are unsatisfactory. 
 
 If only approximate results are desired the vertical wire may be made to bisect the 
 sun's disc in both cases. This would avoid the mistake of getting the wrong limb. 
 
 Date, April 10. 
 
 Forenoon observation 
 Afternoon " 
 
 EXAMPLE. 
 
 Latitude 43 N. 
 
 vernier A. Watch Reading. 
 
 , . 13 26' right of mark 7^. 18m. 
 
 " *' " 4h. 48m. 
 
 mean 
 
 148 13' 
 80 49' 30" 
 
 diff. 9k 30m. 
 
 Diff. lh. = 54" 
 64" X 9. 6 h. =513" 
 cos<= .7314 
 sin t= .9469 
 2 cos < sin t = 1.3851 
 513 
 
 t = 4h. 45m. 
 = 71 15 
 
 mean 80 49' 30" 
 corr 6' 10 
 
 1.3851 
 
 = 370."4=6' 10."4 
 
 Angle between ) fi ,, 
 
 meridian and mark f * 
 
 Hourly Motion of the Sun in Declination. 
 
 Month. 
 
 Jan. 
 
 Feb. 
 
 March. 
 
 April. 
 
 May. 
 
 June. 
 
 July. 
 
 Aug. 
 
 Sept. 
 
 Oct. 
 
 Nov. 
 
 Dec. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 tt 
 
 
 
 tt 
 
 tt 
 
 tt 
 
 I 
 
 + 12 
 
 43 
 
 57 
 
 58 
 
 45 
 
 21 
 
 IO 
 
 38 
 
 54 
 
 58 
 
 4 8 
 
 23 
 
 5 
 
 17 
 
 46 
 
 58 
 
 56 
 
 43 
 
 17 
 
 H 
 
 41 
 
 56 
 
 58 
 
 4 6 
 
 19 
 
 10 
 
 22 
 
 49 
 
 59 
 
 54 
 
 39 
 
 12 
 
 19 
 
 44 
 
 57 
 
 57 
 
 42 
 
 14 
 
 15 
 
 28 
 
 52 
 
 59 
 
 52 
 
 36 
 
 7 
 
 24 
 
 47 
 
 58 
 
 56 
 
 38 
 
 8 
 
 20 
 
 32 
 
 54 
 
 59 
 
 49 
 
 3i 
 
 + 2-J 
 
 28 
 
 49 
 
 58 
 
 54 
 
 34 
 
 -21 
 
 25 
 
 37 
 
 56 
 
 59 
 
 47 
 
 27 
 
 -4J 
 
 32 
 
 52 
 
 59 
 
 52 
 
 30 
 
 + 4J 
 
 30 
 
 4i 
 
 
 58 
 
 46 
 
 23 
 
 9 
 
 36 
 
 54 
 
 59 
 
 49 
 
 '5 
 
 IO 
 
81 
 
 Transit Solar Attachment. 
 
 For running Meridian or other lines by the Sun. 
 
 Written for tnis catalogue with special reference to the wants of Public Land Surveyors, for both common and 
 
 mineral lands, by J. B. DAVIS, Assistant Professor of Civil Engineering, 
 
 University of Michigan. 
 
 1. Remarks. The attachment herein referred to is the Davis and Berger 
 solar screen, prism, and colored shade glass, used for direct solar observation. 
 These inventions have been devised by the Mr. Berger, of the firm of C. L. Berger 
 & Sons, and by the writer. They are simply for the purpose of enabling one 
 to make an observation directly upon the sun's centre. This observation being 
 secured by readings of the horizontal and vertical circles, is reduced so as to 
 give the direction of the line of sight of the transit at the instant of the observa- 
 tion. Thus knowing the direction of the line of sight at a given instant it becomes 
 simply necessary to turn off the angle which this line of sight makes with the 
 meridian, to ascertain the position of the meridian. This angle is what is obtained 
 by reducing the observation, as above mentioned. A brief reference to the history 
 of these devices will best explain them. It occurred to the writer to see if an image 
 of the sun could be formed behind the eye-piece of a telescope at the same time 
 an image of the cross-wires was, and the latter image be made to quarter the 
 former, by allowing the sun to shine into the object end of the telescope and thence 
 directly through it. The experiment was made by holding a piece of white paper 
 behind the eye-piece, and adjusting the focus of the eye-piece and object glass. 
 The very first trial was readily successful. The next thing was to see if the posi- 
 tion of the instrument could be located by this means as near as the circles would 
 read. By the same simple means it was soon found that a motion given to the 
 telescope by either tangent screw might be so slight that the eye could not detect 
 it upon the circles, but evidence of it would be apparent in the position of the images 
 with reference to each other. This fact at once settled the question of whether 
 this would be a sufficiently delicate means of observation. It showed that the 
 observations would be closer than the circles would read. After some trials and 
 some months rest these facts were brought to the notice of others, and finally were 
 submitted to Mr. Berger for his opinion. He made a screen \vhich the writer 
 exhibited at the first annual convention of the association of Michigan Engineers 
 and Surveyors at Lansing. The matter was further studied by Mr. Berger. The 
 screen was much improved, and the mechanical construction of it brought to 
 the standard of the work done by this firm. Mr. Berger soon conceived the 
 idea of making the screen of ground white glass in a brass frame, as shown in 
 figs. 1 and 2,*so one might observe the position of the images directly upon it, 
 and thus secure not only the comfort of an easy position in observing, but the 
 consequent accompanying accuracy. The arm of attachment was perfected from 
 time to time. The screen of ground glass is mounted upon an arm that admits of 
 all adjustments of position, and is so attached to the side of the telescope tube that 
 it can be turned up out of the way when not needed. The reflecting prism 
 can be screwed on to the eye-piece cap for observing at high altitudes. This also is 
 adjustable so as to look in any desired direction from the telescope tube. The 
 diagonal eye-piece also has its movable colored shade glass as above stated. With 
 these attachments observations on the sun at all altitudes may be made in two 
 ways. By looking directly at it through the simple colored glass for low altitudes, 
 or through the prism and its shade glass for high altitudes. The other way is to 
 receive on the screen the images of the cross-wires and the sun and make the image 
 of the cross-wires just quarter the image of the sun by means of the slow motion 
 screws to the circles of the instrument. For this method the colored shade glasses 
 are not to be used. With this complete outfit one may work whichever way seems 
 bwst. 
 
 * For Figures 1, 2, 3, 4, 5, 6 and 7 see page 175. 
 
82 
 
 These devices are being more and more perfected, and will be protected by letters 
 patent, and Messrs. C. L. Berger & Sons make and sell them exclusively. 
 
 2. Rem irks. Certain precautions are necessary in the use of this method 
 of finding the true direction of a line as well as in any other. It is not wise to 
 observe the sun, read the circles, note clown the readings and leave the instrument 
 standing there while making the reductions. It will get out of place in some way, 
 very likely. Therefore, as soon as the observation is completed and the readings 
 of the circles noted, set the line of sight on some fixed point and read the plate 
 again, noting this reading. Of course the two plate readings will give the horizon- 
 tal angle from the sun to the line. This will enable the observer, after finding the 
 direction of the line of sight when set on the sun, to readily ascertain its direction 
 as set on the fixed point referred to, thus determining the direction of the line from 
 the point over which the instrument is set to the fixed point. This line may be 
 chosen before beginning the observation, and become the reference line for the 
 work in hand. 
 
 3. Remarks. For the purposes of reduction the process by equations is 
 used instead of one by rules. The introduction of symbols and signs is a much 
 simpler matter than many suppose. It is nothing but this. We agree that a char- 
 acter of some sort or other shall represent a certain thing and nothing else. 
 Whenever this character occurs, therefore, it simply means the thing we have set 
 it for. That is all there is of symbolical representation. These very words here 
 printed are all symbols. The method is universal. We here, as elsewhere in 
 algebraic processes, make a special application of it. The rules for a case of this 
 kind would be very cumbersome and give the user far more trouble than will be 
 necessary for mastering the few equations given below. The record of the pro- 
 cesses is hereby reduced to a few lines, and one has not to go searching through s 
 page for a point here and there, but places his eye at once upon what he wants, 
 where all will be found in a compact form. Of course one needs to read each word 
 and each sign. Nothing must be slurred over or missed. The record as set forth 
 below is exact, complete and reliable. 
 
 4. Remarks. All computations should be thoroughly checked, and check 
 equations and devices are given. These should always be applied, without fail, as 
 no one can implicitly trust a computation by a single process, unrepeated, even if 
 simple. No one sljould who is a surveyor or engineer. Several checks are given. 
 One used is sufficient, usually. If one distrusts the check because it shows th 
 work to be wrong, it may be of some satisfaction to use another or more than one. 
 
 5. Remarks. The directions prepared below are intended for use, word by 
 word, and step by step. It is hoped that they will prove in convenient form for 
 use as a chart to direct the efforts of the observer in his first use of these attach- 
 ments and this method. Therefore, it is thought that one may safely do as told, 
 trusting the next step to the next statement. They have been prepared with this 
 view. 
 
 6. Using the Screen. 
 
 a. Directions. Set the instrument so the sun can shine in at the object end 
 of the telescope, and directly through it. Run put the eye-piece and adjust the 
 screen behind it, by its sliding arm, so that a distinct image of the cross-wires can 
 be seen on the screen within the lighted spot made by the shining sun, as shown 
 in fig. 2. Set the object glass so as to clearly define the image of the sun on the 
 screen. Repeat these trials, and adjust the parts of the telescope and screen so 
 that the clearest image of both the cross-wires and the sun will be obtained that 
 the telescope will give. Mark the slide on the arm of the screen and the eye-piece, 
 so they can be easily set thereafter for an observation. 
 
 b. Remarks. The eye-piece, when all is in exact position, will be found to 
 be considerably farther out than for an ordinary sight. The marking of the sliding 
 arm and eye-piece will save time in ths future. These trials, when made with a 
 new apparatus, should be conducted at leisure and with extra care, for the purpose 
 of fitting the apparatus carefully to the telescope. A few trials may be needed at 
 first in order to accustom the observer to recognize the best definition of the images. 
 
 This solar screen is especially adapted to the ordinary surveyors' and engineers' 
 transit telescopes, with erecting eye-pieces. It is not adapted to be used with invert- 
 
83 
 
 Ing or astronomical telescopes, unless during an observation the aperture of the 
 objective is cut down to inch diameter, by means of a diaphragm placed in front of 
 it, when the image can be seen as sharply defined as those of the erecting telescope; 
 or the observations must be made with the shade glasses and reflecting prism alone. 
 
 7. Using the Colored Shade Glass. 
 
 a. Directions. Attach the colored glass shown in fig. 4, to the eye-piece, 
 to shield the eye from the sun and look directly at it, setting the cross-wires so as 
 to quarter it. 
 
 b. Remarks. This will be found entirely satisfactory when the sun's alti- 
 tude is so low as to enable the observer to bring his eye in apposition with the eye- 
 piece of the telescope with ease. 
 
 8. Using- the Diagonal Eye-piece. 
 
 a. Directions. Screw on the prism, as shown in fig. 3, to the end of the 
 common eye-piece. Look directly through the shade-glass, if observing in that 
 way, turning the prism either way so as to make it convenient to look into it. If 
 any trouble is experienced in finding the sun with it. let the sun first shine through 
 the telescope, the colored shade-glass being turned aside, till the brilliant light 
 perceived in the aperture of this eye-piece shows the telescope to be rightly 
 directed. Cover the aperture with its shade-glass and proceed. 
 
 b. Remarks. By attaching the reflecting prism to the eye-piece of the tele- 
 scope, the light is reflected at right angles to the the line of sight of the telescope, 
 and it thus becomes what is termed a diagonal eye-piece. 
 
 This prism can be used for direct observation when the altitude of the sun is 
 too great to allow the eye to be applied directly to the eye-piece of the telescope, 
 and not so ^reat as to bring the eye-piece too far over the plate, but through this 
 range of altitudes the solar screen can be used without the prism, as shown in lig. 2, 
 and it will usually be found advantageous to do so. 
 
 Since the prism in effect withdraws the eye about half an inch further from the 
 eye-piece of the telescope than its natural position, that being about the distance 
 traversed by the light in passing through the prism, the high magnifying power 
 used in C. L. Berger & Sons' transit telescopes makes the use of the reflecting 
 prism for direct observation a little awkward, and it will usually be found more 
 satisfactory when using the prism to use the solar screen with it. 
 
 9. Using the Reflecting Prism and Solar Screen combined. 
 
 a. Directions. Attach the prism, and direct the telescope as in 8. Then, 
 leaving the aperture of the prism uncovered, adjust the solar screen so as to receive 
 the images of the sun and the cross-wires, as shown in fig. 1. 
 
 b. Remarks. For observing the sun at high altitudes it will be found that in 
 this, otherwise most difficult of all positions, the use of the solar screen combined 
 with the prism will enable the engineer to make his observation with the greatest 
 ease and precision. 
 
 10. Making the Observations. 
 
 a. Directions. Direct the telescope to the sun, and by means of the slow 
 motion screws, cause the image of the cross-wires to exactly quarter the sun's image. 
 Read both circles and record the readings. Eefer the position of the instrument to 
 some fixed line, and once, after the above work, by another plate reading. Also 
 note and record the exact instant of time of the observation by the watch. 
 
 b. Remarks. This observation with the watch may be used as hereafter 
 indicated to simplify and lessen the amount of work in making the reductions. A 
 fair watch of ordinary accuracy is sufficient. The entire work can be carried on 
 without a watch at all, but it takes some more figuring. 
 
 11. Use of the Nautical Almanac. 
 
 a. Remarks. In order to use the observations, made as above directed, it 
 is necessary to find the sun's apparent declination for the time of observation. 
 This is done as directed below. 
 
 b. Conditions. Let all the algebraic signs be carefully observed throughout 
 the work. Use the watch time. 
 
84 
 
 c. Directions. For finding the Sun's apparent declination. Look in the table 
 of Washington Solar Ephemeris against the date of the observation, and take out 
 the following quantities. First, the sun's apparent declination, with its sign, -j- 
 when N., when S., from its column. Second, the hourly change, with its sign, 
 from its column. Find from a map or otherwise, the difference in longitude 
 between the place of observation and Washington, as near as one-half hour, or 
 seven and one-half degrees. This is -f- when W. and when E. of Washington. 
 Add to this difference of longitude the time of the observation from noon, this time 
 being -j- when the sun is W. and when E. of the meridian. Multiply the hourly 
 change by this result, in hours^ noting all the signs. Apply this product, regarding 
 its sign, to the sun's apparent declination as taken, from the table, for the sun's 
 apparent declination at the time of the observation. 
 
 d. Example. Date, 1881 6 14. Hour, 9h 26m 24*, A.M. Longitude 
 about 40 minutes East of Washington, considered in time. 
 
 O's apparent declination, 1881 6 14. 
 Washington mean noon, -f 23 18' 15" 
 Hourly motion, 1" 
 
 Time of observation from noon, 2 hours 30 minutes, about. 
 
 Longitude East of Washington, 40 minutes. 
 
 Total time of correction, 3 hours 10 minutes, = 3 l /e hours. 
 
 Amount of correction = 3 l /6 X 1" = 22 ^" 
 
 O's apparent declination from table, -f- 23 18' . 15// 
 
 O's apparent declination at time of observation, + 23 17' 53" nearly, 
 
 12. Reducing Observations. 
 
 a. Conditions. Let h' = the sun's altitude, as observed. 
 
 Let = the latitude of the place of observation. 
 Let 6 = the sun's apparent declination at the time of obser- 
 vation, found as above directed. 
 
 Let z'= the sun's observed zenith distance. 
 Let z = the sun's true zenith distance, always -f. 
 Let k and A/ be two auxiliary angles used in the reductions. 
 Let A = the azimuth of the line of sight of the instrument at the instant of the 
 observation, reckoned from the N. point of the horizon, either E. or W. as the sun 
 is E. or W. of the meridian. 
 
 Let t = the sun's apparent hour angle at the time of the observation, that is the 
 local apparent time from apparent noon plus the change in the sun's right ascension 
 between apparent noon and the time of the observation. This is -{- when W. and 
 when E. of the meridian, or -j- for P.M , and for A.M. times. The mean or 
 watch time is sufficient for use in 2. 
 
 Let p = an auxiliary angle used in some of the reductions. 
 Let all signs be faithfully regarded. Let logarithms be used. 
 
 b. Directions. For finding z from z' . Use the following equations. 
 
 *'=90 /?' (1) 
 
 z = z' + 55" tan z' (2) 
 
 C. Directions. For finding A when 0, 6 and z are given. 
 
 Find tan ^ (k fc') = cot ^ O~H) tan ^ O <T> cot ^ z . (3) 
 
 When ^<<J and of the same name find k = y 2 z -}- % ( k ~ *0 ' ( 4 ) 
 
 When ^>d and of the same name find k'=y 2 z~y 2 (k A;') . . (5) 
 
 When <p and 6 have different names find k f =*4 z }4 (k A/) . . (6) 
 
 Then find A from Cos A = tan k tan ^> or tan V tan <j> . . . . (7) 
 
 Checks. 
 
 When (4) is used L*= (8) 
 
85 
 
 ....... (10) 
 
 Sin Sin 
 
 Find Sin p = sin A cos ...... (12) 
 
 Sin p and cos p are at the same place in the table. 
 d. Example. <j> = 42 16' 30" N. * = 52 43' 30" 
 
 6 = 18 13' 20" N. z = 2G 21' 45" 
 
 Checks* 
 
 (5 = 24 3' 10" 
 H)=3014'55" 
 
 d)=12 1'35" 
 
 = 0.2342195 Tan <fr = 9.9586273. Sin = 9.8278148 Cos 6 = 9.8691875 
 rf) = 9.3284570 Tan fr= 9.2477939. Cos A;' =9. 9933068 Sin 1=9.9943079 
 Cot y 2 z =0.3048785 Cos A= 9.2064212. Cos ;> = 8345080 Sin = 9~8634954 
 Tan %(* jf)= 9.8675550 3894. < - , - 
 
 346 318. At same place in table. 
 
 204 A = 9915'22"5 
 
 % (k k'} = 36 23' 45'' Sin = 9.8278148 Cos V = 9.9933061* 
 
 y 2 z =26 21 45" Sin 6 = 9.4951325 Cos k =9.660623'2 
 
 ~ 
 
 e. Remarks. Look out tan 0, cos 0, and sin 0, at one search. Use either check 
 as may be preferred. This operation need not be performed oftener than the 
 aemands of the work require, the plate being used mean time. 
 
 13. Remarks. 
 
 The observations and reductions can be always made, according to the process 
 given, without a watch, but the latitude of the place must be known. It must bo 
 carried on a9 the survey proceeds, by measurement, or an observation made to 
 determine it with the instrument. If it becomes necessary to find the latitude ill 
 may be done as follows : 
 
 14. Finding the Latitude by the Sun. 
 
 a. Directions. For Observations. Near noon begin to observe the sun 
 a little before it reaches its greatest altitude. By means of the slow-motion 
 screws keep the sun's image exactly in place on the screen, or by direct sight keep 
 the cross-wires exactly on the sun. As it moves upward just carefully follow it, 
 recollecting that the object is to get its greatest altitude. Be careful to stop fol- 
 lowing it when it turns and begins to descend. 
 
 b. Directions. For Reductions. Find z, as in 12, b. Find the sun's appar- 
 ent declination, <5, as in 11, c. Then 
 
 z + & = <, the required latitude ..... (13) 
 Be sure to observe the Algebraic signs, as 6 may be -f or . 
 
 c. Remarks. Having the latitude in this way, the observations and reduc- 
 tions may be conducted according to the processes above given. The latitude once 
 caref ulty ascertained by this or some other method, may be preserved by the dis- 
 tance traversed north or south of the point of the last observation for latitude. It 
 will at once appear that the measurement and observation may be made to check 
 each other. The method of reducing the change in latitude by linear measurement 
 may be as follows: 
 
 15. Finding: the Latitude by Linear Measurement. 
 
 a. Conditions. The latitude of the point measured from, or reckoned from, 
 must be known. The measurements must be reduced to the north and south 
 direction from the reference point. Let reduced distances north be -fv and those 
 south be . Let all signs be observed. Let the true bearings, or directions of all 
 lines with the meridian of the reference point, be given. Let any number of courses 
 be run in any direction. 
 
6. Directions. For reducing the north or south distances. Multiply the 
 length of each course by the cosine of its bearing, the results being given signs 
 as above indicated, -f- for northerly courses, and for southerly courses. Sum 
 these results regarding the signs. 
 
 c. Remarks. This sum will be the distance north or south of the reference 
 point. 
 
 d. Directions. For reducing feet to minutes of Latitude. Find the length of 
 a minute of latitude for the place by this equation. 
 
 m = 6076.36 
 
 Then divide the traversed distance north or south of the reference point by the 
 value of m found from this equation. 
 
 e. Remarks. The result will be the minutes and decimals of a minute o^ 
 the new point from the reference point. This value of m will be in feet, hence the 
 north or south distance must be in feet. 
 
 16. Remarks. The latitude may be dispensed with during a day's work 
 after the first satisfactory observation. It may be for a longer period if the watch 
 is to oe depended upon. It will be well to find the latitude, and check the work 
 occasionally, where the watch is used. In order to prepare the watch for this work, 
 proceed as follows : 
 
 17. Correcting the Watch. 
 
 a. Directions. For correcting the Watch by a Noon Observation. Having 
 ascertained the bearing of a line without the aid of the watch, as at first directed, 
 near noon set the line of sight in a meridian. Set the telescope so the sun can be 
 seen in it, or received on the screen as it passes the meridian. Note the time by 
 the watch when the sun's west side comes in apparent contact with the vertical 
 cross-wire. Note the watch time when the east side of the sun just touches the 
 vertical wire. Find the time halfway between these two noted times for the time 
 of the meridian passage of the sun's center, or the time of apparant noon, by the 
 watch. 
 
 b. Remarks. The time as above found should differ from exact noon by 
 just the equation of time for that date and time as given in the Nautical Almanac. 
 Observe the sign there attached to the equation of time. The watch may then be 
 set to true time if not correct. That is, it may be set so that the time of the sun's 
 meridian passage will be just the equation of time, with its sign, from exact noon. 
 
 c. Remarks. The watch may also be corrected directly from an observation, 
 reduced as at first directed in 1C and 12. Here it will be necessary to take the 
 watch time of the observation, as directed in 1C. Having done so, and reduced the 
 observation by 12, proceed as follows : 
 
 d. Directions. For correcting the Watch by an observation at any time. Hav- 
 ing found A and 2, and knowing <5, find t by the following equation. 
 
 sin A sin z 
 
 Sm * = C08 d < 10 > 
 
 This being in arc. reduce it to time at the rate of four minutes of time to one 
 degree of arc. 
 
 e. Remarks. This result should differ from the watch time of the observation 
 from mean noon, by just the equation of time, with its sign. If it does not, set the 
 watch so it would have done so had the observation been made with the corrected 
 watch. 
 
 18. Remarks. Having corrected the watch by the last method, the value of 
 t in time may be found from the value of t at this observation by noting the time 
 by the watch of another observation, and thence finding the elapsed time. This 
 applied to the first value of t will give its value for the last observation. Thus the 
 value of t may be carried forward as long as the watch runs true. Of course it will 
 occur to many at once that the watch can just as well be used to measure the 
 elapsed time without being corrected. This is too careless. The better way is to 
 keep a careful oversight of the watch by correction. Thereby it may be known 
 how much the watch is to be trusted. It is always best to establish a routine sy 
 tern in these matters, as soon as practicable, and adhere faithfully to it. 
 
87 
 
 19. Remarks. When the watch is corrected by either method, it will give 
 -ne value of t in time directly as follows : Note the time of an observation. Apply 
 to this time the equation of time with Us sign, as given in the Solar Ephemeris Table 
 of the Nautical Almanac. The result will give the apparent time of the observation 
 from apparent noon, -f- when the sun is west of the meridian, and when it is east 
 This found is the required value of t. 
 
 2O- Reducing Observations. 
 
 Conditions. Let the notation be as before. 
 
 Let t = the sun's apparent hour angle at the time of the observation, that is the 
 local apparent time from apparent noon This is -f- when W. and when E. of the 
 meridian, or -f for P.M., and for A.M. times. 
 
 Let the value of ( be found by 18 or 19, and reduced to arc at the rate of one 
 degree of arc to each four minutes of time, the work being carried out to seconds 
 of arc. 
 
 o. Directions. For finding A when 6. , and z are given. Find A from the 
 following equations. 
 
 .^... ~ sin t 
 Check - c^ = ^In-A 
 
 c. Example. <J = 18 30' 20" N. z = 52 43' 30" t = 55 46' 32"5 
 Cos 6 = 9.9776554 ] 
 Sin t= 9.91 74225 h 
 
 -8950779 | Check. 
 
 Sin z = 9.9007700 J f 
 Sin A = 9. 9943079 J 
 
 20. Remarks. The value of A as determined in these examples is greater 
 than 90, because the sun is south of the zenith. The value of t used in the second 
 example was found from the first, hence the exact check. It may be noticed how 
 much less figuring is required in the second example than in the first. It should 
 be noted, however, that more than one check is figured out in the first example, 
 and so more than the necessary figures shown. The value of A is carried out with 
 exactness in order that the process may be fully illustrated. 
 
 21. Summary. Several courses are hereby opened to the surveyor. This 
 is done that he may have the more checks at his command, and so make certain of 
 his work, It may be well to indicate these courses in a catalogued lorm for easy 
 reference. The courses are 
 
 The processes of ID, 12, and 14 or 15. 
 
 The processes of 1C, 12, and 14 or 15, and thence 
 
 16, a, or 16, d, and 18 or 19 and 2O. 
 
 22. Cautionary. Keep the levels and the vernier of the vertical circle in 
 good adjustment. Also keep the adjustment of the axes of the instrument, the 
 transit axis and the vertical axis, in good order. 
 
 23. General Remarks. It will be seen that in doing solar work with these 
 attachments in the manner explained above, the observation of the sun depends on 
 the ordinary line of sight of the telescope exactly as in all Geodesic work. 
 
 For this reason no extra adjustments are required. The accuracy of the observa- 
 tion in no way depends on these attachments, which are merely conveniences to 
 enable one to make solar observations with the ease and precision of ordinary 
 terrestrial work. 
 
 Other Solar Attachments are mechanical devices requiring special adjustments, 
 and considerable care is necessary to keep these adjustments perfect, while they 
 cause some degree of anxiety and doubt in the mind of the engineer as to whether 
 they are quite perfect or not. 
 
 With this invention all these sources of anxiety are avoided, the solar observation 
 being made with the telescope of the transit itself, while it has the advantage of 
 being applicable to every surveyors' and engineers' transit, is so light as not to add 
 appreciably to the weight of the instrument, so simple as to require no special pro- 
 vision for its care, and so cheap as to be within the reach of every surveyor. 
 
88 
 
 On Stadia Measurement. 
 
 Written especially for this Catalogue by GBO. J. SP*CHT, C. E., San Francisco, Cal. 
 
 A transit or theodolite, which is provided with the so-called stadia wires and a 
 Tcrtical circle, furnishes the means to obtain simultaneously the distance and the 
 height of a point sighted at without direct measurement, and with the only use of 
 a self-reading rod, held at the point of which the horizontal and vertical position 
 is to be determined in reference to the instrument-point. 
 
 Besides the ordinary horizontal and vertical cross hairs of the diaphragm of the 
 telescope, two extra horizontal hairs are placed parallel with the center one, and 
 equally distant on each side of it, which, if the telescope is sighted at a leveling 
 rod. will inclose a part of this rod or stadia-rod, proportional to the distance from 
 the instrument to the rod. By this arrangement we have obtained an angle of 
 sight, which remains always constant. 
 
 Supposing the eye to be in the point O (Fig. 1) , 
 ^ the lines O e and O k represent the lines of sight 
 Fig.lt ^S\ from the eye through the stadia-wires to the rod, 
 
 which stands consecutively at k e, i d. h c, g b and 
 / a. According to a simple geometrical theorem 
 we have the following proportion : 
 
 Oa:Ob:Oc:Od:Oe=af:bg:ch:di:ek, 
 
 which means that the reading of the rod placed 
 on the different points a, 6, c, d and e is propor- 
 * tf tional to the distances O a, O 6, O c, O d and O e. 
 
 The system of lenses which constitute the telescope do not allow the use of this 
 proportion directly in stadia measurements, because distances must be counted 
 from a point in front of the object glass at a distance equal to the focal length of 
 that lens. 
 
 _f 
 2 
 
 Figure 2 shows a section of a telescope provided with stadia wires. 
 In order to determine the distance of the rod from the instrument it will be neces- 
 sary to use the following equations. From the "law of lenses" we have the relation 
 
 1 1 1. 
 
 in which /, and / 2 are "conjugate foci " and /is the focal length of the object glass. 
 From the diagram it is evident that C : A B = D : ab. If we let p = the dis- 
 tance of the stadia wires from each other, /,= distance C and a = the space on the 
 rod AB, and D the distance from the center of the instrument to the rod, then the 
 second equation becomes / 2 : a = /, : p. Eliminating/! from these equation we find : 
 
 or we may write, since -= is constant, 
 
 = a k 4- f : 
 
From the center of the instrument to the rod the distance is 
 
 c being the distance from the objective to the center of the instrument. 
 
 Since (c -f/) is practically a constant it is usually denoted by the single letter c 
 and is known as the " constant of the instrument." 
 
 When the line of sight is not level, but the stadia held at right angle to it, the 
 formula for the horizontal distance is : 
 (2) D = fc.a.cos n ~\- c -j- om. 
 
 The member om 
 
 -- sin n ; for a = 24', n 
 
 45 the value of om is but 8.4', and for 
 
 o = 10' , n = 10 it is 0.86' ; this shows that om in most cases may safely be omitted. 
 
 Some engineers let the rodman hold the staff perpendicularly to the line of sight ; 
 they accomplish this by different devices, as, a telescope or a pair of sights attached 
 at right angle to the staff. This method is not practicable, as it is very difficult, 
 especially in long distances, and with greater vertical angles for the rodman to see 
 the exact position of the telescopes, and furthermore, in some instances it is entirely 
 Impossible, when, for instance, the point to be ascertained is on a place where only 
 the staff can stand, but where there is no room for the man. The only correct way 
 to hold the staff is vertically. 
 
 In this case we have the following : (Fig. 4) 
 
 MF = c + GF = c + &.C.D. 
 CD must be expressed by AB. 
 AB = a. AGB = 2m. 
 CD = 2GF tan.m. 
 
 And finally, after many transformations : 
 
 D=c.cos n-f-a.A;.cos 2 n a.fc.sin 2 n tan j rn. 
 
 The third member of this equation may safely be neglected, as it is very small 
 even for long distances and large angles of elevation (for 1500', n = 45 and k= 100, 
 it is but 0.02'). Therefore, the final formula for distances, with a stadia kept ver- 
 tically, and with wires equi-distant from the center wire, is the following : 
 (3) D = C.POS n-\-a.k.cos*n. 
 
 The value of c.cos n is usually neglected, as it amounts to but 1 or 1.5 feet ; it is 
 exact enough to add always 1.25' to the distance as derived from the formula 
 (3a) D = a.&.eos'n 
 
 without considering the different values of the angle n. 
 
 In order to make the subtraction of the readings of the upper and lower wire 
 quickly, place one of the latter on the division of a whole foot and count the parts 
 
90 
 
 included between this and the other wire ; this multiply mentally by 100 (the con- 
 stant &) which gives the direct distance D'. 
 
 In cases where it is not possible to read with both stadia wires, it is the custom 
 to use but one of them in connection with the center wire, and then to double the 
 reading thus obtained. "With very large vertical angles, this custom is not advis- 
 able, as the error may amount to 0.50 % . 
 
 Fig,4, 
 
 j. 
 
 To find the height of the point where the stadia stands above that one of the 
 Instrument, simultaneously with the distance, we have the following : 
 
 We assume in reference to figure 4, 
 
 9 = height of instrument point above datum. 
 
 MP= D = horizontal distance as derived from formula (3). 
 
 n = vertical angle. 
 
 h = FE = stadia reading of the center wire. 
 
 Q = height of stadia point above datum ; it is 
 
 Q = q -f D tan n h. 
 
 The substraction of h can be made directly by the instrument, by sighting with 
 the center wire to that point of the rod, which is equal to the height of the telescope 
 above the ground (which is in most cases =4.5") ; q will be constant for one and 
 the same instrument point ; then the formula : 
 
 Q = D tan n ; 
 this in connection with formula (3) gives 
 
 Q = c sin n -f- & cos n. sin n. 
 
 or Q = csinn a. 
 
 The first term of the equation can be neglected, when the vertical angle is not too 
 large ; hence the final formula for the height is 
 
 (5; Q_a.fc. 8in2n 
 
 2 
 
 The position of the stadia must be strictly vertical. 
 
 The error increases with the height of m; (m = height of center wire on the 
 rod). In shorter distances the result is seven-fold better when the center wire is 
 placed as low as one foot than it is at 10' ; in longer distances this advantage is 
 only double. 
 
 It is always better to place the center wire as low as possible. If the stadia is 
 provided with a good circular level, the rodman ought to be able to hold it vertically 
 
91 
 
 within 600"; that means, that the inclination of the stadia shall not be more than 
 0.0-23' in a 10' stadia, or 0.034' In a stadia of 15' length. 
 
 Determination of the two constant coefficients c and k. Although the stadia wires 
 are usually arranged so that the reading of one foot signifies a distance of ,100 feet, 
 I will explain here, how to determine the value of it for any case. Suppose the 
 engineer goes to work without knowing his constant, and not having adjustable 
 stadia wires. The operation then is as follows : 
 
 Measure off on a level ground a straight line of about 1000' length; mark every 
 100', place the instrument above the starting point, and let the rodman place his 
 rod on each of the points measured off; note the reading of all three wires separ- 
 ately, repeat this operation four times ; the telescope must be as level as the ground 
 allows ; measure the exact height of the instrument, i. e ., the height of the telescope 
 axis above the ground. Th^n find the difference between upper (o) and middle 
 (m) wire; between middle (w) and lower (M) wire, and between upper (o) and 
 lower (?*) wire, from the four different values for each difference, determine the 
 average value; then solve the equation for the horizontal distance (1) D = fc.a-f-c., 
 with the different average values, and you find the value of k and c. In case the 
 stadia wires should not be equi-distant from the center wire, there will be three 
 different constants, one for the use of the upper and middle, one for the use of the 
 middle and lower, and one for the upper and lower wire. 
 
 If the stadia wires are adjustable, the engineer has it in his power to adjust them 
 so that the constant k = 100, or k = 200, which he accomplishes by actual trial along 
 a carefully measured straight and level line. 
 
 The constant c, which is usually one and a half times the focal length of the object- 
 glass, can be found closely enough for this purpose by focussing the telescope for a sight 
 of average distance, and then measuring from the outside of the object-glass to the 
 capstan-head screws of the cross-hairs. This constant must be added to every stadia 
 sight; it may be neglected for longer distances. 
 
 Stadia Measurements. 
 
 Written for this catalogue and manual by H. C. PEARSONS, C. E., Fenysburg, Mich. 
 
 In view of the great and growing interest in the subject of " Stadia Measurements,*' 
 the following solution of the problem is offered, as applied to inclined measurements. 
 
 This solution is made from a different geometrical consideration than that usually 
 employed, and it effectually does away with the necessity for any subsequent cor- 
 rections, as with most schemes in use for inclined distances. 
 
 In the following discussion, let 
 
 R =the reading of the stadia rod; 
 
 D = the horizontal distance from plumb line of transit to stadia rod, which must 
 
 be vertical. 
 
 m = the angle of elevation or depression to the smaller reading of the stadia rod. 
 n = the same angle to the larger reading. 
 
 Through the point c, at the distance of unity from the centre of Instrument, 
 dra^v the vertical cb. Then the rod AB, being also vertical, the triangles a ob 
 and A o B are similar, as are also the triangles cob and C o B. But the read- 
 
92 
 
 Jug, R, of the rod AB is the difference of the tangents of the angles of elevation, 
 m and n. Also, the distance a & is the difference of the tangents of these angles, 
 m and n, to distance unity, as given in the trigonometrical tables. 
 
 Whence, to find the horizontal o C = D, we have simply to divide the reading of 
 the " Stadia Hod" by the difference of the tangents of the angles of elevation. Or, by 
 formula, 
 
 p^ B 
 
 Tan. n Tan. m 
 
 If one of the angles should be a depression or , we must then divide by the aunt 
 of the tangents, and the formula would be 
 
 D 
 
 Tan. n -f- Tan. m 
 
 Example. It n= 12 16', nat. Tan = .217426 
 
 "m=1010', " " = .179328 
 
 The difference of the tangents = .038098 
 
 Then, if R = 12.26 feet, 
 
 It may happen that our transit has no vertical circle, or that we have no trigono- 
 metrical tables at hand. In either case, introduce an auxiliary rod, c b between the 
 stadia rod and the plumb-time of transit, and at some known horizontal distance, 
 preferably 100 feet, from the latter, and note the intercept a 6. 
 
 This intercept is the analogue of the difference of tangents used in the former 
 case, and must be used in the same manner, in dividing the reading of the stadia rod, 
 when we bhall nave the distance, D, in terms of the distance of the auxiliary rod from 
 the transit. 
 
 Example. Suppose the intercept a 6 on the auxiliary rod, at distance 100 feet, 13 
 .845 foot, and that the reading R, of the stadia rod is 12 feet, then 
 
 oC = D = (12 -f- .845) X 100 = 1420 feet. 
 
 If the height, H, of the foot of the stadia rod, above or below the height of 
 Instrument, be wanted, it may be had from the following equation : 
 
 II = -|- D Tan. m, 
 
 in which the + sign must be used for angles of elevation, and the sign for those 
 of depression. 
 
 Or if the auxiliary rod be used instead of the vertical arc, note the intercept a b 
 on this rod, between the level line oC and the line of sight to the foot of the stadia 
 rod, and 
 
 Multiply this intercept by the ratio ofDto oc. 
 
 Example in the last case, If ca = 1.06 ft, oc being 100 feet, and D = 1420 ft. 
 then 
 
 CA = H = ca - 1.06 = 16.05 feet. 
 
The Adjustments of the Auxiliary Telescopes of Mining 
 
 Transits. 
 
 The Detachable Side-Telescope. 
 
 This telescope, illustrated on page 189, as ordinarily made, is attached to the 
 transverse axis of the mam telescope by means of a hub, which is screwed upon a pro- 
 longation of this axis beyond the .standards. The hub contains an independent hori- 
 zontal axis upon which the side-telescope may be revolved, and to which it may be 
 clamped. The side-telescope is usually set parallel to the main telescope, and look- 
 ing in the same direction, but it may be set so that it is inclined at a given verti< al 
 angle when the main telescope is horizontal. A counterpoise is attached to the other 
 end of the transverse axis of the main telescope, so as to balance the weight of the 
 side-telescope and retain that axis horizontal when the side-telescope is in use. The 
 side-telescope is mainly intended as an auxiliary in measuring vertical angles, and it 
 is on this account that the simple means of attaching it to the transit, here described, 
 has been adopted by us as sufficient for the purpose, although it will be very diffi- 
 cult to place its line of collimation truly parallel to the main telescope for all focus- 
 sing positions of the object-slide. 
 
 The adjustments of the detachable side-telescope are as follows : 
 
 1. To place its vertical wire perpendicular to the transverse axis of the instru- 
 ment. Attach the side-telescope and the counterpoise to the transverse axis. 
 Clamp the side-telescope slightly to its hub, bisect a point by its vertical wire and 
 move the main telescope on its horizontal axis of revolution. If the point remains 
 bisected by the vertical wire of the side-telescope throughout its entire length this 
 adjustment is correct. If not, loosen the capstan-headed screws and rotate the 
 reticule bearing the wires, as explained on page 58, until the wire bisects the point 
 throughout its entire length. Then slightly tighten the capstan-headed screws as 
 explained in "Some Remarks Concerning Instrument Adjustments," page 20. Also 
 see page 58. 
 
 2. To place the intersection of the cross-wires of the side-telescope in its line 
 of collimation. This may be done in several ways. 
 
 (a) The side-telescope being detachable, it could be adjusted by rotating it in 
 wyes, were any at hand. Such wyes, as we have shown before, may be impro- 
 vised by cutting the proper shapes out of thin wood, and fastening a pair of them 
 to a board in au upright position. The distance between them should be such that 
 the telescope may rest upon the outside of the mounting of the object-glass and 
 against its shoulder where the cap is placed, and upon the tube near the cross- 
 wires when practicable. The improvised wyes being placed on a firm support 
 and fastened so that they will not move, the side-telescope may be revolved in 
 them, and the wires may be placed in the line of collimation as in a wye-level, using 
 a distant point. The horizontal wire, being the more important one in the side- 
 telescope, should be placed with some care. 
 
 (b) This adjustment for colliraation may be made without removing the side- 
 telescope, if for the adjustment of the horizontal wire, a small spirit-level* mounted 
 on a metal base, similar to those described on page 119, is at hand. Then proceed 
 thus: 
 
 Adjustment of the horizontal wire, First, level up the instrument by its plate 
 levels. Then, placing the main telescope in a horizontal position by its level s 
 find a well-defined object, such as the target of a leveling rod, distant about 300 feet 
 Now clamp the side-telescope when in a nearly horizontal position to its hub, and 
 placing the auxiliary level, which has been previously adjusted, longitudinally on 
 the side-telescope bring its bubble to the center of the tube by means of the tan- 
 
 * Such a spirit-level mounted in a cast-iron frame, and good enough for this purpose if carefully selected, 
 tut be bought in any of the better equipped hardware stores. 
 
94 
 
 gent screw of the main telescope and now, by turning the instrument on its vertical 
 center see if the horizontal wire of the side-telescope bisects the object or target 
 also. If so, this adjustment is made, but if not, it must be completed by moving the 
 vertical capstan-headed screws as explained on page 58. 
 
 To verity this adjustment, the side-telescope may be reversed on its horizontal 
 axis of revolution and clamped to its hub when nearly in the same level plane. 
 Then turn the instrument a little more than 180 on its vertical center, place the 
 auxiliary level on the side-telescope, same as before, and bring the bubble to the 
 center of its tube by means of the vertical tangent screw. If now, when the side- 
 telescope is in the reversed position the horizontal wire bisects the object also, this 
 adjustment is completed, but if it does not then the horizontal wire must be moved 
 again to a point half-way between the two readings. 
 
 This adjustment may also be made by the auxiliary level alone or by means of 
 a striding-level without the aid of the main telescope (see page 140). 
 
 Adjustment of the vertical wire. Select a well defined object, as a church spire, 
 distant 5 or 6 miles. Bisect it with the vertical wire of the main telescope, and 
 without moving the instrument, look through the side-telescope and note whether 
 the object is also bisected by its vertical wire. If not, make the adjustment by 
 moving its vertical wire by the horizontal capstan-headed screws, until the object 
 is bisected also. The distance between the two telescopes being only a few 
 inches, the vertical wires will cover so great a width, if the object be sufficiently 
 distant, that the effect of the excentricity of the side-telescope will be almost im- 
 perceptible and the same distant point may be used for each telescope. 
 
 (c) When a distant object is not available, measure with a pair of dividers the ex- 
 centricity of the side-telescope, which is the distance between the centers of the two 
 telescopes. Then transfer it to the face of a wall as far distant as practicable and 
 make two marks whose horizontal distance apart is equal to this excentricity. Bisect 
 one of these marks by the vertical wire of the main telescope and then look through 
 the side-telescope and note whether the other mark is bisected by its vertical wire. If 
 not, make it do so by moving the cross-wires of the side-telescope as described on page 
 58. The direction of the lines of sight should be at right angles to the surface upon 
 which the two marks are made. 
 
 The position of the side-telescope with respect to the main telescope should be 
 assured whenever the former is to be used. This may be done as follows : find a mark 
 that is bisected by the horizontal wire of the main telescope. Then turn the instru- 
 ment on its vertical axis and notice whether the horizontal wire of the side-telescope 
 bisects the same mark. If so, firmly clamp the side-telescope to its hub. If not, 
 gently tap one end of the side-telescope, which hitherto has only been loosely clamped, 
 until its horizontal wire coincides with the mark and then clamp the side-telescope to 
 its hub. The telescopes are now set to correspond with the zero of the vertical circle. 
 
 To place the telescopes at an angle with each other. Level up and fix a mark 
 when the main telescope is level. Then raise or depress the main telescope the required 
 angle and clamp the horizontal axis. Now move the side-telescope until its horizontal 
 wire bisects the mark and clamp it firmly to its hub. During an extended operation with 
 the side-telescope, the relative position of the two telescopes should be verified from 
 time to time to detect any disturbance of the side-telescope. 
 
 Transits having the telescope mounted at the end of the horizontal axis of revolu- 
 tion are sometimes used in mines ; or, as shown in the Alt-Azimuths Nos. If a and 16b, 
 this construction is used in some instruments for geodetic and smaller astronomical 
 work. The adjustment of such a telescope for cpllimation may therefore be explained 
 in this connection. The following method is as simple as any : 
 
 Select a well-defined object, as a church-spire, distant at least 5 or 6 miles. The 
 ^istrument being leveled, bisect the object with the vertical wire and read the verniers 
 of the horizontal limb. Then turn the vernier plate so as to read exactly 18u different 
 from the previous reading, and revolve the telescope. If the vertical wire is adjusted 
 for collimation it will again bisect the distant object, since the space covered by the 
 cross- wires on an object at such a distance will be much greater than the change in the 
 position of the telescope as caused by its excentricity from the center of the instrument. 
 If it does not again bisect the object, correct one-half the error by means of the hori 
 zontal capstan-headed screws as explained on page 58. 
 
95 
 
 The adjustment of the horizontal wire for coilimation may be made by selecting 
 one of the methods best adapted for a particular design of telescope. 
 
 These two adjustments should be repeated until both are correct. 
 
 To measure the excentricity of the telescope, set up the instrument as near to 
 a wall or other vertical object as possible. Draw a horizontal line upon the wall 
 at a convenient height. Point the telescope exactly at right angles to the wall, 
 mark where the vertical wire intersects the line just drawn, and read the verniers 
 of the horizontal limb. Turn the vernier plate exactly 180, revolve the telescope 
 and make a second mark where the vertical wire now intersects the line. The dis- 
 tance between these two marks will be twice the excentricity of the telescope. 
 
 When using an instrument of this description for short sights, it is very con- 
 venient to use sighting poles with excentric targets, or an offset at the foot of the 
 pole corresponding to the excentricity of the telescope. 
 
 The Auxiliary Top Telescope, 
 
 Now superseded by the interchangeable auxiliary telescope, see style I. 
 
 This auxiliary, as previously made by us, was mounted in adjustable wyes on 
 standards permanently fixed to the main telescope, so that both lines of sight could 
 be made parallel. The weight of the top telescope was balanced by a counterpoise 
 attached to a stem also permanently fixed to the cross-axis of the main telescope. 
 When the top telescope was not in use it was kept in the instrument box, while the 
 standards and counterpoise stem were permanently fixed to the main telescope so as 
 to avoid frequent and tedious adjustments. This feature made the instrument 
 troublesome and unwieldy for the more ordinary work in mines, and still less con- 
 venient for surface work. 
 
 This improvement when first introduced by us superseded all other forms of top 
 telescopes as made by others whose main object seemed to be simply to straddle an- 
 other telescope above the main one (a mere commercial article, not an instrument 
 of precision) for the purpose of steep sighting. But since the line of sight of such a 
 telescope can never be placed truly at right angles to the cross-axis, the line of coili- 
 mation does not move in a truly vertical plane, therefore horizontal angles measured 
 between points differing greatly in elevation or in distance are never correct. 
 
 It can also be readily seen that the telescope of a solar attachment as commonly 
 made, having no means of lateral adjustment to the main telescope, is insufficient in 
 this respect (even leaving aside its low power and aperture) and cannot meet tlie 
 requirements properly. The adjustment by which the line of coilimation of top 
 telescope is placed in the same vertical plane as that of the main telescope is just as 
 important as that of the main telescope itself. 
 
 A most convenient and practical device haying all the advantages of that former 
 style, i. e., means of adjusting the line of coilimation parallel to that of the main 
 telescope, so that after having been removed it will retain its adjustments when again 
 attached, is our new mounting of the top telescope by means of threaded studs. This 
 enables the engineer to read horizontal angles when the main telescope cannot be 
 used, obviating the making of corrections for the eccentricity of the telescope. 
 
 Patent Adjustable Top Telescope. 
 
 This device consists of an adjustable auxiliary telescope (see pages 189 and 
 193) and an open central pillar, which latter screws to a threaded stud cast on or 
 permanently secured to the cross-axis of the main telescope. When not needed, 
 the auxiliary telescope and its counterpoise may be returned to the box and the 
 instrument is free of incumbrances, save the stem for the counterpoise and the 
 stud to which the central pillar carrying the auxiliary telescope is attached, and is 
 ready for surface work. . If desired, the top telescope may be entirely unscrewed 
 from the central pillar, leaving the latter attached to the main telescope. 
 
 The Adjustment of the Auxiliary Telescope used as a Top Telescope: 
 It is assumed that all adjustments of the transit proper have been made, that is, 
 that the plate and telescope levels, the line of coilimation, the vertical plane, etc., 
 have been verified and corrected, and that the verniers of the vertical circle read 
 
96 
 
 zero when plates are leveled up and that the bubble of the telescope level is in the 
 center of its graduation. 
 
 The, adjustment of Line of Collimation of Auxiliary Telescope : First examine the. 
 coincidence of the intersection of the cross wires with the optical axis. This may 
 be done by rotating the telescope in improvised wyes of wood (see p. 93), or by 
 rotating it in the socket of the pillar [as sometimes made by us] by unscrewing it 
 about one turn, when the adjustment is made by moving the capstan-headed screws 
 as described on page 58. The telescope must now be screwed to its bearing in such 
 a manner that the cross-wires are parallel to those of the main telescope to be veri- 
 fied as explained in "To make the vertical wire perpendicular to the plane of the 
 horizontal axis," etc., p. 54. 
 
 To place the line of collimation of the auxiliary telescope in the same vertical plant 
 with that of the main telescope. Bisect a distant object with the vertical wire of the 
 main telescope ; see if the venical wire of the auxiliary telescope also bisects the same 
 point. If not, move the auxiliary telescope by means of the pair of opposing milled- 
 headed screws attached to its pillar nearer the eye-end until the distant object is 
 bisected at the same time by both vertical wires. Now focus the main telescope on a 
 near object and see if the vertical wire of the auxiliary telescope bisects the same 
 point as the vertical wire of the main telescope. If not, make the adjustment by 
 means of the pair of capstan-headed opposing screws on one side of the adjusting 
 trivets of the pillar. Then re-examine both wires for coincidence with the distant 
 object, u-ing the milled-headed screws, and also repeat the adjustment for near object 
 if necessary. The two lines of collimation are now in the same vertical plane. 
 
 To adjust the top telescope so that both horizontal wires bisect the same distant 
 object. Bisect a distant object with the horizontal wire of the main telescope, and see 
 whether the horizontal wire of the auxiliary telescope bisects the same point. If not, 
 make the coincidence by means of the pair of opposing capstan screws in the trivets 
 near the milled-headed screws. This being done, both these adjustments should be 
 verified and repeated if necessary. These adjustments once carefully made assure 
 the exact parallelism of both telescopes and will not require repetition except at long 
 intervals, or after an injury. 
 
 The distance between the lines of sight of the two telescopes should be carefully 
 measured by sighting at a vertical line on a wall the telescopes being horizontal 
 when the distance between the intersections of the two horizontal wires on the line will 
 be the eccentricity of the top telescope, for which every vertical angle measured with 
 it should be corrected. 
 
 The Berger Style I Interchangeable Auxiliary 
 Telescope (Patented). 
 
 See pages 189 and 193. 
 
 In this device Style I, the auxiliary telescope screws direct upon an open central 
 vertical post cast in one piece with the transverse axis to secure great rigidity, the 
 degree of accuracy of the result depending in a large measure upon the degree of 
 accuracy with which the center of the pillar, and the line of collimation of the prin- 
 cipal (then vertical) wire of the auxiliary telescope are made to lie in the same verti- 
 cal plane as the optical axis of the main telescope or parallel to it. With the care 
 given to it and special machinery used for it, this condition, difficultas it is, is secured 
 to an extent which leaves little to be desired for all practical purposes. As the aux- 
 iliary telescope is inter changeable from top to side there is really need of but one wire, 
 which we will designate as the principal wire. This, when the auxiliary is mounted 
 on top, is the vertical wire, and when on the side becomes the horizontal wire. There- 
 fore it will be seen that when the auxiliary is mounted on top the line of collimation 
 of its horizontal wire is immaterial, as no vertical angles will then be measured. 
 When the latter are to be measured the engineer will then mount the auxiliary on 
 the side, when in turn the vertical wire becomes immaterial. The auxiliary tele- 
 scope is provided with two milled-headed opposing screws for ranging in line with the 
 main telescope. The auxiliary telescope's adjustment of collimation and coincidence 
 of the cross-wires and optical axis must be verified by the use of improvised wooden 
 wyes (see above), should it become necessary. 
 
 The success which the interchangeable auxiliary telescope has achieved, both 
 here and abroad, since" first invented by this firm in 1895 is somewhat phenomenal. 
 It shows that this combination is the most applicable one in solving the difficult 
 problems arising in mine engineering. For this reason every preparation has been 
 made to meet the demand and new improvements are added as experience may sug- 
 gest. All our top telescopes are therefore now made interchangeable. 
 
97 
 
 The Use of the Interchangeable Auxiliary Telescope 
 for Astronomical Observations. 
 
 Besides its ordinary use for steep sighting in mines, the interchangeable auxiliary 
 telescope, as described in the foregoing article, will at times be found very useful as 
 an astronomical instrument. It is particularly advisable in making latitude observa- 
 tions by meridian altitude and in observing transits across the meridian for time. As 
 a rule when the prism is attached to the eye-piece of the main telescope it is not pos- 
 sible with the engineer's mining transit to point the telescope at a greater angle of 
 elevation than about 70, consequently it would be impossible to make solar observa- 
 tions at a latitude lower than 40 when the sun is at its greatest declination or obser- 
 vation on Stars near the zenith. However, by attaching the prism to the auxiliary telescope 
 used asatop or sidetelescope, these observations may be made witheasenndthisdifficulty overcome 
 
 In making latitude observations the interchangeable auxiliary telescope should be 
 attached at the side ; and its horizontal wire is then, by means of the two oppos- 
 ing tangent screws, made to correspond to the line of collimation of that of the main 
 telescope by bisecting with both telescopes some distant and well-defined object : then, 
 if a meridian mark is used (which is not absolutely necessary), the transit should be 
 set up in the meridian by the main telescope and the pointing on the sun or star may be 
 made with the auxiliary telescope with or without the prism, as conditions may require. 
 
 In observing transits the auxiliary telescope should be mounted on top and ranged 
 into line with the vertical wire of the main telescope by using the two opposing 
 screws as explained. 
 
 In making solar and stellar observations with the main telescope and prism attachment, the tele- 
 acope should always be reversed through the standards with the objective down instead of up 
 
I 
 
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 35 
 
99 
 
 Magnetic Needle of Edge-bar Form 
 
 The needle shown in the cross section of our Transit compass also in the top view 
 on opposite page, represents the form adopted and preferred by us for all of our com- 
 pass instruments, because it has its greatest dimensions in the vertical direction ; hence 
 its name. At the ends, where it is read, it is quite thin, but increases in thickness 
 symmetrically towards the central part to give it the rigidity necessary to retain the true 
 longitudinal shape and yet be very light of weight to minimize the dulling of the pivot 
 on which it swings. The point of suspension in the steel cap* and the two ends of the 
 needle are in a straight line, thereby forming the geometric axis. 
 
 The advantage derived from the edge-bar form, therefore, is that its mag- 
 netic axis must be contained in the geometric axis of the needle, whence it 
 follows that there is no index error at its reading ends. 
 
 This cannot be claimed for a needle of the flat, oblong type, since its magnetic 
 axis may follow the grain imparted to it in rolling the steel ingot. In such a needle 
 the index error may be negligible or amount to a great deal, according to size and 
 shape. Hollow, cylindrical, and elliptically shaped needles are not exempt from this 
 error, and as their ends require brass extensions for reading the graduation in a sur- 
 veyor's compass, the effective length of the needle is not only shortened, but the exten- 
 sions in themselves may become an additional source of index error. As will be seen 
 in the cross section, the center of gravity in the edge-bar form is very much below the 
 point of suspension, which, together with the increasing weight of the needle toward 
 its central part, makes it less sensitive to dip. The quivering of a needle so constructed 
 is not annoying, since the center of its quivering motion is in line through its two ex- 
 treme points, which are, therefore, stationary. Permanent magnet steel is used only 
 in its construction, which, when properly hardened, will, at all times, retain sufficient 
 magnetism to give the needle direction when resting on a sharp point. It is the dulling 
 of the latter t which is commonly at fault when a needle does not settle repeatedly in 
 the same place not loss of magnetism as is generally supposed and most of this 
 difficulty may be obviated by carefully raising or lowering the needle and not allowing 
 the needle to play when shouldering the instrument. To be light the steel cap is mounted 
 in an aluminum cell. 
 
 * It is our belief that no advantage whatever is gained by suspending the needle on jewel 
 bearings, but that a properly tempered steel bearing, resting on a steel pivot of a different temper, 
 is superior to the jewel mounting. We find that in the instruments sent us for repair the jewels 
 are almost always grooved by the wear of the pivot so that it is difficult, or impossible, to repair 
 them satisfactorily. With steel bearings no such difficulty is encountered. As to danger of rust- 
 ing, it is certainly no greater for the bearing than for the pivot, and the instruments sent in for 
 repair do not often show signs of either bearing or pivot rusting. 
 
 t In order to partially remedy the wearing on the point we sometimes, upon special request, furnish a 
 needle of twisted form which can be made very Tight and be quite stiff in proportion to its weight. It is not 
 of a strictly -scientific shape but answers the requirements of a Surveyor's Compass. , ; The needle consists of a 
 flat bar of ye 5 thin permanent magnet steel. At the central portion of; the ,bar, the blade is horizontal, 
 while at the ends it is vertical as in the edge-bar form of needle. Between the center and the ends there are 
 several twists in the bar. The points of the needle and the point of suspension are all in the same straight 
 line in this new needle, as in the old. The center of gravity is placed as far below the point of suspension as 
 the necessarily limited depth of the Transit compass permits, but owing to its extreme lightness the center of 
 gravity should be carried much farther bilow than the old to counteract the dip to the same extent. In conse- 
 quence tlie needle of twisted form is more easily affected by change in latitude and its 
 application is, therefore, limited, to use within latitudes differing not more than a few degrees. 
 
 Caution. 
 
 The magnetic needle must always be lowered very gently on its pivot. The 
 knob marked "Lifter" (see page 98) raises and lowers the needle. If the needle is 
 lowered abruptly upon the pivot, its fine point may be dulled the first time, and the 
 needle will then work sluggishly and not settle twice in the same place. 
 
 To use the Variation Plate, insert an adjusting pin into the capstan-headed nut 
 beneath the "Lifter," and by turning either way the desired declination may be set 
 for East or West. 
 
100 
 
 Berger Short Focus Lenses. 
 
 A sectional view of a Berger Short Focus Lens attached to 
 an Erecting" Transit Telescope. 
 
 No. 1 and 2 Lenses. 
 
 No. 1 Lens. 
 
 The above lenses may be attached separately or together, as 
 shown; for a complete description see opposite page. 
 
101 
 
 The Berger Short Focus Lens Attachment. 
 
 A very valuable addition to the engineer's outfit is found in the short focus lens 
 attachment which has been brought out. The contrivance is simple, but, like many 
 simple devices, is very effective in overcoming a practical difficulty. Probably every 
 engineer has been annoyed by being obliged to sight a point a little too near for the 
 telescope to focus. Most transit telescopes will not focus on a point much nearer than 
 6 or 6 feet (levels not nearer than 7 or 8 feet) away from the instrument, while it is 
 frequently necessary to sight a point on the ground nearly under the transit, at a dis- 
 tance which is usually less than that. 
 
 In mine surveying as well as inside of factory buildings, one frequently needs to 
 sight a point overhead or on the walls and very near the transit. Ordinarily the only 
 way out of the difficulty is to focus as nearly as possible and do the rest by a guess. 
 As a further instance, one often finds in leveling, that it will be necessary to take 
 a reading on a point very near the instrument, and has to resort to various means 
 (all of them inaccurate) of getting around the difficulty. The attachment men- 
 tioned consists of a small aluminum tube containing a simple lens, which is attached in 
 front of the objective. The lens is so placed in the tube that it can be accurately 
 centered by means of 4 adjusting screws. The effect of this lens is of course to bring 
 rays to a focus nearer to the objective, and thus enable the observer to focus a nearer 
 object than would otherwise be possible. When the telescope will focus no nearer than 
 6 feet, the attached lens, marked 1, is ground so that it will focus objects 6 feet away 
 when the objective tube is drawn away in. This allows the entire motion of the focusing 
 slide for distances between 6 and 4 feet. For distances nearer than 4 feet a second 
 lens may take the place of the first and will focus up to about 2| feet. If the two are 
 used at once the distance is reduced to about two feet. 
 
 With this pair of lenses there is no distance between two feet and infinity at which 
 objects cannot be focused. The accuracy of work done with this attachment is in no 
 way affected by the centering of the attached lens itself, as this is capable of perfect 
 adjustment. The only way in which error can occur is through the imperfection of 
 the objective tube. If the cylindrical surface of the object-head of the telescope on 
 which the attachment is placed is not concentric with the optical axis of the teles- 
 cope this error will enter into the adjustment of the attached short focus lens. This 
 error, however, is never large on an instrument sent out by our firm. But even 
 admitting that there may be some error here, it must be rememembered that this lens 
 is never used for objects more than about 6 feet away ; consequently the resulting 
 error on the point is entirely negligible, and the convenience of the attachment: 'n 
 many cases is so great that it entirely outweighs any such consideration, since the 
 work done at this distance will be entirely consistent with the work done with the 
 instrument on the longer distances. The attachment fills a want that has long been 
 felt by engineers and is certainly a step in advance in the perfection of instruments of 
 precision. 
 
 To attach this device to their old instruments it will be necessary to send the instru- 
 ment to them, as every lens attachment must be specially fitted and centered. How- 
 ever, it can be supplied with any of their new instruments, either Transits or Levels, 
 made since 1899. 
 
 When attached to transits, No. 1 permits focusing objects to about 3 feet, No. 2 
 permits focusing objects to about 2^ feet : both permit focusing objects to about 2 feet 
 from center of instrument. 
 
 This is so important a feature that one trial will convince one that it is indispensa- 
 ble to the outfit of an engineer The device is patented. The Messrs. Berger 
 are also prepared to attach it to their Wye and Dumpy level, lor focusing nearly aa 
 close as stated above for transits. For pi-ices see catalogue, page 203. 
 
102 
 
 NOTE. 
 
 In selecting instruments from catalogues, engi- 
 neers should not be led so much by a simple com- 
 parison of prices, as by the advantage offered in 
 superior merits, working capacity, and preservation 
 of fine qualities in case of severe treatment. We can 
 cite instances, where transits and levels of our man- 
 ufacture had severe falls, resulting without injury to 
 any part of instrument not even disturbing the 
 adjustments. 
 
 A larger outlay of $1O or $2Q in the purchase 
 of a superior article is a great saving in time and 
 expense in the end. 
 
 Owing to the great variety of styles and combina- 
 tions enumerated with our instruments (which com- 
 binations may easily be carried into the hundreds) the 
 principal combinations only are provided for in the 
 code at the back of the catalogue and Code names 
 underlined indicate customary instruments which we 
 intend to carry in stock. A large stock of these instru- 
 ments is kept on hand, but owing to the very many 
 combinations of sizes and styles and to the great de- 
 mand, at times the instruments desired may have to be 
 made specially, nevertheless. It is therefore advisable 
 to order all instruments as far as possible ahead of the 
 intended for their use. 
 
- CABLE- 3AGf<- BOSTON- 
 
 LABORS .T VJRTVTE 
 
 M [ .- ,.... I i . i r-. '"'ink ^J 
 
 ESTABLISHED 
 
 Jc)7J 
 
 LIST AM 
 
 OF 
 
 INSTRVTUENTS 
 
 OF PRECISION FOR 
 SVRVEYORS 
 
 ENGINEERS 
 AND ASTRONOMERS 
 
 MADE BY i 
 
 CLBERGERfrSONS 
 
 BOSTON, MASS. 
 
 
RIBBING PARTS OF INSTRUMENTS. 
 
 Patrons will notice the omission in this edition 
 of illustrations of the practice of ribbing and con- 
 struction of parts of our instruments to gain strength 
 and lightness. 
 
 We omit the illustrations of these improvements, 
 introduced by us since 1871, because now they are 
 in common use. 
 
 The cuts in this catalog show the lines on which 
 we are advancing these improvements to an extent 
 hitherto unknown. 
 
 ALUMINUM. 
 
 We omit cuts in former editions of parts of in- 
 struments made of aluminum alloys, because said cuts 
 do not express the wider range of use to which these 
 alloys are being applied by us today to instruments of 
 special design for special purposes. 
 
 Nevertheless, in the present state of these alloys 
 it is incumbent upon us to say that the opinion ex- 
 pressed in Part I of this catalogue must still gener- 
 ally be adhered to. 
 
 These alloys, in the construction of field instru- 
 ments, must be used with extreme caution and judg- 
 ment to give satisfaction. 
 
 104 
 
G- 
 
 H 
 
The Berber Complete Engineers' and Surveyors' Transit No, Ic. 
 
 For description and prices see Engineers' and Surveyors' Transit. ; 
 
The Berger Complete Mine Transit No. 4. 
 
 With Style I interchangeable auxiliary telescope. 
 (Horizontal circle either 4 or 4> inches.) 
 
 For description and prices see Mine Transits. 
 
[Patented) 
 
 The Berber Complete Mine Transit No. 4k. 
 
 With edge graduations and fully enclosed vertical circle. 
 
 For description and prices see Mine Transits. 
 
115 
 
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 Spirit Levels. 
 
 For the benefit of our patrons we enumerate below the principal Spirit Levels we are prepared to supply 
 at short notice. They are made by us, and are of the same superior quality as those furnished with our instru- 
 ments. In the list below we give length, diameter, and degree of sensitiveness. They are graduated, as a 
 rule, as shown above. Levels different in size from this list can be made to order only, and will be furnished 
 only when order is accompanied with the tube or mounting for which one is intended, and also stuting the 
 kind of instrument it is for, and the degree of sensitiveness desired. We will positively not make any levels 
 upon written dimensions only, but require the tube to be sent in all cases, as otherwise we will not be respon- 
 
 sible 
 WO. 
 
 2. 
 3. 
 4. 
 5. 
 
 6. 
 7. 
 
 8. 
 
 or any failure in that re 
 Length from tip to 
 tip in Inches. 
 6.50 to 6.60 
 4.75 
 4.10 
 300 
 2.40 
 2.00 to 2.25 
 1.68 - 
 
 spect. Please read paj 
 Diameter in Inches. 
 
 0.75 to 0.80 
 0.65 to 0.68 
 0.58 to 0.60 
 0.51 to 0.53 
 0.51 to 0.53 
 0.41 to 0.43 
 0.41 to 0.43 
 
 jes 6 and 15. 
 Sensitiveness. 
 
 One div. (0.10) = 10" to 20" of arc 
 (0.15) =15" to 20" ' 
 (0.15) =15" to 20" ' 
 (0.10) =20" to 25" ' 
 (0.10) =60" 
 (0.10) = 70" 
 (0.10) = 75" 
 
 Price mounted, 
 if tube is re- 
 turned. 
 $4.50 to 5.00 
 3.50 to 4.00 
 3.80 
 3.20 
 1.80 
 1.80 - 
 1.80 
 Price 
 unmounted, 
 50 cents less. 
 
 Mi 
 
 C. L. Berger & Sons' Quick Leveling Attachment. 
 
 Shown as applied to Lercl* and Transits. 
 
 (See page 45 of Manual.) 
 
 Code Word Entroba for use with Transit No. 4 $2O.OO 
 
 Epilobium for all other sizes 15.OO 
 
119 
 
 Code word . . Oakadum. 
 
 Spirit-Level on Metal Base. 
 
 Ground Spirit-Level, one division of level about 20 sec. of arc ; mounted on 
 8-inch metal base, provided with a handle. Level adjustable. In case. 
 
 Price, $14.OO 
 
 These levels are extensively used in machine shops for leveling up and testing 
 fine machinery, etc., also used for leveling up apparatus in observatories, physical and 
 chemical laboratories, and for setting weirs, etc. 
 
 Code Word 
 
 Oakesia. 
 
 Brass or nickel-plated. 
 
 Locke's Hand-Level. 
 
 In case 
 
 Price $8.OO 
 
 NOTE. This consists of a brass tube 6 inches long, with a small level mounted on its top to the left of its 
 center near the object end. Underneath the level is a horizontal wire stretched upon a frame. This frame is 
 made adjustable by a screw and a spring working against each other, or by two opposing screws placed at the ends 
 of the level mounting. In the tube directly below the level is placed a totally reflecting prism, acting as a mirror 
 set at an angel of 45 to line of sight. The images of the bubble and wire are thus reflected to the eye. 
 The prism divides the aperture in two halves, in one of which is seen the bubble and wire focussed sharply by 
 a convex lens placed in the draw tube, while the other permits of an open view. Putting the instrument to 
 the eye and raising and lowering the object-end until the bubble is bisected, natural objects can be seen through 
 the open half at the same time, and approximate levels can then be taken. To prevent dust and dampness 
 from entering the main tube, both the object and the eye ends are closed up with plain glasses. la preliminary 
 work this is a very useful instrument. 
 
 Hand-Level and Clinometer. 
 Abney Level and Clinometer. Price $14.OO. 
 
 NOTE. This instrument is similar to the Locke's hand-level, but the small spirit level mounted on top 
 can be moved in the vertical plane and clamped to a dial graduated in single degrees, thus the angles of slopes, 
 etc., can be measured also. 
 
 Code Word . . . Oleander. 
 
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19.1 
 
 Tripods for the Engineers' and Surveyors' Transits 
 
 and Levels. 
 
 For description see page 7; for prices and weights, if extra ones are desired, see 
 preceding page. 
 
122 
 
123 
 
 C. I,. BKRGEK & SONS. BOSTON 
 
 Road Builder's 
 MONITOR TYPE DUMPY LEVEL. 
 
 A sturdy, compact instrument of smaller size and less weight than our 
 14^" Monitor Type Dumpy L,evel. 
 
 This instrument has been designed by us to meet a growing want for the high- 
 way as well as for the Drainage Engineer. The degree of accuracy obtained with 
 it is commensurate with the work required. The telescope is erecting and has 
 lenses of perfect definition with a large flat field of view and is balanced from the 
 
 center with Sunshade attached. The eye-piece cap is large in diameter and made so 
 that it affords a protection to the observer's eye in a glaring sun. It has been com- 
 bined with a dust-guard which fully protects the eye-piece focussing slide. 
 
 The spirit level is very sensitive and is mounted on top of the telescope. It is 
 protected by a revolvable tube to act as a guard to prevent breakage when not in use. 
 
 The leveling head is of a single casting of improved form, so that the center will 
 not bind in the socket from any strain exerted by the four leveling screws which lat- 
 ter are protected from injury and dust. 
 
 We have adopted for this level Our standard long stout center with which all of 
 our instruments have been identified, thus adding to its Stability. 
 
 This level will withstand rough treatment. The adjustments are few,* when 
 once made they are lasting and above all the instrument is dependable at all times 
 and free from any tremor even in a strong wind. Its rounded forms, together with 
 
 the fine, dark and durable wear resisting leather finish applied to the exterior 
 surfaces, appeal to anyone in sympathy with advanced instrument design. 
 
 SPECIFICATIONS : 
 
 Telescope Erecting" 12 inches long, aperture 15i", power 24 dia. Focuss- 
 ing slide very long and provided with a dust guard. 
 Eye-piece with large flat field of view, provided with an improved screw 
 
 arrangement permitting to focus the wires by simply turning its head slightly 
 
 to right or left. 
 Spirit Level 5% inches long between centers of suspending arms. The spirit 
 
 level is very sensitive and accurately ground to a true curvature and barrel 
 
 shape. 
 Center of hard bell metal. 
 
 Mahogany box provided with strap, lock, and hooks, contains sunshade 
 
 wrench, scre\vdriver and adjusting pins. 
 
 Weight of Instrument 7 Ibs. Weight of tripod about 9 Ibs. 
 
 Gross weight of instrument securely packed for shipment in two boxes about 
 
 35 Ibs. 
 Code word: Oleaster. Price as above $75.OO 
 
 Extras to 12" Monitor Type Dumpy Level. 
 
 Stadia Wires fixed in ratio 1 : 100 *3.oo 
 
 Gossamer water-proof bag to protect the instrument in case of rain or dust i.oo 
 Bottle of fine watch-oil to lubricate the lever center .... .35 
 
 * The above instrument, being of the Dumpy level type, has to be adjusted by the two peg 
 
14 
 
 124 
 C. L,. BEKGEK & SONS. BOSTON 
 
 111 MONITOR TYPE DUMPY LEVEL. 
 
 2 Tubular Bar 
 
 A sturdy, compact instrument of precision. For use in the Army, about For- 
 tifications, in Cities, Construction of Highways, Railroads, Tiiimels, Mines, 
 and about Factories, etc., where a smaller size and less weight is desirable. 
 
 In answer to many inquiries for a Dumpy Level to take the place of the frail 
 and often badly designed 14 inch w y e Levels, commonly found on the market, we 
 are offering this most advanced type. 
 
 The Monitor Type Dumpy Level is made to last, its vital parts are 
 
 strongly built in a stubby style. The center flange and the clamp and tangent screw are 
 carried up very far into the hollow bar thus reducing the height of instrument to the 
 tripod head and are protected from rain, dust, grit and injury. All this has been ac- 
 COmplished without sacrificing the standard long center with which all of our in- 
 struments have always been identified, thus adding to the stability of the instrument. 
 The hollow bar is tubular in form and therefore is deflection resisting. A far greater 
 amount of rigidity will be found in the Monitor type level bars which are greatly 
 superior to those of the older familiar forms of same weight. These bars are not 
 affected by temperature changes owing to the free circulation of air through and 
 around the bar. 
 
 The telescope tube is made of a single casting and bored out to be truly cylindrical 
 (not made of tubing, which is often Oval in form, See page 128). The leveling head 
 is also of a single casting of improved form, so that the center will not bind in the 
 socket from any strain exerted by the four leveling screws. Owing to the peculiar 
 
 construction of the socket the center-clamp screw cannot exert any pressure upon 
 the center after the instrument is clamped to the socket, thus leaving the bubble 
 undisturbed. 
 
 This Level will Avithstand all kinds of rough treatment when transported On mule- 
 
 back, over mountains, impassable roadsor throughthe wilderness. The adjustments 
 
 are few, when Once made they are lasting and above all the instrument is de- 
 pendable at all times and free from any tremor even in a strong wind. Its rounded 
 
 forms, together with the fine, dark and durable wear resisting leather finish applied 
 to the exterior surfaces, appeal to anyone in sympathy with advanced instrument 
 design. The telescope is erecting. 
 
 SPECIFICATIONS: 
 
 Telescope Erecting 1 14# inches long, aperature 1^, power 30 dia. 
 
 Focussing slide very long and provided with our collapsible dust guard, see 
 page 128. 
 
 Eye-piece with large flat field of view, provided with an improved screw 
 arrangement permitting to focus the wires by simply turning its head slight- 
 ly tO right Or left. The eye-piece cap is large in diameter and made so that it 
 affords a protection to the observer's eye in a glaring sun. It has been combined 
 
 with a dust-guard which fully protects the eye-piece focussing slide. 
 Spirit Level O inches long between centers of suspending arms. The spirit 
 
 level is very sensitive and accurately ground to a true curvature and barrel 
 
 shape. 
 
 Center of hard bell metal. 
 Clamp and Tangent Screw. 
 
 Mahogany box provided with strap, lock, and hooks, containing sunshade, 
 
 wrench, screwdriver and adjusting pins. 
 
 Weight of instrument 9/2 Ibs. Weight of tripod about 9 Ibs. 
 
 Gross weight of instrument securely packed for shipment in two boxes about 
 
 40 Ibs. 
 Code word : Alodol Price as above $ 1 15 
 
 Extras to 14^ inch Monitor Type Dumpy Level. 
 Stadia Wires fixed in ratio 1 : 100 *:J.oo 
 
 Steel Center running in a cast iron socket to insure freest motion with 
 
 perfect fit 10.00 
 
 Fine mirror mounted in case with universal joint. (This is readily at- 
 tachable to either side of the instrument and facilitates the reading 
 of the bubble on soft ground without stepping aside) . . . 10.00 
 
 Gossamer water-proof bag to protect the instrument in case of rain or dust i.oo 
 
 Bottle of fine watch-oil to lubricate the lever center .... .35 
 
 MONITOR TYPE DUMPY LEVEL. 
 
 Inverting Telescope. Aperture, Power and Price same as above. For descrip- 
 tion and cut see pages 126-127. (Code word: Abardo.) 
 
C. I,. UKKGKJl & SONS. BOSTON 
 
 r 
 H 
 
 i r 
 
 * 2 
 
 5 "* 
 
 
 
 i H 
 
 } if if 
 
 IM s 
 
 ! 1 5 ? 
 I? ? 
 
 14 
 
 Code Words for 14^ iiu-h Dumpy levels, 
 
 inch erecting telescope ........ 
 
 inch erecting telescope with fixed stadia wires 
 
 Alodol 
 Abadc'iio 
 
C. t. BKKGER & SONS. 
 
 1 5" AND 1 7|" MONITOR TYPE DUMPY LEVEL. 
 
 An instrument of great precision, superior to any Wye Level of same, aperture, 
 power of telescope, and same sensitiveness of spirit-level. The best instrument for 
 use in distant lands and rough country on account of its great compactness, 
 simplicity, strength to withstand rough treatment, permanency of adjust- 
 ments, and steadiness in a strong wind, requiring but ordinary attention and 
 care to keep in working order. For a fuller description, see page 128. 
 
 This new type of Dumpy Level with round, hollow, and very long cross-bar, must 
 be considered the most perfect in this line. It stands low on the tripod, and its fine 
 spirit-level, being placed in the hollow cross-bar, below the telescope, can be read from 
 either side, and is entirely protected from accident and liability to derangement of ad- 
 justments, also from the disturbing influences of the heat of the sun, touch of fingers, 
 breath, etc. These latter conditions are not fulfilled in instruments where the level is 
 placed on top or at the side of the telescope, and are frequently causes of the incorrect 
 reading of the bubble. This instrument is of very strong build, combined with a mini- 
 mum of weight, and as it consists of a fewer number of pieces than the Wye Level, is 
 less liable to derangement in case of accident. The adjustment once properly made by 
 the two peg method (see adjustment of Dumpy Level, page 63) is apt to stay so for 
 years, thus removing one of the chief objections as compared with those of a Wye 
 Level. In making the adjustment of this Dumpy Level the engineer does not depend 
 so much on mechanical perfection, as on his own superior skill and sense of accuracy. 
 
 To meet an urgent demand this type of Dumpy Level is now provided with a 
 clamp and tangent screw to enable, in a strong wind, to keep the telescope upon an 
 object, and, although it raises the price, it will prove an invaluable accessory, well 
 worth the extra cost. This instrument is leather-finished. 
 
 The telescope can be inverting or erecting; see cuts on pages 127 and 129. 
 The objective in either case will have the same aperture. 
 
 We recommend this instrument highly for all work of a high character, such as 
 bench leveling, water-works, railroad construction, also for reconnoissance. 
 
 SPECIFICATIONS : 
 
 Inverting 15 inch long, aperture 1^, power 28 dia. 
 Erecting 17 % inch long, aperture 1^, power 32 dia. 
 Focussing slide very long and provided with a dust guard when run out for sights 
 as near as about 12 feet. 
 
 Eye-piece with large flat field of view, provided with an improved screw 
 arrangement permitting to focus the wires by simply turning its head slightly 
 to right or left. 
 
 Spirit Level 7 ' ^ inches long between centers of suspending arms. The spirit 
 level is very sensitive and accurately ground to a true curvature and barrel shape. 
 Center of hard bell metal is cast in one piece with the hollow cross bar. 
 Clamp and Tangent Screw 
 
 Mahogany box provided with strap, lock, and hooks, containing sunshade, wrench, 
 screwdriver and adjusting pins. 
 
 Weight of instrument 10 Ibs. Weight of tripod about 10 Ibs. 
 Gross weight of instrument securely packed for shipment in two boxes about 50 Ibs. 
 Codeword: 15 inch inverting telescope Abardo 
 
 " " 17fc" erecting " Aciiia Price ' each as above ' $115 
 (For Code Words of Extras below, see page B of complete code at back.) 
 
 Extras to 5" and !7 1 /" Dumpy Levels. 
 
 Stadia Wires fixed in ratio 1: 100 . ... $3.OO 
 
 Steel Center running in a cast iron socket to insure freest motion with 
 
 perfect fit, see page 134. (Made to order only.) 1O.OO 
 
 For quick leveling attachment see page 118. . . 15.OO 
 
 Fine mirror mounted in case with universal joint. (This is readily attach- 
 able to either side of the instrument and facilitates the reading of the 
 bubble on soft ground without stepping aside) . . . 1O.OO 
 
 Gossamer water-proof bag, to protect the instrument in case of rain or dust l.OO 
 
 Bottle of fine watch-oil to lubricate the level center .35 
 
 A detachable Vernier Compass, with variation setoff E & W and with 3'/ 
 inch needle, can be mounted on top of these Dumpy Levels at an extra expense 
 of $16.OO. Made to order only. 
 
127 
 
 C. L. BEKGEH & SONS. 
 
 
 
 5 S- 
 
 Code Words for Dumpy Levels. 
 
 16-inch Inverting Telescope 
 
 J5-in"h Inverting Telescope with fixed stadia wires . 
 
 Abardo 
 Abella 
 
 (For Extras and changes from Abardo and Abello see page B of complete code at back,) 
 
C. 
 
 1-28 
 BEKGEU & SONS. 
 
 Monitor Type Dumpy Level. 
 
 Additional Information pertaining to its mechanical Construction. 
 
 From the illustrations, pages 127, 129, it will be seen that the mechanical parts of 
 this Dumpy Level are few and can easily be made to be mechanically correct, and that 
 there are no working strains whatever in the metal to exert an undue influence upon the 
 adjustments with changes of temperature. 
 
 The telescope barrel and both uprights are cast in one piece of hard composition 
 metal; and in order to arrive at a high degree of accuracy the barrel is bored out to be 
 truly cylindrical, a condition never attained by the use of drawn tube. (For reasons 
 mentioned later both ends of the outside tube are slightly larger in diameter, forming 
 collars turned truly concentric to the bore, serving in principle the same object as collars 
 of a Wye Level telescope.) This being accomplished, the bottom surface of the uprights 
 is turned truly parallel to the bore. The strongly-ribbed cross-bar and instrument center 
 are cast in one piece of hard bell-metal. At the time when the center about which the 
 instrument revolves is fitted to its socket, the resting-places for the uprights are also turned 
 off so as to be truly at right angles to it, from which follows that the geometrical axis of 
 the telescope barrel when latter is placed upon them must also be at right angles to the 
 center. The level casing, too, is a casting. The spirit-level itself is fastened into this cas- 
 ing by a superior method to preclude any strain, so that its true form may "be preserved, 
 The focusing slide is the only tube made of brass, turned and closely fitted in the lathe. 
 
 In adjusting this instrument in the shop it is treated like a Wye Level. The collars 
 at the end of the telescope barrel serve to adjust the cross-wires for collimation by revol- 
 ving the telescope in wyes. When this is accomplished the telescope barrel with its attached 
 level is then firmly screwed to the cross-bar. The next step in the shop is to adjust the spirit- 
 level to the line of collimation as described elsewhere. This being done, the adjuster 
 in the shop now proves whether the geometric and optical axes of the telescope are really 
 in the horizontal plane by revolving the instrument 180 on its center; should the bubble 
 remain in the middle of its tube it must be assumed that it is; however, if not, he touches 
 one of the uprights off until it does. As a rule the mechanical work is so correct that 
 the geometric and optic axes coincide within a few division marks of the graduated level, 
 requiring but a very few strokes with a fine file for final adjustment. 
 
 From the foregoing it will be seen that a leveling instrument so constructed, barring 
 severe accidents, must hold its adjustments for years, and that all subsequent verifications 
 of the line of collimation in the field by the two peg method must be made by the Engi- 
 neer by slightly moving the cross-wires, and that the adjustment of the spirit-level is 
 to be made in the customary manner by simply turning the instrument 180 on its center. 
 An instrument so constructed needs but little care and therefore is better adapted to 
 rough usage (to which it is subject at times) since its simplicity ensures greater free- 
 dom from derangement. 
 
 The Dumpy Level described above must stand as an example of good practice. 
 Many Engineers prefer it to an ordinary Wye Level. The prevailing mistrust can 
 generally be traced to the use of cheap commercial Dumpy Levels. The above infor- 
 mation as to the method of construction in the shop has been given at great detail tr eho\v 
 that this instrument may well rank with the best wye levels. 
 
 (For Price of this Instrument and Extras see page 126.) 
 
 Berber's Collapsible Dust Guard 
 
 This feature as shown below is furnished with the 14, lo and 1 7>2 inch 3Ioiiitor 
 Type Dumpy Levels and protects the telescope's focussing slides almost com- 
 pletely from grit and water within their entire range. 
 
 TELESCOPE BARREL- 
 
 C.L.BE.RGERiSON3 BOSTON MA5S.U.5.A. 
 
 EXTENDED 
 
 CONTRACTED 
 
129 
 
 C. L,. BEIIGKR & SONS, 
 
 Code AVorcls for Dumpy Levels. 
 
 -inch erecting telescope 
 
 -inch erecting telescope with fixed stadia wires . 
 
 Aciiia 
 Actus 
 
 (For Extras and changes from Acnia and Actus see page B of complete code at back.) 
 
18 
 
 130 
 
 The Berger 
 MONITOR TYPE WYE LEVEL. 
 
 A combination of our Dumpy and Wye Levels, see pages 12&-135. 
 For close bench leveling and construction work 
 whether used on the surface or underground. 
 
 Essential features :- Compactness with great strength as exemplified in our 
 Dumpy Level, to resist severe treatment in rough country work. Protection of 
 spirit-level and collars, thereby securing increased accuracy, efficiency and 
 greater permanency of adjustment. 
 
 In this new type of instrument the adjustment of the line of collimation of the tele- 
 scope and telescope level is made in the same manner as that in the regular Wye 
 Level, but to prevent the wear on the collars and to secure compactness, it 
 differs from that insofar as the telescope can only be revolved in the wyes about 
 20 to 30 to permit of the lateral adjustment of the spirit-level, so as to reduce the 
 wear on the collars to a minimum. The line of collimation of the telescope needs 
 to be verified only at times by lifting the latter out of its wyes after bi-secting a 
 point and then replacing it with the telescope rotated 180, to have level now up 
 thereby securing the same condition as where the telescope is revolvable in the 
 wyes. It is a well-known fact that the wear on the collars where the telescope is 
 revolvable is often so marked that their equality of diameter and true form can- 
 not be depended on, and therefore, while the instrument apparently is in adjust- 
 ment it may be very much out. The only course left open in such a case is to treat 
 the instrument like a Dumpy level and to adjust the level to the telescope by the 
 two-peg method. 
 
 The Spirit-level guarded by the telescope and by a double casing formed as it were 
 by the protection at the sides raises it to the standard of a glass-protected level 
 vial shown in the Precise Levels described later on, but without the detriment com- 
 mon to the latter devices when films settling on the inaccessible vial and inner 
 surfaces of such a protecting glass cover impair the reading of the bubble. To fully 
 protect this level vial from sun and rain at times, or in underground work from 
 smoke and gases a thin piece of transparent celluloid over the exposed part of the 
 vial and held in place by the sides of the cross-bar, will accomplish the same end, 
 and it can be cleaned and renewed at will, thus securing to this instrument and its 
 spirit-level all the advantages possessed by our precise levels, at a very low cost. 
 Size, power and all other particulars are like those of our regular 18" Engineer's 
 Wye Level, page 134, but it is almost entirely finished in our superior and dura- 
 able leather finish, securing permanency of adjustment and presenting a very fine 
 external appearance. 
 
 SPECIFICATIONS : 
 Telescope. Objects erect, aperture 1 ^ inch, power 35 dia. Focussing slide, 
 
 very long and fully protected by dust guard. Collars hard bell metal. 
 Eye-piece with large flat field of view, provided with an improved screw arrange- 
 ment permitting to focus the wires by simply turning its head slightly to right or 
 left. Line of collimation correct for all distances. Telescope balanced each 
 way from center when focussed for a mean distance with sunshade attached, to 
 secure highest accuracy attainable. Stop provided so that the cross wires will 
 always be horizontal and vertical in instrument. 
 Spir it-Level 8fi inch (between centers of supporting arms) level vial accurately 
 
 ground to a true curvature and barrel shape. 
 
 Center hard bell metal (very large in dia. and long, strong and unyielding). 
 Mahogany box provided with strap, lock, and hooks, contains sunshade, wrench, 
 screwdriver and adjusting pin. 
 
 Weight of instrument 11 Ibs. Weight of tripod about 10 Ibs. 
 Gross weight, securely packed for shipment in two boxes, about 55 Ibs. 
 
 Code word, Acway Price, as above, 14O.OO 
 
 Extras to Monitor Type Wye Levels. 
 
 Steel center running in a socket of cast iron, to insure freest motion with perfect fit S15.0O 
 
 Stadia wires, fixed 3.0O 
 
 Short focus lens (see pages 101, 203), one $8.50 . . . per pair 16.00 
 Fine mirror with universal joint readily attachable to either side of the 
 
 instrument, facilitating the reading of the bubble without stepping aside 10.00 
 
 Gossamer water-proof hood, to protect instrument from rain or dust i.oo 
 
 Bottle of fine watch-oil to lubricate the level center .3* 
 
 20i 
 
 in 
 
 MONITOR TYPE WYE LEVEL. 
 
 Aperture 1^ inch, Power 38 dia. 
 Code word, Aczell Price, as described above, $145.OO 
 
131 
 C. L. BEKGER & SONS 
 
 ft 
 
 I I 
 
 Code Words for Monitor Type Wye Levels 
 
 18 inch erecting telescope enumerated page 130 Ac way 
 
 inch erecting telescope Aczell 
 
18 1 
 
 132 
 C. I*. BERGER & SONS, BOSTON 
 
 MONITOR TYPE WYE LEVEL. 
 
 Tubular Bar 
 
 The correct alignments and the handy arrangement of all operating parts make 
 this type of level a profitable investment in any Engineering Department. Designed, 
 built and inspected with typical Berger thoroughness, it can be depended upon to 
 produce accurate work through years of constant service. 
 
 A close inspection of the illustration will reveal a Wye level of a different de- 
 sign embodying many of the features of our standard types. The telescope is sup- 
 ported most rigidly in the two Wyes, which are mounted unusually low on a Bar 
 which is Tubular in form and practically " flexture resisting'." This form of Bar 
 
 permits an entire Rotation of the telescope in its Wyes as in our Engineers 18* and 14" 
 
 Wye Levels, Pages 134135. Owing to its peculiar construction the clamp and a good 
 part of the spindle and its socket are concealed within this Bar which not Only pro- 
 tects these parts from serious injury but keeps out grit and other foreign matter. 
 This instrument has been reduced in height noticeably which gives it an appearance 
 
 Of great Compactness. The Bar is designed so that air-currents which are constantly 
 changing in temperature may pass freely through the top and around the Bar. All this 
 has been done without changing the original length of the spindle which has iden- 
 tified all Berger instruments since 1871, for their wonderful steadiness and freedom 
 from tremor in a high wind. 
 
 The levelling socket is very different in design and a vast improvement over 
 Other makes. It consists of a single piece casting of most peculiar form. The cen- 
 ter will not bind in the socket from any strain exerted either by the spindle clamp 
 or leveling screws. When instrument is clamped the telescope and its level remain 
 absolutely undisturbed owing to its Construction there being a very deep recess 
 
 between the center's socket and the bearing for the center's clamp. This feature is 
 now in universal use on our levels. 
 
 The telescope level is close to the line of coiiimation. The eye-piece and object 
 slides are dust protected by guards. The cap of the eye-piece is large in diameter 
 to protect the observer's eye from the sun. 
 
 The principal parts are treated with our wear resisting leather finish (see 
 
 page 9) which secures a lasting covering to a field instrument and for fine appear- 
 ance has no equal. This finish introduced by us in 1907 is in universal favor. 
 Some small parts are still lacquered which enhance and bring out more forcibly the 
 
 beauty of its constructional lines. 
 
 SPECIFICATIONS: 
 
 Telescope. Objects erect, aperture 1 ^ inch, power 35 dia. Focussing slide, 
 
 very long and fully protected by dust guard. Collars hard bell metal. 
 Eye-piece with large flat field of view, provided with an improved screw arrange- 
 ment permitting to focus the wires by simply turning its head slightly to right or 
 left. Line of coiiimation correct for all distances. Telescope balanced each 
 way from center when f ocussed for a mean distance with sunshade attached, to 
 secure highest accuracy attainable. Stop provided so that the cross wires will 
 always be horizontal and vertical in instrument. 
 Spirit-Level 8^8 inch (between centers of supporting arms) level vial accurately 
 
 ground to a true curvature and barrel shape. 
 
 Center hard bell metal (very large in dia. and long, strong and unyielding). 
 Clamp and Tangent Screw. 
 
 Mahogany box provided with strap, lock, and hooks, contains sunshade, wrench, 
 
 screwdriver and adjusting pin. 
 
 Weight of instrument 11 Ibs. Weight of tripod about 10 Ibs. 
 
 Gross weight, securely packed for shipment in two boxes, about 56 Ibs. 
 
 Code word, Adacta Price, as above, 14O.OO 
 
 Extras to Monitor Type Wye Levels. 
 
 Steel center running in a socket of cast iron, to insure freest motion with perfect fit Slo.OO 
 
 Stadia wires, fixed 3 - 
 
 Short focus lens (see pages 101, 203), one $8.50 . . . pair 16.OO 
 Fine mirror with universal joint readily attachable to either side of the 
 
 instrument, facilitating the reading of the bubble without stepping aside 10.00 
 
 Gossamer water-proof hood, to protect instrument from rain or dust l.oo 
 
 Bottle of fine watch-oil to lubricate the level center ..... .35 
 
 201 
 
 MONITOR TYPE WYE LEVEL. 
 
 Aperture 1> inch, Power 38 dia. 
 Code word, Adulom Price, as described above, $145.OO 
 
133 
 
 C. I* BEHGKK & SONS. BOSTON 
 
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 Code Words for Monitor Type Wye levels 
 
 18 inch erecting telescope enumerated page 132 .... 
 
 Adacta 
 
 inch erecting telescope .... e .... AclllloUl 
 
18 
 
 134 
 
 II 
 
 ENGINEERS' WYE LEVEL. 
 
 leveling Instrument of Precision. 
 For Fine Bench Leveling, Water-works, Railroad Construction, etc. 
 
 Instrument has the strong, liollow and long" cross-bar, introduced by us in 
 1871, mounted upon which are the wyes supported by adjust ing nuts of large diameter, 
 which, together with the long" center also of larjre diameter, gives the necessary 
 stability to withstand rough treatment. To secure compactness the telescope and 
 level tube are close together (to protect latter from sun and rain), and, as both are 
 close to the cross-bar, the instrument is steady in a strong wind. To ensure perma- 
 nency of adjustment, the telescope and level mounting tube have our leather finish (see 
 page 11), which treatment enables us to combine many parts into one, that would have 
 to be screwed together, thereby securing not only great rigidity, but reducing to a min- 
 imum the effect of sudden changes of temperature, and affording, a degree of satis- 
 faction in the field, secured in no other way. This finish presents a fine appearance and 
 is more durable than a metal finish. As much depends upon the sensitiveness of the 
 spirit level we select this for the character of the field work, and, therefore, it ranges 
 in value in this style of instrument from 10 to 20 seconds of arc to one tenth of one inch 
 of scale. 
 
 SPECIFICATIONS: 
 
 Telescope. Objects erect, aperture 1 3/ 8 inch, power 35 dia. Focussing slide* 
 very long and protected by dust guard. Collars hard bell metal and of large 
 diameter. 
 
 Eye-piece with large flat field of view, provided with an improved screw arrange- 
 ment permitting to focus the wires by simply turning its head slightly to right or 
 left. Line of collimation correct for all distances. Telescope balanced each 
 way from center when focussed for a mean distance with sunshade attached, to 
 secure highest accuracy attainable. Stop provided so that the cross wires will 
 always be horizontal and vertical in instrument. 
 Spirit- Level 8)6 inch (between centers of supporting arms) level vial accurately 
 
 ground to a true curvature and barrel shape. 
 Center liard bell metal (very large in dia. and long, strong and unyielding). 
 
 Mahogany box, provided with strap, lock, and hooks, contains sunshade, wrench, 
 
 screwdriver and adjusting pin. 
 
 Weight of instrument, 11 Ibs. Weight of tripod, about 10 Ibs. 
 
 Gross weight, securely packed for shipment in two boxes, about 55 Ibs. 
 
 Code word Adlumia. Price, as above, $ 14O.OO 
 
 Extras to Engineers' 18" Wye Level. 
 
 Steel center running in a socket of cast iron, to insure freest motion with 
 
 perfect fit. (See cut on opposite page). ...... 815.00 
 
 Stadia wires, fixed . ........ 3.OO 
 
 Short focus lens (see pages 101, 203), one $8.50 . . . .pair IG.OO 
 
 Fine mirror with universal joint readily attachable to either side of the 
 
 instrument, facilitating the reading of the bubble without stepping aside 10.00 
 TCxtra sunshade with smaller aperture, for use with the 18-inch wye level 
 
 when the sun's rays are too bright for accurate work .... 1.50 
 
 Gossamer water-proof hood to protect instrument from rain or dust . . l.oo 
 
 Bottle fine watch oil, to lubricate the level center . . . . . .35 
 
 14 
 
 ENGINEERS' WYE LEVEL. 
 
 Its essential features are like those enumerated above, and shown in cut of eigh- 
 teen-inch Engineers' Wye Level, with the exception of size and weight. It is de- 
 signed for use where a lighter instrument is desirable. The Telescope has an 
 aperture of 1 % inches and a power of 27 diameter. The 5^ inch spirit level 
 is very sensitive. The center is of bell metal. Full length, split-leg tripod. 
 Weight of instrument, about 9^ Ibs; weight of tripod, 5^ Ibs. 
 Gross weight of instrument, packed securely for shipment in two boxes, about 40 Ibs. 
 
 Code word Alyssum. Price, as above $13O.OO 
 
135 
 
 Oode Words for Wye levels. 
 18 inch erecting telescope enumerated page 134 (^usual style) Adlumia 
 
 U inch erecting teiescope AlySSUHl 
 
 (For I'J.xtras and changes from Artlmnin ana Aiy8un. see page B of complete code at back.) 
 
136 
 
 18" HYDROGRAPHER'S WYE LEVEL 
 
 Having a three-screw* leveling base with arms of greater radius* * 
 (3-inch) to afford maximum stability when exposed to wind pres- 
 sure and to better control the spirit level of this instrument. 
 
 The instrument shown on opposite page has the upper part, viz: cross-bar, telescope 
 and level exactly similar in size and style to our regular Engineers' 18" Wye 
 
 Level (page 134) except the telescope which in this instrument is mostly of the inverting 
 kind. If an erecting telescope is desired we will be pleased to furnish it, in which 
 case the aperture will be the same but the power will be 35 dia. only. As regards the 
 mode of securing the instrument to the tripod by means of the fastener, see cut and de- 
 scription, page 46, in article, "Shifting Center." 
 
 This fastener is very simple and even in the coldest weather easy to manipulate. 
 It adds very little to the weight and secures the necessary stability in taking up all 
 back lash of the leveling screws after wear. It is better than any other device 
 that we know of to achieve this end. 
 
 The tripod bolts are the same distance' from the center as the leveling screws. 
 
 Made to order only 
 
 SPECIFICATIONS: 
 
 Telescope; objects inverted, aperture 1 3/ inch, power 40 dia.; focussing slide 
 
 very long and protected by dust guard; collars hard bell metal; line of collima- 
 tion correct for all distances; telescope balanced each way from center when 
 focussed for a mean distance with sunshade attached to secure highest accuracy 
 attainable; stop provided so that the cross wires will always be horizontal and 
 vertical in instrument. 
 
 Eye-piece perfectly achromatic with large, flat field of view; provided with 
 an improved screw arrangement permitting to focus the wires by simply turn- 
 ing its head to right or left. 
 
 Center of hard bell metal is large in dia., long, strong and unyielding. 
 
 Spirit Level 8^/3 inches between centers of suspending arms. Sensitive ness is 
 8 to 1O seconds of arc for one tenth inch of the scale, (unless otherwise spec- 
 ified). 
 
 Mahogany box provided with strap, lock and hooks, contains sunshade, wrench, 
 screwdriver and set of adjusting pins. 
 
 Weight of instrument about 12 Ibs. Weight of split-leg tripod about ] 3 Ibs. 
 Gross Weight securely packed for shipment in two boxes about 60 Ibs. 
 
 Code name Andromeda Price as above $158.OO 
 
 Extras to Hydrographer's Wye Level. 
 
 Stadia wires fixed ........... $3.00 
 
 Steel Center running in a cast iron socket to insure freest motion with per- 
 fect fit 15.OO 
 
 Fine mirror mounted in metal frame with universal joint. (This is readily 
 attachable to either side of the instrument and facilitates the reading of 
 the bubble on soft ground without stepping aside). ..... 10.00 
 
 Extra sunshade with smaller aperture for use with the telescope when the 
 
 sun's rays are too bright for accurate work ...... 1.50 
 
 Gossamer water-proof bag, to protect the instrument in case of rain or 
 
 dust i.oo 
 
 Bottle of fine oil to lubricate the level center 0.35 
 
 Prior to 1888 we have sometimes placed upon this instrument an adjustable wye 
 
 with a micrometer screw arrangement for the pointing of the telescope and setting of the bubble 
 independently of the leveling screws. The very marked wear on the collars at the point of 
 contact in the wyes when the telescope is moved in altitude has induced us to abandon this feature. 
 A perfect instrument in this line and at the same time entirely free from any change in height when 
 the micrometer screw is extensively used during an extended leveling operation is our Engineers' 
 Precise Level, page 139. This latter instrument is capable of the most precise work and is offered 
 at a price so very low that it should be included in the instrument equipment for precise leveling 
 of any magnitude. 
 
 To prevent a change of height, after an appropriate leveling of an instrument with three 
 leveling screws, it is advisable to clamp one of the leveling screws by its clamp screw at the side, 
 and to level up by the other two screws alone. This should be done in like manner, also, to correct 
 for slight changes in the level caused by the settling of the tripod-legs. 
 
 * Four leveling screws commend themselves in the more ordinary class of instruments for 
 the greater rapidity with which an instrument can be leveled up approximately, and that (no mat- 
 ter how much the leveling screws may be worn) when brought to a true bearing on the lower level- 
 ing plate, all such looseness is taken up. 
 
 **NOTE: In some types of leveling instruments numnted on a three-screw leveling base the 
 latter is often too small for the length, power, height and weight of the instrument, making it top 
 heavy, thereby rendering it unsteady and unsuitable for close work. 
 
137 
 C. L. BEKGEB & SONS. 
 
 3 
 
 S3- 
 
 Code Word Andromeda. 
 
138 
 
 Reversion Level. 
 
 Applicable to any of our Engineers' Wye Levels* 
 
 The spirit level used in this feature differs from the ordinary one in that it is 
 ground to the true shape of a barrel so that the tangents to the level bubble curves, at the 
 zero points of the scales, are parallel and diametrically opposite. By the use ot : this rever- 
 sion level, attachable to any of our Engineers' Wye Levels, in place of the single read- 
 ing level, it is possible to do good leveling, though the adjustments of the spirit level 
 and cross wires are entirely deranged and the collars worn (see remark below), by first 
 making the level bubble central and taking a reading, then by revolving the telescope 
 180 in its wyes, which point is indicated by an adjustable stop,* making the bubble 
 again central and taking- another reading. The arithmetical mean is the correct result. 
 
 This device will, in an emergency, be appreciated when it is known that by the use 
 of the method above the work will average a^ good as that done with an ordinary good 
 wye level, in adjustment. The adjustment of an instrument provided with a reversion 
 level is made in precisely the same manner as if the spirit level was of the single read- 
 ing kind, since the adjustment of the level when it is reversed will take care of itself. 
 
 The reversion level is guarded by a revolvable outnr tube (Patented, not shown in 
 cut) leaving a space of air, as a non-conductor of heat between it and the ordinary level 
 mounting tube. This exterior tube serves both as a protection against breakage and 
 sudden changes of temperature, and, as its inner surface is painted white, it also acts 
 as a reflector which facilitates the reading of the bubble. 
 
 IJemark: The inequality of worn collars cannot be eliminated in a strict sense 
 by using the reversion level, yet for ordinary good work it may be said to be. Nor can 
 the test for the equality of the collars be directly tested in this way but should be done 
 as in the case of the ordinary wye level ; viz , by the two-peg method described under 
 the adjustment of the Dumpy Level (pages 63 and 64 of our handbook). The follow- 
 ing modification is to be noted: After the line of collimation has been adjusted for dis- 
 tant objects by rotating the telescope in its wyes and the spirit level has been adjusted 
 by reversing end for end and adjusted laterally, (the telescope having the sunshade at- 
 tached, as it serves to balance the telescope when the object slide is drawn in), the in- 
 strument is set up close to the near target, and a reading is taken with the level tube 
 in the direct position. In order to eliminate the error of collimation for nearer objects, 
 should any exist, another reading is taken with the telescope rotated 180 in the wyes, 
 and the mean taken as the true reading. If, now, the horizontal wire also bisects the 
 distant target and the bubble remains central in each position of the telescope, the 
 collars are of equal diameter. Should the latter not be the case, the error may be cor- 
 rected thus : Bisect the distant target with the telescope in its direct position, and adjust 
 the level till the bubble is central. Rotate the telescope 180 in its wyes, indicated by 
 the stop, and note the number of divisions through which the bubble moves in order 
 that the distant target remains bisected, so that a correction can be made when most 
 precise work is required. 
 
 It is assumed that in making this test the temperature of the two collars has been 
 alike and that the telescope has been in proper balance by being focussed for a distance 
 of about 300 feet with sunshade attached. A scratch on the telescope or object slide 
 indicates the focus which the maker used in equalizing the collars. An apparent error 
 found as above may be due to a change in the shape of the level tube which may occur 
 in time (for which the maker, of course, cannot be held responsible), as well as to a 
 worn condition of collars, or these causes combined. 
 
 In order to trace the error to its source the only sure test is made with a striding 
 level. (See Engineer's Precise Level.) 
 
 Price, as above, if ordered with our Wye Level in place of the single reading 
 kind .'.../ $20.00. 
 
 Y It is an extremely difficult matter to glint 5 a level of this kind so that the bubble will remain central at 
 all positions during this rotation through 180. The stop just mentioned is so adjusted, however, by the maker, 
 that when the level has been turned exactly 180 it gives a correct reading. 
 
139 
 
 C L. BERGER & SONS' ENGINEERS' PRECISE LEVEL. 
 
 Patented. {For cut see page 141.} 
 
 With micrometer screw for close setting the spirit level. 
 
 For use in cities in establishing benches, etc., also for all work requiring speed and the highest 
 degree of accuracy in spirit leveling. 
 
 It is a well-known fact that, satisfactory as it may be on account of its great sim- 
 plicity and compactness, the ordinary wye level (pp. 134, 135) will fail in degree of ac- 
 curacy or in rapidity of manipulation when the closest results are required. It often 
 happens when precise work is required, the time spent in leveling up and keeping the 
 level bubble of an ordinary good wye level in the center of its graduation by means of 
 the four leveling screws is often very considerable and, when the course is over 
 swampy or frozen ground, the vexation attending the work is apt to be great, and the 
 results vitiated by the numerous readjustments required to keep the bubble in its 
 place. This manipulating of the leveling screws is very apt to lead to a change in the 
 height of the telescope, varying in magnitude according to the style of the instrument. 
 (It is here to be noted that this change in the height of the telescope is less in our 
 levels, or transits with leveling attachments, than is the case with the instruments 
 of other makes). 
 
 To aid the Engineer in the prosecution of exact work, avoiding the errors caused 
 by the readjustments above referred to, we have designed and are prepared to furnish 
 the instrument shown on page 141. 
 
 By referring to the cuts it will be seen that this instrument is mounted on three 
 leveling screws, and that the center about which the instrument revolves is unusually 
 long and unyielding. Two small spirit levels attached to arms extending from what 
 we may call the cross-bar (since the center of the instrument is permanently secured 
 to it as in the ordinary style of levels) serve to put the center in a vertical position, 
 thus securing at once a nearly horizontal position to the cross-bar. These small levels 
 are adjusted the same as the ordinary piaie levels of a transit. 
 
 At the eye end this cross-bar carries a micrometer screw by which the telescope 
 and its level can be raised or lowered at will independently of the leveling screws. A 
 strong spiral spring on the same side holds the wye-bar down upon the micrometer 
 screw. This arrangement provides a most delicate motion up and down, and enables 
 one to set the bubble accurately at every sight and in a very much better manner than 
 can be done by the leveling screws alone. The head of the micrometer screws is di- 
 vided into one hundred parts, and as a rule its pitch will be such that 250 to 252 parts 
 of revolution of the screw will make a change of one foot in the reading of the rod held 
 at a point 100 feet away from the center of the instrument. It may be seen that the 
 instrument can be very advantageously used for making grade measurements. The 
 graduated disc, when reading zero on the index-bar, brings the instrument at once 
 within one or two divisions of its normal position. The di-c can also be readily turned 
 on its hub by taking hold of the mille'l head (the disc is held on its arbor simply by 
 friction), so that, for convenience, a reading may always start from zero, though the 
 cross-bar be not leveled up. This instrument, as above stated, is provided with three 
 leveling screws, which give a firm support on the tripod, and allow a closer setting of 
 the bubble when the instrument is run as an ordinary wye level, without making use 
 of the micrometer. (Seep. 44.) 
 
 The Chief Feature of the Instrument, however, consists in the fact that the 
 pivots * ou which the wye bar can be raised or lowered, are in the middle of the instru- 
 ment and within a fraction of an inch of the plane of the line of collimation, thus se- 
 curing to the telescope a motion in altitude free from any change in height of the line 
 of collimation, though the telescope were to move throughout the entire range of the 
 micrometer screw during an extended leveling operation. As 9 rule, the working range 
 of the micrometer will be limited to a few revolutions each way from its normal posi- 
 tion in order to keep the instrument as compact as possible. The instrument is also 
 arranged so that, whenever desirable, it may be used as an ordinary wye level. For 
 this purpose, it is provided, at the object end of the cross-bar, opposite the micrometer 
 screw, with a milled-head screw and check nut, by means of which, and by the micro- 
 meter screw, whep set at zero (see cul), the wye bar may be set exactly at right angles 
 to the vertical center. However, for the fine settings of the bubble in bench leveling 
 or pointing of the telescope, etc., the micrometer screw should be used exclusively. 
 
 A clamp and tangent screw motion is also provided and so arranged, that it can 
 be readily reached from the eye end of the telescope. The cross and wye-bars are 
 cast hollow and the former fits inside the latter. 
 
 *NOTE. It will be noticed that in instruments of a similar character, having pivot screws acting in and below 
 the wye opposite the micrometer screw, as for instance, in the TJ. S Coast Survey geoaesic leveiSj designed 
 after Stampfer (see Reoort 1879), any motion ot the telescope in altitude will also change its height. By an 
 injudicious use of the micrometer screw our own hvdrographic wye level (see page 1043, catalogues 1888-1891). 
 partook of this same error, and this together with the marked wear on the collars due to this same motion led 
 us to the abandonment of it. We note, however, that other firms who are in the habit of copyh^'our style* 
 aed patterns have since brought it out as a detail of a precise level. 
 
140 
 
 The Telescope will be invariably inverting in order to admit of as large an aperture and as high a powei 
 as is possible. Thus : its aperture will be i J inches, the total length is about 17 inches, and it will have a 
 magnifying power of 40 diameters. It will be provided with fixed stadia wires, in the proportion of i to 100, 
 the distance to be measured Irom a point in front of the objective equal to its focal length 
 
 The Spirit Level is of the single reading kind, and is generally made so that one division (of -rV of an 
 inch) equals from 8 to 10 seconds of arc. The sensitiveness of the level will, however, be adapted to the par- 
 ticular requirements. It is not necessary, however, to have it any more sensitive than is required for a fine 
 field instrument, as an over-sensitive level is apt to give more trouble than benefit in its use. 
 
 A Reversion Level of same sensitiveness might be applied instead of the single reading level, if desired, 
 as a convenience (see Reversion Level p. 136), when the highest precision is not needed. Of course in fine work 
 the reversion level must be used in the direct position as with a single reading level. However, one will un- 
 derstand that a reversion level is very apt to change its true barrel form in time thus becoming wholly 
 unreliable, and therefore we do not advise it at all, and particularly not for an instrument of such a fine 
 character as this is. 
 
 A Metal Mirror will be furnished with the instrument, attachable to either side of the level, enabling the 
 operator to read the bubble without stepping aside ; a convenience which will be appreciated when working on 
 shaky ground. 
 
 Adjustment. The adjustment of the telescope and the level must be made precisely as in an ordinary 
 wye level. (See adjustment of the wye level, pages 59 and 63 of this hand-book ) The spirit level will be in 
 thorough adjustment when the telescope with its sunshade attached is focussedfor a distance of about 400 feet, 
 when the telescope is in perfect balance and the equality of the collars is assured thereby ; for shorter distances, 
 however, there is a small error due to the unbalancing of the telescope caused by the object slide being thrown 
 out. Small as this error may be it can be entirely eliminated by simply bringing the bubble to the center by 
 the use of the micrometer screw. 
 
 Explanation. The foregoing has been written at some length to give a clear understanding of the prin- 
 cipal features of this instrument. Naturally, the question may now present itself, why not use a striding level 
 alone, in place of the fixed or reversion level, as is done in some of the best types of instruments, particularly 
 as the pivot arms, extending from the middle of the cross-bars, must necessarily be spread quite a distance 
 apart, to readily permit the revolution of the telescope with the fixed level in the wyes. To this we may say, 
 that a fixed level placed below the telescope, where it is guarded against breakage and, in a measure, from the 
 action of the sun, is better adapted to the wants of the Civil Engineer in running quick and accurate levels 
 in cities, towns, etc., than a striding level with its more cumbersome features and manipulations would be, 
 particularly if the work was to be of the most precise character. 
 
 It is only when the collars of a telescope are badly worn or imperfectly made that the striding level has 
 any advantage over a fixed one. As a rule a fixed level keeps in better adjustment, is simpler to manipulate 
 than the striding level, and is free from the errors due to the uncertainty of contact of the collars and the wyes. 
 Moreover, the construction of the new instrument is such that it has a greater stability than those of previous 
 make. We therefore believe that the fixed level has as legitimate a standing as the striding one. 
 
 For the above and similar reasons the American Engineers have and will give preference to the instru 
 ment which has the level fixed to the telescope; and this has led us to the adoption of this feature in our new 
 instruments. This idea is also prevalent among the best instrument makers and engineers in Europe, as may 
 be seen by examining Prof. Nagel's published description of a similar instrument. 
 
 Instrument, Finish, Packing*, Weight, etc. The telescope is leather-finish, 
 while some of the more bulky parts of the instrument are simply treated either with 
 cloth finish or japan, in order to lessen the cost No attempt will be made to give an 
 elaborate finish at the expense of accuracy and utility ; altogether, as all the other 
 parts will be bronzed and lacquered in a manner customary with us, it will present a 
 handsome appearance. This instrument is packed erect in one box in the same man- 
 ner as we pack the regular engineer's wye level. It is secured to the tripod in the 
 same manner as are all of our instruments with three leveling screws. (See page 136 
 for description ) 
 
 The mahogany box contains a sunshade, wrench, screw-driver and adjusting pin. 
 
 Weight of instrument, !!- pounds; weight of tripod, 10-J pounds; weight of ma- 
 hogany box, 10| pounds ; gross weight of instrument complete, securely packed in two 
 boxes for shipment, 60 Ibs. 
 Price of this instrument, inverting telescope, leather-finish, fine 
 
 mirror mounted in case, fixed stadia wires, and a single reading fixed 
 
 spirit-level, ... $215.OO 
 
 Extras to Engineers' Precise Level 
 
 Center of instrument made of steel, and hardened and running in a socket of 
 
 cast iron, improved style (see cut, page 135), .... 15.00 
 
 Sunshade with smaller aperture, for use with the telescope when the sun 
 
 rays are too bright for accurate work, 1.00 
 
 Gossamer bag, to protect instrument. .... ... 1.00 
 
 Bottle of fine watch oil for lubricating the centers, etc., 0.35 
 
 t If geodesic work is to be done, 
 
 , higher sensibility might be permissable, but our customary fluid would be sluggish in 
 ave to be filler! with pure ether, in order to make it quick acting (see pages 7, *8, 38). 
 
 , 
 
 An air chamber would be necessary to allow for adjustment of the bubble, which in this case changes its length rapidly for 
 perature. By adding a chamber, a feature is introduced which is liable to affect the reliability of th 
 
 sltehr changes in temperature. By adding 
 Spirit level and entail extra expense 
 
 Code Word. Engineers' Precise Levi bnt witn steel centre Arethusa 
 
141 
 
 H 
 
 3 
 M 
 
142 
 
 THE GEODETIC LEVEL. 
 
 In response to a request of President T. C. Mendenhall to construct ir the 
 Worcester Polytechnic Institute a Precise Wye Level, the senior member of this firm 
 in 1896 designed and made the type shown on next page. 
 
 The leading features are great compactness, rigidity, simplicity of design, ease of 
 manipulation, and thorough adaptation of every part to its purpose. In order to lessen 
 the height above the tripod, the weight of the instrument and the surfaces exposed to 
 wind pressure, this particular form of cradle bar has been adopted ; and, while this 
 reduction might have been carried to a greater extent by placing tae vertical revolving 
 center inside the tripod head, it was thought not advisable, as sometimes it is desirable 
 to set the instrument on the leveling screws when detached from the tripod. 
 
 As will be seen, the improved tripod is of a very stiff form, which is necessary 
 where telescopes of great power and highly sensitive spirit levels are used. To eliminate 
 the effect of unequal expansion, the telescope collars are of smallest possible diameter 
 compatible with the diameter of the object glass, and at first were of hardened steel 
 resting on agates at point of contact in wyes. The striding level adopted in place of 
 the fixed level is of tubular form and has very short legs. To still further reduce the 
 effect of unequal expansion, the substructure, such as cradle bar, fixed bar and other 
 parts, below the agates at point of contact in wyes in this instrument, consisted of steel 
 and iron. Subsequently, however, as the danger of rusting in the field became very 
 apparent, the use of steel and iron was not thought to be as important in portable field 
 instruments when used on tripods as in the stationary astronomical instruments : there- 
 fore we are making the substructure of our customary hard gun-metal, and shall so 
 furnish them, unless ordered to be of steel, in which ca.se the instrument will have to 
 be specially made. (See below.) The same may be said of the hardened steel collars. 
 Unless ordered otherwise the collars will be made of hardest bell-metal. 
 
 All the parts that must be handled during a field operation are protected by a 
 shield of a non-heat-conducting material. By means of a micrometer screw the telescope 
 can be moved in the vertical plane around the center in the middle of the instrument 
 in order not to disturb the height of the intrament. 
 
 The striding level has a bubble tube reading to 3'' of arc and is provided with an 
 air chamber. Mounted above it is a mirror to enable the observer to read the bubble 
 without stepping aside. Provision is made to readily lock the striding level to the 
 cradle bar, to enable one to use the instrument like an ordinary Wye Level (with level 
 fixed to the telescope) ; and to carry the instrument on its tripod from station to station. 
 An arrangement is also provided by which the striding level upon reversing will always 
 find its proper plane on the collars, so as to require but very little attention on the part 
 of the operator. By means of a clamp screw opposite the micrometer screw the cradle 
 bar can be secured so that the instruments can be used for ordinary wye level work. 
 
 Two auxiliary levels placed at right angles serve to level up approximately ; after 
 which the final setting of the striding level is done by the micrometer screw attached 
 to the fixed bar. The vertical center is of hardened steel and runs in a socket of cast 
 iron. All the main parts are either cloth finished or japanned. The beautiful appear- 
 ance of the instrument does not depend upon the external finishing and polishing of 
 parts, but entirely upon the harmony, simplicity and excellence with which the essential 
 features of the instrument are designed. 
 
 For a detailed description of the instrument we refer to a paper read by Mr. David 
 Molitor before the Am. Soc. of C. E. (See Proceedings 1899-1900.) 
 
 The telescope is inverting, with an object glass of 1^"? focal length of 17", 
 and a power of 40 diameters. It is provided with the usual cross and stadia wires. 
 Instrument packs in pine wood box, which contains a sunshade, screw driver, adjusting 
 pin and gossamer bag. 
 
 Weight of instrument ....... 14 Ibs. 
 
 Weight of tripod 15 Ibs. 
 
 Gross weight of instrument packed securely for shipment in two boxes 75 Ibs. 
 
 Price as above, of brass and bell metal collars, . . ... $280.00 
 Price of instrument, substructure of steel, as above, extra, . . 25.00 
 
 Price of instrument, collars of telescope of hardened steel, extra, . 25.00 
 
 Code Word for Geodetic L,evi of brass and bell metal collars Artemisia 
 
143 
 
 The Berger Geodetic Level. 
 
144 
 
 COAST SURVEY PRECISE LEVEL 
 
 The demand for a level whereby the utmost precision possible in leveling may be ob- 
 tained comes from many sources in work where the absolutely correct determination 
 of the relative height of a line of benches is sought. 
 
 The Coast Survey Precise Level, illustrated by accompanying cuts, is designed to 
 meet this demand ; and it is probably the most perfect instrument made of the dumpy 
 level type. 
 
 The essential feature which gives value to this instrument is the fixed adjustment be- 
 tween the line of collimation and the level by the use of nickel iron, with coefficient of 
 expansion of 0.000004 per degree Centigrade, in combination with nickel steel, with 
 coefficient of expansion of 0.000001 per degree Centigrade ; and the location of the level 
 partially within the telescope and as near as possible to the line of collimation. 
 
 The instrument is so made that the line of collimation is adjusted by the maker once 
 and for all as in our Dumpy Level, by revolving the telescope in auxiliary wyes on 
 rings turned concentric with the bore of the telescope tube. If it becomes necessary 
 to replace broken wires in the field, the reticule must be removed, wires and reticule 
 then replaced in the telescope, and adjusted for collimation by its capstan-headed 
 screws and the two-peg method. This latter operation assumes that the position of 
 the spirit level in relation to the telescope has not been disturbed, and that its adjust- 
 ment is still perfect or nearly so. 
 
 An important feature of the instrument is the prismatic reading attachment for the 
 level bubble, whereby the observer reads with one eye the rod and with the other eye 
 the level simultaneously without change of position. 
 
 With short sights the instrument permits great accuracy and quick action in skilled 
 hands. 
 
 Standing erect, the observer takes the back sight by reading the three horizontal 
 wires on the "self-reading" rod, and then again the middle wire as a check, each of the 
 readings being made with the bubble set to the normal by means of the vertical fine 
 motion screw. Swinging the telescope round to the forward rod, he repeats this pro- 
 cess for the foresight . The records of the Coast and Geodetic Survey show that the time 
 of occupying one station is somewhat less than 5 minutes. In the season of 1911 one 
 of the engineers of the Survey ran 14.35 miles single or 11.547 kilometers completed 
 (back and forth) line in one day of 7 hours 30 minutes actual work. None of this level- 
 ing required re-running, all of it closing within the error of tolerance, i. e., 4 mm -v/K~ 
 in which K stands for the distance expressed in kilometers. 
 
 In constructing this instrument we follow absolutely the Coast Survey specifica- 
 tions, using nickel-iron and nickel-steel as called for, thus insuring a rigid maintenance 
 of the adjustment of instrument under marked changes of temperature. 
 
 This level is guaranteed to pass the Coast Survey's inspection. 
 
 For details of construction and use, see Transactions of the American Society of 
 Civil Engineers, June, 1901, pp. 127-175 ; U. S. Coast and Geodetic Survey Report for 
 1902, Appendix No. 4, and Report for 1900, Appendix No. 6. 
 
 SPECIFICATIONS : 
 
 Telescope, inverting, length 17 inches, aperture 1^", power about 
 
 40 diameters. 
 Level to telescope, length 53^ inches, chambered, graduated in 2 mm 
 
 divisions each sensitive to 2" of arc. 
 Stadia wires, ratio 30 cm to 100 meters. 
 Micrometer screw, 100 revolutions to 1 inch; head divided into 100 parts. 
 
 A cam is provided for lifting telescope from micrometer screw 
 
 when not in use. 
 
 Weight of tripod, about 19 Ibs. ; in packing box about 50 Ibs. 
 Weight of instrument, about 14 Ibs. ; in instrument box about 30 Ibs. 
 Gross weight of level packed securely in two boxes for shipment, about 
 120 Ibs. 
 
 Code word, Aster. Price $375.OO 
 
145 
 C. L,. BEBGEK & SONS. 
 
 o 
 
 o 
 
 I 
 
146 
 
 PLANE TABLE 
 
 This instrument, as shown in cut on opposite page, has been designed to fill a want 
 
 where a high class of work in topography is required. It IS made 1U two sizes. The 
 
 alidade is built strong and light. The ruler is of brass. Other parts are of alumi- 
 num, or brass, as best serving the purpose. The telescope is well lighted, powerful, 
 and of greater length than usual, the latter enabling the observer to readily sight 
 at an object when the alidade is some distance from the edge of the board. The ruler 
 is provided with two fixed levels and is so arranged that lines can be ruled in the 
 vertical plane of the telescope, if desired. 
 
 To obtain great rigidity and strength, the diameter of the bearing surface of the lower 
 motion in both sizes is larger than usual and the board rests on radial arms extending 
 considerably beyond this bearing surface. The tripod head is of corresponding size. 
 To be portable, all the essential parts are built on the skeleton plan. To avoid a loosen- 
 ingof the leveling screw fastenings so often experienced where the latter are fitted 
 into tripod heads made of wood, we make this head of composition brass, or of alu- 
 minum, and to prevent all wabbling of the leveling screws when worn, these latter are 
 also provided with check nuts. Materials and workmanship are of the best. 
 
 SPECIFICATIONS: 
 Alidade. Length of ruler 22 inches. 
 
 Telescope. Inverting. Aperture l^g inches. Length 16 inches. Power 35 dia. 
 
 (For adjusting the line of collimation, the .telescope can be revolved 
 180 on its longitudinal axis. 
 
 Stadia wires. Katio 1 : 100. 
 
 Vertical arc. 4}^ inches, graduated on solid silver, double verniers reading to 
 
 minutes. The vernier arm is provided with a level on top for a 
 ready control of zero of verniers. 
 
 Striding" level. 6 inches over all. 
 Compass needle. 4^ inches. 
 Lower motion, (usual size) with tangent screw (for boards 24 X 30 in. or 22 X 
 
 24 in.) Spread of arms from center 4^ inches. 
 
 Weight of Alidade with brass ruler, .... about 7 Ibs. 
 
 " " Lower motion, usual size, with arms 4^ inches, 
 
 " " Tripod, 
 
 " " Board, 
 
 6f " Alidade and accessories in mahogany box, 
 " " Lower motion in special box, with legs detached, 
 Board in canvas case, 
 
 -9 
 
 15* 
 9 
 
 18 
 15 
 11 
 
 Gross weight of instrument packed in four boxes ready for shipment, 100 
 
 Price of Plane Table as above, and as in cut, including one board 
 24 X 30 inches, detached compass, screw-driver, clamps, reading 
 glass, plumb-bob, (board and tripod packed in pine wood ship- 
 ping cases, alidade with attachments in mahogany box, lower 
 motion in pine wood box) ........ $3OO.OO 
 
 Price of Alidade alone, as above, with striding level, detach- 
 able compass, etc. , in mahogany box, but without board and lower 
 motion and tripod, $2OO.OO 
 
 Price of Interchangeable Micrometer 
 
 Code Word AtluS. Made to order only. $5O.OO 
 
 Price of Canvas Case for board . . . . . $2.OO 
 
 Note : Lower motion as above, but with a bearing surface 8 inches in diameter, 
 having arms extending to 6 in. from the center, can be supplied for regular or larger 
 boards, in place of the one specified above. Weight about 11 Ibs. 
 
 Price extra, $1O.OO 
 
 To meet a want where greater portability and lightness are thought to be more ad- 
 vantageous than greater rigidity and consequent accuracy, we are prepared to furnish 
 in place of the above described lower motion of the Plane Table (shown in the accom- 
 panying cut) one of the Johnson type and character. A description of this may be 
 omitted here, since it is described in any of the modern text-books on Plane Table 
 Work. Suffice it to say that this motion is operated in a manner similar to that de- 
 scribed under our Quick Leveling Attachment (see pages 45 and 118) of which it is an 
 inverted adaptation, but is of greater size, range and steadiness. 
 
 This movement, with legs all complete, weighs only from 9 to 10 Ibs. 
 
 Price of Johnson's Improved Plane Table Movement, 
 
 mounted on large tripod ......... 
 
147 
 
 C. L. BEKGEK & SONS. 
 
61" 
 
 150 
 
 ENGINEERS' AND SURVEYORS' TRANSIT. 
 
 This instrument is designed for engineering work of a high class, such as is required 
 in bridge building, water-works, and for city and land surveying. The size of the cir- 
 cle is such that it may be graduated to read to 30" or 20" without fatigue to the eye. 
 The telescope is of the best definition, and has a large aperture with perfectly flat lield. 
 The eye-piece is achromatic, and gives a large field with plenty of light. We advise 
 our customers to order solid silver graduations for this instrument. Silvered gradua- 
 tions are made to order only, being of rare inquiry. 
 
 Transits size No. 1 No. Ic. 
 
 Specifications : Horizontal Circle 
 
 6 1 4 in. (edge of graduation), double opposite verniers read to minutes, two rows of 
 figures in opposite directions from to 360, figures on limb and verniers inclined in the 
 direction they should be read, verniers protected with fine plate glass, and provided with 
 glass shades, graduations silvered; long compound centers with heavy flanges; 
 edge-bar* magnetic needle 4'^ in.; spring tangent screws; fine telescope 
 11 1^ inches long, objects erect, aperture 1% inches, power of telescope 24 diani. (well 
 adapted for stadia work), eye piece provided with an improved screw arrangement for 
 accurately focussing the cross-wires, telescope perfectly balanced reverses at both ends, 
 line of collimation correct for all distances, protection to object-slide, adjustment for ver- 
 tical plane of telescope ; spirit levels of standard length, ground and extra sensitive ; 
 shifting center to set the instrument exactly over or under a given point ; top of telescope 
 provided with a very fine punch mark to also enable to center the transit from a point 
 above; standards leatherized (see p. 11), full length split-leg tripod, etc. 
 
 The Mahogany Case has a leather strap, hooks, etc., and contains a sun-shade, a 
 wrench, a screw-driver, an adjustable plumb-bob, a magnifying glass, adjusting pin, and 
 weighs from 9^ to 10 Ibs. 
 
 Weight of Plain Transit No. 1 13% Ibs. 
 
 " Transit with Level Attachment (No. la) 14 " 
 " Complete Transit (No. Ib and No. Ic) . 14% " 
 
 Gross Weight of Instrument complete, packed securely for shipment in two boxes, 
 about 60 Ibs. 
 
 Plain Transit, size No. 1, as described above, see cut on opposite page. 
 Code Word, Babelle. Price (graduations silvered), $18O.OO 
 
 Transit NV). la, size, etc., asunder No. 1 above, with long, sensitive lev el, clamp 
 and tangent screw to telescope, see cut page 152. 
 Code Word, Balnode. Price (graduations silvered), $21O.OO 
 
 Transit No. 1 1>, size, etc., as under No. 1 above, but with a level, clamp and 5-inch 
 vertical arc to telescope. Arc has double verniers reading to minutes, see cut page 153. 
 Code Word, Besica. Price (graduations silvered), $225.OO 
 
 Transit No. Ic, size, etc., as under No. 1 above, but with a level, clamp and 
 5-inch full vertical circle to telescope. Vertical circle has double verniers reading to 
 minutes, and is protected by an aluminum guard, as in cut page 154. 
 Code Word, Boscardo. Price (graduations silvered), $237OO 
 
 Extras to Plain Transit No, 1 Transit No. Ic inclusive. 
 
 Standards polished and lacquered (no leather finish), made to order only . $5.00 
 
 Graduation of horizontal circle, on heavy inlaid ring of solid silver . . 10.00 
 
 " reading to 30" ... . 10.00 
 
 " " " " 20" 20.00 
 
 " vertical arc or vertical circle on heavy inlaid ring of solid silver 5.00 
 
 Gradienter attachment (see pp. 6 and 45) . . ' . . . . 5.00 
 
 Stadia Wires, fixed . . . " . . . . . . . . 3.00 
 
 Short Focus Lens (pp. 101, 203). One pair ....... 16.00 
 
 Arrangement for offsetting at right angles . . . . . . 5.00 
 
 Variation plate, adapted for ah declinations E. or W. . . . . . 10.00 
 
 Cravenette hood (heavy, gives good protection); Silk (light, not waterproof) each 1.00 
 
 Bottle of fine watch-oil to lubricate the centers, etc., of transit . . . 0.35 
 
 An Inverting 1 TeleSCOpe of iy&" aperture, \\%" focal length and power of 28 
 <lia. can be supplied with the above transits in place of the regular erecting one at 110 additional 
 cost. This telescope is particularly well adapted for stadia work. The weight is 9 oz. more. This 
 instrument is made to order only. 
 
 * Correct form having no index error. See pages 98, 99. 
 
151 
 
 C. L. BERGKR & SONS. 
 
 K 
 
 No. 1. 
 
 in. at edge of graduation.) 
 
 Plain Transit. 
 
 For size and description of this instrument, as well as for Extras, see opposite page. 
 
 Plain Transit No. 1, as shown above, and as described under Plain Transit No. 1 (Babelle), on 
 opposite page, verniers reading to minutes, but with graduations on solid silver, as usually supplied. 
 
 Code word, Babiana. Price, $19O.OO 
 
 (For code words for Extras and changes from Babiana, see page C of complete code at back.) 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so ordered to be 
 made specially. 
 
 Sketch "A" shows the bearings in the standards for the V-shaped form of the tele- 
 scope's axis, the improved manner of fitting the adjustable "Wye block in the standard 
 by means of dovetails instead of pins, also the adjustment of the block by opposing cap- 
 stan-headed nuts, securing thereby : 
 
 1. Greater rigidity of the bearing block in the standard, resulting in a truer motion of the 
 telescope. 
 
 2. Greater ease of making the vertical plane adjustment, as compared with other makes of the 
 same class. 
 
 3. Greater permanency of this adjustment when made. 
 
152 
 C. L,. BERGER & SONS 
 
 No. 1 a. 
 
 6 1 4 in. at edge of graduation. 
 
 Transit with Level Attachment* to Telescope. 
 
 For size and particulars of this instrument, as well as for Extras, see page ISO. 
 
 Transit No. 1 a, same as shown above, and as described under Transit No. 1 a. 
 (Balnode), page 150, verniers reading to minutes, but with graduations on solid 
 silver and with fixed stadia wires as usually supplied. 
 
 Code Word, Balsam. 
 
 (For code words for Extras and changes from Balsam, 
 see page C of complete code at back.) 
 
 Price, $223.OO 
 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so 
 ordered to be made specially. 
 
 * With a level attachment of the above kind, good leveling can be done, as the power of the telescope and 
 the sensitiveness of the spirit-level are equal to that of most Wye-levels. 
 
153 
 C. L,. KERGER & SONS 
 
 No. 1 b. 
 
 in. at edge of graduation.) 
 
 Complete Engineers' and Surveyors' Transit. 
 
 For size and description of this instrument, as well as for Extras, see page 15O. 
 
 Transit No. 1 b, as shown above, and as described under Transit No. 1 b (Besica), 
 on page 150, verniers reading to minutes, but with graduations on solid silver and 
 with fixed stadia wires as usually supplied. 
 
 Code word, Betonica. 
 
 (For code words for Extras and changes from IJetonica, 
 see pages C, D and F of complete code at back.) 
 
 Price, $243.OO 
 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so 
 ordered to be made specially. 
 
152 
 C. L,. BERGER & SONS 
 
 No. I a. 
 
 T 4 in. at edge of graduation.) 
 
 Transit with Level Attachment* to Telescope. 
 
 For size and particulars of this instrument, as well as for Extras, see page ISO. 
 
 Transit No. 1 a, same as shown above, and as described under Transit No. 1 a. 
 (Balnode), page 150, verniers reading to minutes, but with graduations on solid 
 silver and with fixed stadia wires as usually supplied. 
 
 Code Word, Balsam. Price, $223.OO 
 
 (For code words for Extras and changes from Balsam, 
 see page C of complete code at back.) 
 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so 
 ordered to be made specially. 
 
 * With a level attachment of the above kind, good leveling can be done, as the power of the telescope and 
 the sensitiveness of the spirit-level are equal to that of most Wye-levels. 
 
153 
 C. L. BERGER & SONS 
 
 . 1 b. 
 
 In. at edge of graduation.) 
 
 Complete Engineers' and Surveyors' Transit. 
 
 For size and description of this instrument, as well as for Extras, see page ISO. 
 
 Transit No. 1 b, as shown above, and as described under Transit No. 1 b (Besica), 
 on page 150, verniers reading to minutes, but with graduations on solid silver and 
 with fixed stadia wires as usually supplied. 
 
 Code word, Betonica. 
 
 Price, $243.OO 
 
 (For code words for Extras and changes from lietonica, 
 see pages C, D and F of complete code at back.) 
 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so 
 ordered to be made specially. 
 
154 
 C. L. BERGER & SO>S 
 
 No. 1 c. 
 
 in. at edge of graduation.) 
 
 Patented. 
 
 Complete Engineers' and Surveyors' Transit. 
 
 For size and particulars of this instrument, as well as for Extras, see page 15O. 
 
 Transit No. 1 c, same as shown above, and as described under Transit No. 1 c. 
 (Boscardo), page 150, verniers reading to minutes, but with graduations on solid 
 silver- and with fixed stadia wires, as usually supplied. 
 
 Code word, Bouvarclia. Price, $255.OO 
 
 (For code words for Extras and changes from Bouvardia, 
 see pages C, D and F of complete code at back.) 
 
 The verniers of this instrument can be placed at an angle of 90 to line of sight, if so 
 ordered to be made specially. 
 
155 
 
 Special Vertical Circle. 
 
 A 5 J-Inch Vertical Arc or Full Circle with Hal graduations of style 
 
 shown for No. 1 b and No. 1 c but reading to 3O" can be furnished in place of the 
 regular 5-inch. Made to order only. 
 
 Code Word Bowaiia 
 
 Price, extra $5.O<> 
 
 Beaman Stadia Arc. 
 
 An attachment for reducing inclined stadia readings to horizontal distances, and at 
 the same time, giving differences of elevation between instrument and base of rod. It 
 can be attached to Transits with flat vertical circles 5|, 5 and 4 inches diameter and 
 having the verniers between the legs of standards, as in ]Vo. 1 c. 
 
 It may also be used for arcs with an open edge graduation, as for Plane Table 
 Alidades, etc. Attached to our instruments to order only. See page 197. 
 Code Word Beaman Price, extra $3O.OO 
 
 No. Ic, Style o. 
 
 The Berber Double Opposite Vernier Attachment for transits pro- 
 vided with a 5-incii full vertical circle, verniers reading to minutes. For more in- 
 formation and adjustments of this feature see page 49. Made to order only. 
 
 Code Word Bowek Prijce, extra $2O.O() 
 
 For price of Double Opposite Vernier Attachment with Open Frame protected 
 vertical circle, graduation glass-covered, see page 199. 
 
 Reversion Level. 
 
 Code Word Bowis 
 
 Applicable to any of our Transits of sizes Xo. 1,2 3, 4, 5 and 6. 
 
 Price, extra (over price of transit with level attachment to telescope), 
 
 $12.OO 
 
 NOTE. This. level has a revolvable cover guard to protect the exposed side of the level and to act as a 
 reflector while in use. 
 
 The adjustment of this level and the horizontal cross-wire has to be made in the manner described for 
 the fixed level attached to the transit telescope, see pages 54 and 63. 
 
No. 1 c, Style p. 
 
 in. at edge of jrraduatio 
 
 Tachymeter.* 
 
 For size and particulars, as well as for extras, see pp. 15O-153. 
 
 No. 1 c, Style p. Graduations of horizontal and vertical circles on solid silver, 
 reading to minutes; 6-inch full vertical circle with two double opposite verniers read- 
 ing to minutes ; glass shades over verniers; 3|-inch striding level; gradienter attachment; 
 fixed stadia wires; etc. Standards leather finished. 
 Code Word, Buckwheat. Price as above, $296.OO 
 
 This instrument without a striding level. less, $20.00 
 
 *' " " double opposite verniers for vertical circle, but with a double 
 
 vernier between the legs of the standard as in No. Ic, page 154 . . less, $16.00 
 
 *The name 7^achynteter, or rapid measurer, has been applied for many years, in Europe to instruments of 
 this description. The characteristic of tachymetry is, that all the data required for the location of points are 
 rapidly determined by the instrument, by means of horizontal and vertical angles, and stadia measurements 
 of distance. 
 
157 
 
 No. 1 d. 
 
 As made by C. L. Berger & Sons. 
 
 Tachymeter. 
 
 For size and particulars of this instrument see pages 15O-153. 
 
 !N"o. 1 d, as in cut, graduation of horizontal circle on solid silver, opposite verniers 
 reading to 20"; graduation of vertical arc on solid silver, verniers reading to minutes; 
 glass shades over verniers; detachable reading glasses for both circles, 11^-inch tele- 
 scope showing objects inverted, power 27 diameters; 3^-inch striding level; gradienter 
 attachment; fixed stadia wires; etc. Standards leather finished. 
 Code Word, Bumelia. Price, as above, $312.OO 
 
 No. 1 d, as in cut above, and as described under No. 1 d "Bumelia" but with full 
 vertical circle protected by an aluminum guard as shown in No. 1 c, page 154. 
 
 Code Word, Burton. Price, $321.OO 
 
 This instrument without a detachable reading glass to the vertical arc, less $5.00 
 
 NOTE. For a description of the striding level, its use and adjustment, see page 56. This striding level 
 and the detachable reading glasses, as shown above, can be attached only to our transits of the above descrip- 
 tion; we cannot attach them to instruments already made. 
 
158 
 
 . 1 f. 
 
 is made by C. L. Berger & So 
 
 Tacliymeter. 
 
 With three Leveling Screws and Shifting Center. 
 
 No. 1 f ^ as in cut. Graduation of horizontal circle on solid silver, opposite ver- 
 niers reading to 20'' ; graduation of 5 inch vertical arc on solid silver, verniers reading 
 to minutes; glass shades over verniers ; detachable reading glasses for horizontal 
 circle ; ll|-inch telescope showing objects inverted, power 27 diameters ; 6- inch spirit 
 level parallel to telescope ; 3^ inch striding level ; gradienter attachment ; fixed stadia 
 wires, etc. Standards leather-finished. Price, as above, $322.QO 
 
 For size and particulars of this instrument, as well as for Extras see pages i5-i53- 
 For adjustment of Transverse striding-level resting on special collars see page 5 6 - 
 
 Code word Burdock. 
 
159 
 C. !L. BEBGER & SONS 
 
 No. 1 g. 
 
 in. at edge of graduation.) 
 
 Tacliymeter. 
 
 For size and particulars of tlie above instruments, as well as for extras, see pp. 15O-153. 
 
 NO. 1 g", as in cut. Same as No. 1 f , but having a 5-inch full vertical circle with two 
 double opposite verniers reading to minutes, and two reading-glasses to tJxe vertical 
 circle. 
 
 Code Word, Buttercup. 
 
 Price as above, $352.OO 
 
160 
 
 C. L. BEKGEK & SONS. 
 
 MONITOR TYPE 
 Engineers' Transit No. 1 m. 
 
 With Yoke Standards and Wye-Bearings. Without Compass. 
 For Triangulation, General Construction, Tunnel and all classes of Underground Work. 
 
 In the Transit illustrated on opposite page the yoke-shaped standard frame carrying 
 the wye-bearip^s for the telescope's axis of revolution, is cast in one piece, and its form, 
 being of superior design, is such as to give great upright and lateral stiffness, with compara- 
 tive lightness in weight. This fact, coupled with the desire to have an instrument free 
 from the defects so often noticed in the Transits enumerated under Nos. 1 and 2, 
 etc., with compasses where the necessary lateral rigidity of the standards must be obtained 
 by the peculiar conically-shaped pivot ends of the telescope's axis of revolution, at the 
 expense of accuracy, led us to adopt the cylindrical form of pivots resting in wye 
 bearings, to ensure a true motion of the telescope in the vertical plane, (one that is 
 free from any deflection of the line of sight caused by wabbling in bearings loose from 
 wear and lateral strain). In this Transit the telescope reverses only through the standard, 
 as usual, the aim being to furnish a Transit most eminently fitted for the highest class 
 of engineering work of all kinds, but at a cost lower than those enumerated later on under 
 Triangulation Transits. In this instrument the wye-bearings are well protected from 
 dust and water. The main plate level is placed in the center of the upper plate, where 
 it is entirely protected by the base of the standard frame and by the aid of a special guard, 
 and where it can easily be read from both sides. The upper surface of the vernier plate 
 is slanting downwards, and the vernier openings are raised above the surface, and special 
 channels are provided, so that water will run off immediately. The Yoke standard frame 
 will be leather-finished. In this, as in all other instruments, the fine appearance and 
 general character depends principally on simplicity of design, coupled with tine work- 
 manship, and a high state of efficiency of every part. Other parts that cannot easily 
 be finished and lacquered in the usual but mostly antiquated manner, are therefore 
 also leather-finished. This is in line with good taste and modern thought and im- 
 provements, to enable us to unite as many pieces as possible to secure great stability 
 and steadiness under all conditions in order to arrive at quick and thoroughly reliable 
 results. 
 
 Transit Xo. 1 in, as in cut (for size, weight and particulars, see Transit No. 1, 
 page 142); graduation of horizontal circle on solid silver, double opposite verniers 
 reading to 30"; 'graduation of 5-inch vertical circle on solid silver, double vernier 
 reading to minutes; aluminum guard to vertical circle; glass shades over verniers; 
 Ill-inch erecting telescope with lj-inch aperture; power 24 diameters; long spirit- 
 level to telescope; fixed stadia wires; etc. Made to order only. 
 
 Price, as above $265.OO 
 
 C^de Word Buxana 
 
 This transit can be made with inverting telescope when so ordered; length 12 inches, 
 clear aperture If inches, power 28 diameters. No extra charge. 
 
 If desired with inverting telescope add to the Code word " Invert." 
 
 Oblong Compass permanently fastened to and within the confines of vernier plate 
 
 at side of standard. The 3-inch needle can be read 5 each side of the zero of the 
 
 graduation. 
 
 Cotle Word Oblong. Price extra, $15.OO 
 
1G1 
 C. L. BEKGER & SONS. 
 
 . at edge of graduation.) 
 
 Engineers' Transit No. 1 m. 
 
 With Yoke Standards and Wye-Bearings. Without Compass. 
 For Triangulation. General Construction, Tunnel and all classes of Underground Worn. 
 
162 
 
 64 SURVEYORS' TRANSIT No. 1 s. 
 
 With Compass, Yoke Standards and Wye-Bearings. 
 
 It is well known that in Transits with compass (styles Nos. 1, 2, 3, 4, 5 and 6) the 
 strength required for the standards to support the telescope, and to prevent the latter from 
 shifting laterally in the bearings, is derived mainly from the vernier plate and its compass 
 ring as a base, from the rigidity ot the standards themselves and their width apart, and 
 last but most important from the peculiar shape of the pivot-ends of the horizon- 
 tal axis of revolution, which latter prevents both of the standards from swaying to and 
 fro. Ingenious and time-honored as this construction is being exemplified in many 
 thousands of instruments it cannot compare in degree of accuracy with that afforded 
 when the ends ot the telescope's axis are of cylindrical form running in wye-bearings, pro- 
 vided the necessary upright and lateral stiffness can be obtained in the standard frame. 
 The Yoke standard frame, shown in the cut on opposite page, is of great strength com- 
 bined with lightness, and enables to successfully mount the telescope's axis by means 
 of cylindrical pivots in wye-shaped bearings. The motion of the telescope in the vertical 
 plane is therefore entirely free from such defects, as deflection of the line of sight, etc., 
 noticed in the older styles, when caused by wear and strain. To obviate this, has been 
 the object of introducing the yoke frame common in all our triangulation Transits 
 but having a compass mounted in the central portion of its base. With this arrange- 
 ment the surveyor is now placed in possession of an instrument whose chief features 
 have no superior in point of accuracy, fine workmanship and thorough adaptation to his 
 needs. The telescope reverses through the standards only. The Yoke frame will be 
 leather-finished; all other parts will be polished and lacquered. The whole instrument 
 has a fine appearance. 
 
 Transit No. 1 S, as in cut (for size, weight and particulars, see Transit No. 1 , 
 page 150); graduation of horizontal circle on solid silver, double opposite verniers 
 reading to minutes; 5-inch vertical circle with one double vernier reading to minutes, at 
 eye-end; graduation on solid silver; aluminum guard; glass shades over verniers; llf-inch 
 erect telescope with 1^-inch aperture, power 24- diameters, long spirit-level to telescope; 
 fixed stadia wires; 3 T 9 ^-inch magnetic needle with variation plate; etc. 
 
 Made to order only. 
 
 Price $3OO.OO 
 
 Code Word Buxota. 
 
 Extras to Transit No. 1 s. 
 
 Horizontal circle graduated to read to SO", extra . .10.00 
 
 " " " 20" " . 20.00 
 
 This transit can be made with inverting telescope when so ordered; length 12 inches, 
 clear aperture 1 f inches, power 28 diameters. No extra charge. 
 
 If desired with inverting telescope add to the code word " Invert." 
 
 5s" SURVEYORS' TRANSIT No. 2 s. 
 
 Horizontal circle 5% in. at edge of graduation. 
 
 Tnaiisit No. 2 s (size, weight -and particulars as in No. 2, page 168), but with 
 magnetic needle 2*/" long, variation plate; otherwise with same features as for 
 No. 1 S above. Made to order only 
 
 Price $3OO.OO 
 
 Codeword Buylis. 
 
 This instrument with inverting telescope, add to the Code Word "Invert." 
 
 Transits No. 1 s and No. 2 s, enumerated above, may have a 5" vertical 
 arc, with the verniers between the Yoke standard frame instead 
 of the full vertical circle with the verniers at eye end. 
 
 Price $280.00 
 
 Code Word, Transit No. Is . Buzada. 
 
 " Transit No. 2s Buzemo. 
 
 For prices of solar attachments, etc., see pages 172 to 175. 
 
Patented. 
 
 (6J4 in. at edge of graduation.) 
 
 Surveyors' Transit No. 1 s. 
 
 "With Compass, Yoke Standards and "Wye -Bearings. 
 
 (Above instrument is shown with inverting telescope.) 
 
164 
 
 C. L. BERGER & SONS, BOSTON 
 
 5^" ENGINEERS' AND SURVEYORS' TRANSIT* 
 
 A Standard Size of less weight than transit No. 1, but larger than size No. 2. 
 The^ telescope has nearly the same power as No. 1 Erecting 1 and when made 
 Inverting" is more powerful. 
 
 The outer or contra clockwise row of figures on the horizontal circle and 
 those of the verniers of the right side of verniers A and B can be furnished in Red 
 but will be made to order only, see cat. page 41. Instrument stands upright in 
 carrying case. 
 
 Transit, Size No. 
 
 SPECIFICATIONS : 
 
 Horizontal circle 5 1 /-iiieh (at edge of graduation), graduated on heavy 
 ring of solid silver, double opposite verniers, read to minutes, two rows of 
 figures to 360 in opposite directions; figures inclined in the direction verniers 
 should be read, verniers at 30 to line of sight. 
 
 Vertical circle 5-inch, graduated on solid silver, double verniers read to min- 
 utes, between legs of standard, and Aluminum Guard. 
 
 Telescope lOM-incll, objects erect, f aperture 1 1 4 inch, power 2O dia. 
 
 Stadia wires, fixed, in ratio 1 :100. 
 
 Spirit-level 5!4-inch, with clamp and tangent screw to telescope. 
 
 Plate-levels of standard length and very sensitive. 
 
 Magnetic needle 3!-inch, edge-bar form. (See pages 98-99.) 
 
 Shifting center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 
 Transit leatheri zed (see page 9). All important parts treated in our durable 
 and handsome leather finish. 
 
 Full length split-leg tripod. 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, 
 
 a wrench, a screw-driver, an adjustable plumb-bob, a magnifying glass, an ad- 
 
 justing pin, and weighs about 7 Ibs. 
 
 Weight of transit about 13 Ibs.; weight of tripod from 9 to 9}/ Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 55 Ibs. 
 
 Code Word, Cakula. Made to order only. Price $252.OO 
 
 as above, with a 5-inch Arc in place of a full Vertical Circle. 
 Code Word, Cagana. Made to order only Price, $243.OO 
 
 Transit as under Cagana, but without arc. 
 
 Code Word, Cadagon. Price, $223.OO 
 
 Extras to Transit No. 
 
 Graduation of Horizontal Circle, reading to 30" .... 
 
 Gradienter attachment . . . . 
 
 Offsetting arrangement ........ 
 
 Variation Plate, adapted for all declinations E. or W. .... 
 
 Extension Tripod, in addition to the split-leg tripod furnished with the transit 
 Plain Prism, with colored glass, for observing the sun's altitude (fig. 7), page 175 
 
 $10.00 
 5.00 
 
 10.00 
 19.50 
 8.00 
 
 Improved Prism, with colored glasses, for observing the sun's altitude (fig. 5), page 175 . 12.00 
 Davis' Solar Attachments, screen with improved prism mounting (page 175) 
 Berger's Solar Attachment (small) (pages 172 and 173) . . . 52.00 
 
 " Latitude Level Attachment . . 
 
 Short Focus Lens Attachment (see pages 101 and 203) . . . One $8.50, pair 16.00 
 
 Leather Cover over case arranged to be strapped to a saddle of a horse 
 
 " " " " as above with shoulder straps ...... 15.00 
 
 Cravenette hood (heavy, gives good protection) silk (light, not waterproof), each . 
 
 Bottle of fine watch oil, for the centers, etc., of transit . . - 0.35 
 
 *Unusual size; see our No. 5 1 /? Monitor Transit, pages 166 and 167. 
 
 fAn Inverting Telescope of 1W aperture, lO'/a" long, power 23 dia. can be supplied 
 with the above transit in place of the regular erecting one at no additional cost. This telescope is 
 particularly well adapted for stadia work. Made to order only. 
 
1G5 
 C. L. BEBGER & SONS, BOSTONo 
 
 No. 5 1 / 2 . 
 
 in. at edge of graduation 
 
 Patented. 
 
 No. 5!4 Engineers' and Surveyors' Transit. 
 
 Unusual size, made to order only. (See No. 5% complete Monitor Transit, 
 pages 166 and 167.) 
 
 For size, weight, particulars and extras of this instrument see opposite page. 
 
 Code word Cakula Price, $252.OO 
 
 The Front Plate Level is fully protected its entire length by an aluminum guard 
 which is independent of the level and its adjustments. 
 
 To avoid mistakes and to save time telegraph Code name. 
 
166 
 
 C. L. BERGER & SONS. BOSTON 
 
 5|" MONITOR TYPE 
 Engineers' and Surveyors' Transit 
 
 With Compass. Cylindrical Pivots to Telescope Axis. Wye-Bearings. 
 
 A Standard Size of less weight than transit No. 1 , but larger than sizeNo.2. 
 
 In general use for accurate WOl'k in cities where commercial traffic prevails, in 
 and about factories and erection of buildings. For underground work it has .no supe- 
 rior. The telescope has nearly the same power as No. 1 Erecting 1 and when 
 made Inverting' is more powerful. Modern design, ruggedness of construction, 
 and its great lateral rigidity of standards for steadying the tel- 
 escope's axis place this style on a par with our Yoke Standard Frames, 
 enumerated later on, commending it to all requiring uninterrupted and efficient 
 service in strenuous work. 
 
 The outer or contra clockwise row of figures on the horizontal circle and those of 
 the verniers of the right side of verniers A andB can be furnished in Red but will be 
 made to order only, see cat. page 41. Instrument stands upright in carrying case. 
 
 Monitor Transit, Size No. 
 
 SPECIFICATIONS : 
 
 Horizontal circle 5^ iiicli (at edge of graduation), graduated on heavy 
 ring of solid silver, double* opposite verniers, read to minutes, two rows of 
 figures to 360 in opposite 'directions; figures inclined in the direction 
 verniers should be read, verniers at 30 degrees to line of sight. 
 
 Vertical arc 5-iiich, graduated on solid silver, double verniers read to minutes. 
 
 Telescope lO^-incli, objects erect, i aperture l^-inch, power 2O dia. 
 
 Stadia wires, fixed, in ratio 1 : 100. 
 
 Spirit level 5 >2 -inch, with clamp and tangent screw to telescope. 
 
 Plate levels of standard length and very sensitive. 
 'Magnetic needle 3>-incIi, edge-bar form. (See pages 98-99.) 
 
 Shifting" center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 
 Transit leather ized (see page 9). All important parts treated in our durable 
 and handsome leather finish. 
 
 Full length split-leg- tripod. 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, 
 
 a wrench, a screw-driver, an adjustable plumb-bob, a magnifying glass, an ad- 
 
 justing pin, and weighs about 7 Ibs. 
 
 Weight of transit about 13 Ibs.; weight of tripod from 9 to 9)4 Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 55 Ibs. 
 
 Code word Caboa Price, $243.OO 
 
 Transit as above, but in place of arc with a 5-inch full Vertical Circle 
 
 and Aluminum Guard double verniers between legs of standard. 
 Code word Cafid Price $252.OO 
 
 Extras to Monitor Transit No. 
 
 Graduation of Horizontal Circle, reading to 30" 
 
 Gradienter attachment . ? 
 
 Offsetting arrangement . ... 
 
 Variation Plate, adapted for all declinations E. or W. ,'... ' . ' ' in en 
 
 Extension Tripod, in addition to the split leg tripod furnished with the transit . 
 
 Plain Prism, with colored glass, for observing the sun's altitude (fig. 7), page 175 . 8.00 
 
 Improved Prism, with colored glasses, for observing the sun's altitude (hg. 5), page 175 12 .uu 
 
 Davis' Solar Attachments, screen with improved prism mounting (p. 175) 
 
 Berber's Solar Attachment (small) (pp. 172 and 173) o2.w 
 
 Latitude Level Attachment 
 
 Short Focus Lens Attachment (see pages 101, 203) . One $8.50, pair 
 
 Leather Cover over case arranged to be strapped to a saddle of a horse . . it-yv 
 
 " " "as above with shoulder straps . V'XX 
 
 Cravenette hood (heavy, gives good protection), silk (light, not waterproof), each . i.w 
 
 Bottle of fine watch oil, for the centers, etc., of transit ..... 
 
 "This transit can be furnished with a single B vernier, see Monitor Type transit No. 4 1 A, 
 page]180. Made to order only. 
 
 t An Inverting Telescope of 1/4" aperture, Id/a" long, Ppwer 23 dia. ^n be supplied 
 with the above transit in place of the regular erecting one at no additional cost. J 
 particularly well adapted for stadia work. Made to order only. 
 
167 
 
 C. L. UKlttiKK, & SONS. BOSTON 
 
 Patented. 
 
 No. 5 y? Complete Monitor Type Transit 
 
 For si/.e, weight, particulars and extras of this instrument see opposite page. 
 
 Code word Caboa 
 
 Price, $243.OO 
 
 Cylindrical Pivots to telescope's axis running in the improved. Wye bearing. The 
 center point is located on a round hub on the telescope's axis to better distinguish it in 
 dark places when centering under a point above the transit. 
 
 The Eye Piece Cap is large in diameter. It affords a protection to the eye of the ob- 
 server in a glaring sun. It has been combined with a dust guard which fully protects 
 the Eye Piece focussing slide. 
 
 The Front Plate Level is fully protected its entire length by an aluminum guard 
 which is independent of the level and its adjustments. 
 
 Improved Levelling Head with dust caps to levelling SCI-CAVS. 
 
 To avoid mistakes and to sat'e time telegraph Code name. 
 
168 
 
 5|" ENGINEERS' AND SURVEYORS' TRANSIT. 
 
 The essential features of this transit are like those enumerated under No. 1, 
 page 150, \vith the exception of size and weight. We strongly recommend it for 
 use where a lighter instrument is desirable for land surveying, railroad, mining and 
 underground work, etc., of all kinds and where a graduation reading direct to single 
 minutes and to 30" and 20" by estimation is preferred. Every part is made with great 
 care and the aperture, focal length and power of telescope are properly related to each 
 other and to the size of plate to make this a very compact, portable and accurate transit.* 
 
 Complete Transit Size No. 2. As in cut (see opposite page), but with 
 verniers at 30 to line of sidit (unless ordered to be at 90). 
 
 Horizontal circle 5>^-inch (at edge of graduation), graduated on heavy inlaid 
 ring of solid silver, double opposite verniers reading to minutes, two rows of 
 figures to 360 in opposite directions; figures inclined in the direction verniers 
 should be read; verniers at 30 to line of sight. 
 
 Vertical arc 5-inch, graduated on solid silver, double verniers read to minutes. 
 Telescope lOX-inell, Objects erect, t aperture 1# inch, -power 18 dia. 
 Stadia wires, fixed, in ratio 1:100. 
 
 Spirit level 5>-inch, with clamp and tangent screw to telescope. 
 Plate levels of standard length and very sensitive. 
 Magnetic needle 3%" edge-bar form having no index error. 
 Shifting" center, to set instrument exactly over a given point. 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Standards leather ized (see page 9). 
 Full length split-leg- tripod. 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench, 
 a screw-driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and 
 weighs about 7 Ibs. 
 
 Weight of transit about 10 Ibs. ; weight of tripod from 9 to 9>^ Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 55 Ibs. 
 
 Code Word Calypso. Price, $243.OO 
 
 Transit No. 2 as in Calypso but without solid silver, graduations silvered. 
 
 Code Word Calixa. Price, $228.OO 
 
 Transit No. 2 as in Calypso but -without vertical arc ( see No, 1 a, page 152). 
 
 Code Word Calamus. Price $223.OO 
 
 Transit No. 2 as in Calypso but -without level, clamp, tangent screw, arc 
 or stadia -wires to telescope (see cut Plain Transit No. 1, page 151). 
 
 Code Word Caladium. Price $19O.OO 
 
 Extras to Complete Transit No. 2. 
 
 Standards polished and lacquered (no leather finish). Extra 95. OO 
 
 5-inch full vertical Circle*, in place of arc), graduation on solid silver, double vernier 
 
 between legs of standard reading to minutes, with aluminum guard (as in cut, page 177). . . 9.0O 
 
 Gradienter attachment 5.OO 
 
 Offsetting arrangement 5.0O 
 
 Short FOCUS Lens (see pp. 101, 203). One pair 16.OO 
 
 Variation Plate, to set off all declinations E. or \V 1O.OO 
 
 Cravenette hood (heavy, gives good protection); Silk (light, not waterproof), each . . 1.00 
 
 Bottle Of fine watch-oil, to lubricate the center, etc., of transit O.35 
 
 *For close stadia work, Transit telescope size No. 1, with its longer focal length and higher power, will 
 be best suited for that purpose. But in all cases where greater lightness and portability and where only general 
 good results in stadia work, as obtained with a less powerful telescope, will be deemed satisfactory, size No. J8 
 should be chosen. We cannot put a telescope of the size described under No. i upon a Transit size No. 2. 
 
 t An Inverting Telescope of 1%" aperture, 1O% inches long and with a power of 22 dia. can 
 be supplied with the above transits in place of the regular erecting one at no additional cost, but the in- 
 strument must be made to order. This telescope is particularly well adapted for stadia work. 
 
169 
 C. L. BERGEK & SONS. 
 
 No. 2. 
 
 n. at edge of graduation) 
 
 5-inch Complete Engineers' and Surveyors' Transit. 
 
 For size, weight, particulars and extras of this instrument see opposite page. 
 
 Transit Xo. 2, as already described on opppsite page Calypso and as shown 
 above, but with verniers at 3O to line of sight (unless ordered to be at 90), grad- 
 uations on solid silver, fixed stadia wires. 
 
 Code word, Calypso. Price $243.OO 
 
 (For code words for Extras and chauges from Calypso, 
 see pages C, E and F of complete code at back.) 
 
 NOTE If verniers are desired at 90 to line of sight, as in cut above, the instrument 
 must be made specially, no extra charge. 
 
The Surveyors' Solar Attachment. 
 
 Placed on the side of the transit it permits the main telescope to be reversed through 
 
 the standards at all times. 
 
 Our Surveyor's Solar Attachment, or meridian finder, is in principle like Pear- 
 son's (made by us heretofore), not requiring computation, but instead of the lens-bar 
 it has a small telescope with -inch aperture and 6 inches focal length. This telescope 
 is provided with a detachable prism and colored glass for the eye-piece, and also a plain 
 colored glass for use with the main, or solar telescope, and our customary solar square 
 as in figure RK, page 122. 
 
 This solar attaches by means of a screw to the end of the cross-axis of the transit 
 telescope on the side of the clamp and tangent-screw, as shown in the cut, and when 
 not in use can be again readily detached from the instrument proper. It has no dec- 
 lination arc. The declination of the sun, and the latitude of the place of observation 
 are both set by the vertical circle of the transit. All settings for position, viz., that 
 of the polar axis for latitude, that is, for coincidence with the zero marks of the vertical 
 circle and verniers, and the setting of the declination, are secured by two spirit levels 
 placed upon the polar axis and upon the solar telescope, as will be seen in the cut. 
 The degree of precision attainable and the ease of manipulation in the use of this 
 attachment is commensurate with that of our engineers' and surveyors' transit. 
 
 To determine true meridian at any hour of a day, it is only necessary that the 
 declination and refraction of the sun on that particular day and hour be known to the 
 observer, and that the polar axis be raised precisely to the co-latitude of the place of 
 observation. 
 
 By the use of our Latitude Level (also attaching to the cross-axis at the side 
 of the vertical circle, as shown in the second cut), not requiring a reading of the ver- 
 tical circle for eveiy setting of the polar axis for latitude except once in a day, obser- 
 vations can be made repeatedly with speed and accuracy. With the declination and 
 refraction of the sun previously worked out for the various hours of a day, observa- 
 tions can be made nearly as fast as a needle can be read of the surveyor's compass. 
 
 A concise description of both attachments will be found in our manual. The ac- 
 companying illustrations of the solar attachment represent them as applied to transits 
 No. 1 and No. 2. Of all the different kinds in use, we believe it to be the most 
 efficient. Owing to its position at the side of the transit, it can be easily 
 manipulated. The adjustments are few and simple, and need to be verified only 
 from time to time ; besides, they can be readily proved and perfected, being similar to 
 those in the transit. 
 
 Weight of this Solar attachment is 1 lb., that of the latitude level about Ib. 
 Both are packed in a separate box of mahogany provided with a shoulder strap, 
 
 and can also be packed in the box with the instrument. 
 
 Price of Solar attachment, as above, with counterpoise, prism with colored 
 glasses and additional colored glass to apply to the telescope of the transit to 
 observe the sun's altitude, in order to apply the correction for refraction in 
 solar transit work, . ...,,.... $85.OO 
 
 Price of latitude level, as above, .,.... 15.OO 
 
 Surveyors' Solar Attachment (Smith Solar), as used by " General 
 Land Office of U. S. A.," attached to transits No. 1-s and No. 2-s on pages 
 
 162 and 163 as well as the 4^" transit of the same style. 
 
 Complete Transits No. 1-s, No. 2-s and No. 4!-s with Smith 
 Solar, Price, $363.OO 
 
171 
 
 C. L. BERGER & SONS. 
 
 Surveyors' Solar Attachment. 
 
 Latitude Level Attachment. 
 
 Shown as applied to a Transit with Solar Attachment. 
 
 NoTE.-The surveyors' solar attachment and our latitude level can be placed only upon Transits No. 
 No. 2, and No. 3, and then only when ordered with the instrument. 
 
172 
 
 The Berger Solar Attachment 
 
 Attachable to Transits, Sizes 1, 5'/2, 2, 4 '/a and 4, having a Full Vertical Circle. 
 For U. S. Deputy Surveyors, Surveyors and Mining Engineers. 
 
 This Solar Attachment may be used as a first-class solar in surface surveying for 
 determining meridian. The solar telescope being longer and more powerful than 
 heretofore, and as its horizontal axis is provided with our patented lateral adjust- 
 ment * (see cuts a, a on right-hand side of illustration), we are enabled to place its 
 line of collimation so truly above that of the main telescope as to be exactly in the 
 same vertical plane. 
 
 As a solar attachment, or meridian finder, it is in principle like Pearsons' and that 
 formerly made by us (see cut page 65), not requiring computation; but instead of the 
 lens bar, or small telescope, f it is now constructed with a telescope of one-inch aperture 
 and six-inch focal length, provided with a diagonal eye-piece, colored glass and wires 
 arranged in a square, as shown on next page and described on page 71. 
 
 This solar attachment fastens by means of a screw to the cross axis of the transit 
 telescope. It has no declination arc. The declination of the sun and the co-latitude 
 of the place of observation are both set off by the vertical circle of the transit. All 
 settings for position, viz. that of the polar axis, to be truly at right angles to line of 
 sight of main telescope and the setting of the declination, are secured by the spirit 
 level attached to the solar telescope. The degree of precision and simplicity of manipu- 
 lation attained thereby is commensurate with that of our Engineers' Transit. 
 
 To determine true meridian at any hour of the day it is only necessary that the 
 declination and refraction of the sun on that particular day and hour be known to the 
 observer, and that the polar axis be raised precisely to the co-latitude of the place of 
 observation. The adjustments are few and simple, and need to be verified only from 
 time to time; besides, they can be readily verified, being similar to those in the transit 
 proper. 
 
 Latitude and transit observations can also be made with this telescope when the 
 sun's altitude is too high for observations with the mam telescope, in the same man- 
 ner as described on page 97 for our Interchangeable Auxiliary Telescope style 1. 
 
 This solar attachment can be readily attached or detached from the transit with- 
 out altering its adjustments. When detached the transit is then simply an ordinary 
 complete Engineers' and Surveyors' Transit. 
 
 By the use of our Latitude Level t (fastening to the cross axis at the side of the 
 vertical circle, see cut) not requiring a reading of the vertical circle for every setting 
 of the polar axis for latitude except once in a day, observations can be made repeatedly 
 with speed and accuracy. Indeed, with the declination and refraction of the sun pre- 
 viously worked out for the various hours of the day, observations can be made nearly 
 as fast as a needle of the surveyor's compass can be read. A concise description and 
 use of both attachments will be found in the Manual. 
 
 The weight of the solar attachment and top telescope combined is 1 lb., with coun- 
 terpoise, 2 Ibs. ; that of the latitude level about }4 lb. Both are screwed into the in- 
 :ode Words s trument box. 
 
 Manthus Price of Solar Attachment with Small Telescope, as 
 
 generally supplied for solar work, without counterpoise,! but 
 
 with prism and colored glass, $52.OO 
 
 Hcentra Price of Latitude Level, as in cut, $15.OO 
 
 * Other telescopic solars of similar design as heretofore made may be out from y% to }" from the 
 center of the main telescope, and then of course there must be a divergence of the lines of sight of 
 both telescopes involving errors to that amount. 
 
 fThe honor of first conceiving the idea of applying a small telescope in place of the lens bar and 
 of using a spirit level for the accurate setting of the polar axis, belongs to Mr. C. L. Berger, of this 
 firm. See Catalogue of 1878. 
 
 JThis latitude level can also be used for grades and distance measurements, etc. It will be found 
 to form a very useful adjunct to the Engineers' Transit, even without the solar attachment. 
 
 It is not strictly necessary to counterpoise the smaller solar attachment in order to obtain good 
 work. 
 
173 
 
 a 
 
 The Berber 
 Solar Attachment. 
 
 A. Instrument with Solar Attachment ready for an observation. 
 
 B. Eye end view of Solar Attachment showing: patent lateral adjustment to enable us to place 
 the Solar Telescope exactly In the same vertical plane with the main one. 
 
 D. Latitude Level, If ordered, for use with Solar Attachment, 
 b, b. Wire Diaphragrm in Solar Telescope. 
 
174 
 
 Davis' Patent Solar Attachment. 
 
 This invention is destined to supersede all other solar attachments, being by far 
 the most accurate, the most aimpU, and the cheapest in use. The sun observations are 
 made with the instrument's telescope direct, whereby greater range and power are 
 secured, and limiting the adjustments to those common to the instrument proper 
 itself. It can be attached to any engineers' and surveyors' transit which has a good 
 vertical arc or full vertical circle. A great many have been placed on our transits 
 (sizes Nos. 1, 2, 3 and occasionally on No. 4), for the use of U. S. Deputy Survey- 
 ors, and others having occasion to do solar work. 
 
 However, as its manipulation involves a few mathematical calculations, differing 
 somewhat from ordinary solar attachments, we advise our patrons to carefully read 
 pages 81 and 82, etc., of manual, where a full description will be found. 
 
 The screen, shown in Fig. 2, can be applied with erecting and inverting tele- 
 scopes. In making an observation with an erecting telescope the full aperture of 
 the object glass is utilized, but with an inverting telescope it must be limited 
 to about X or ^ inch diameter to get the wires sharply defined on the screen. To 
 this end the telescope cap is provided with a central opening, permitting of such an 
 adjustment, which may be closed entirely when not in use. 
 
 Attachments shown in Figs. 3 and 4 are for direct observation when the sun's 
 altitude does not require the screen. These latter attachments are now made by us 
 in a manner superior to those shown in these cuts on opposite page. They are 
 mounted as in Fig. 5, upon a frame, readily attachable to the eye-piece by means of 
 a clamp, which can be clamped in any position most convenient for the observer. 
 To bring the colored glasses or the prism before the peep-hole of the eye-piece, it is 
 only necessary to revolve them, hence they can be used in rapid succession. It will 
 be seen that these solar attachments are easy to manipulate, and therefore must 
 insure better results than heretofore obtainable with mechanical devices of any 
 other kind. 
 
 Price of Solar Screen, Figs. 1, 2 and 3 -16.00 
 
 " " Plain colored glass, Fig'. 4 2.00 
 
 " " " " " mounted in Shutter, Fig. C>, when ordered 
 
 with Transit 2.50 
 
 " Fig. 6 with Eye Piece Cap, when subse- 
 quently ordered . . ... 3.00 
 
 " " Prism and colored glass, Fig. 7 8.00 
 
 ' " Prism and colored glass, improved mounting, Fig. 5 . . 12.00 
 
 u " Solar Screen with improved prism and colored glasses combined. 18.00 
 
 Code-Daphne 
 
 C. L. Berger & Sons' Patent Inclined Square. 
 
 For Sun Observations with Davis' Patent Solar Attachment. 
 
 This device consists of four additional wires forming an inclined square of equal sides placed at an angle of 
 45 with the usual cross wires, and equi-distant from the latter's point of intersection in the Surveyor's Transit 
 Telescope. The space contained within this square, as will be seen in the greatly enlarged Figures g and a, is 
 slightly smaller than the sun's disc ; thus an observation of the sun for position can be made by simply setting 
 the telescope by means of the tangent screws until the four segments, formed by the black lines against the bright 
 disc of the sun, are of equal size. In this manner the sun's disc can be better bisected, as when it must be 
 quartered by the cross lines alone but, if desired, both methods can be applied as a check upon each other. 
 
 The arrangement of the wires in the inclined square is in no way confusing, as it keeps the cross and stadia 
 wires distinctly apart for the regular work of the transit, and, in rapid work, is a help to distinguish the 
 horizontal from the stadia wires, as shown above, which cannot be said of the erect square H also patented, 
 shown on the page illustrating the various sighting wire diaphragms. Part T. 
 
 Price of Patent Inclined Square, but only, when ordered with the instrument, extra . 84.no 
 
 also provided with Stadia Wires, as in cut, . 7.0O 
 
 ** " " with cross and stadia wires for instruments of other make 10.09 
 
175 
 
 C. 1. BERGEK & SONS. 
 
 Fig. 2. 
 
 Fig.l 
 
 Fig. 3. 
 
 Solar Screen 
 Daisy 
 
 Davis* Solar Attachments, 
 
 Fig. 4. 
 
 Glass 
 
 mounted in 
 Cap. 
 
 Dandelion 
 
 Attachable to any of our 
 Transit Eyepiece Caps 
 
 Fig. 6. 
 
 Glass 
 
 mounted in 
 Shutter. 
 
 Daorma. 
 
 Fig. 5. 
 Dahlia. 
 
 Plain Prism 
 with colored glass 
 
 Attached to Eyepiece Cap. 
 
 Ber 
 
 ger Improved Prism and colored glass attachment 
 
 " A " Prism, " B " Peephole, " C " Colored Glasses. 
 
 NOTE. 
 
 A diagonal Eyepiece cannot be 
 advantageously attached to a 
 mine transit, since it must inter- 
 change with the regular eyepiece 
 of the inverting kind, and there- 
 fore frequent breaking of the cross 
 wires from dirt and water would 
 be a constant source of annoy- 
 ance, especially in dark places. Beside 
 such instruments the telescope must I 
 pushed considerably farther through 
 axis and a heavy counterpoise permanently 
 attached to the eye-end of barrel to balance 
 the telescope, and the latter will then only reverse at eye- 
 end through the standards. For sights inaccessible to the 
 main telescope in mine work, nothing better has been 
 introduced than our interchangeable auxiliary telescope, 
 described later on. 
 
 Fig. 8. 
 
 Diagonal Eyepiece with Swivel Adapter 
 
 for Zenith Stellar Observations 
 
 applicable only to 
 Inverting telescopes of 
 
 Transit-Theodolites 
 
 Zenith 
 
 Price, $20.00 
 
176 
 
 THE 5|" MOUNTAIN TRANSIT. 
 
 This instrument is of the same size and in other respects similar to that described 
 under Transit size No. 2, but being intended for use in mountainous regions, it is pro- 
 vided with an extension tripod to adapt it to suddenly changing grades, and in order 
 to facilitate the reading of the verniers without stepping aside the latter are placed at 
 an angle of 30 to line of sight. This transit has a full vertical circle protected by 
 an aluminum guard. Its work is as accurate as that of larger transits of its class. 
 
 Mountain Transit No. 2. A's in cut shown on opposite page, but without 
 Davis Solar Screen. SPECIFICATIONS :- 
 
 Horizontal circle 5H n ch (at edge of graduation), graduated on heavy inlaid 
 ring of solid silver, double opposite verniers read to minutes, two rows of 
 figures to 360 in opposite directions; figures inclined in the direction verniers 
 should be read; verniers at 30 to line of sight. 
 
 Vertical circle 5-inch, graduated on solid silver, double verniers read to minutes. 
 Telescope 1 OX -inch, objects erect,* aperture 1*4 inch, power 18 dia. 
 Stadia wires, fixed, in ratio 1:100. 
 
 Spirit level 5^ -inch, with clamp and tangent screw to telescope. 
 Plate levels of standard length and very sensitive. 
 Magnetic needle 3%" edge-bar form having no index error. 
 Shifting" center, to set instrument exactly over a given point. 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Standards leatherized (see page 9). 
 Extension tripod. 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench, 
 a screw-driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and 
 weighs about 7 Ibs. 
 
 Weight of transit about 10 Ibs. ; weight of extension tripod from 9 to 11 ^ Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 55 Ibs. 
 
 Code word Forsythia. Price, $252.OO 
 
 A reduction of $15.OO can be made if graduations are not on solid silver. 
 
 Extras to Mountain Transit No. 2. 
 
 Gradienter Attachment, ..... .... $5.00 
 
 Offsetting arrangement, .......... 5.00 
 
 Variation Plate, adapted for all declinations E. or W 10.00 
 
 Quick leveling attachment (see manual), ...... 15.00 
 
 Full length split-leg tripod, for use with transit in ordinary practice (see Note) 16.50 
 
 Plain Prism, t with colored glass, for observing the sun's altitude (fig. 1), 8.00 
 
 Improved Prism, with colored glasses, for observing the sun's altitude (fig. 5), 12.00 
 
 Davis' Solar Attachments, screen with improved prism mounting (p. 175), 18.00 
 
 Berger's Solar attachment (pp. 172 and 173), . 70.00 
 
 " Latitude Level attachment, ....... 15 00 
 
 Short Focus Lens Attachment (see pages 101, 203). One pair, . . . 16.00 
 
 Leather Cover over case arranged to be strapped to the saddle of a horse, 13.00 
 
 " " " " as above with shoulder straps, .... 15.00 
 
 Cravenettehood (heavy, gives good protection); silk (light, not waterproof ), each 1.00 
 
 Bottle of fine watch oil, for the centers of transit, . . . . . 0.35 
 
 NOTE. Although the extension tripod is very slender and about 2 Ibs. heavier than our regular tripod, its 
 superiority for mountain work is very apparent. Still, for general practice, it is desirable to have the regular 
 tripod, giving greater steadiness and increased accuracy. It will be advantageous to order both kinds. 
 
 It will be observed that in the cut the verniers of the horizontal circle are placed at an angle of 35 to the line 
 of sight as in our Mining Transits, thus adapting the instrument to the work in a mountainous country. On 
 the other hand this change in the position of the verniers requires the level in front of the telescope to be 
 carried beyond the limit of the plate in order to be of standard length and character, and although fully pro- 
 tected in its partially exposed position from injury, by an improved guard surrounding it, it is, nevertheless, 
 subject to slight changes in adjustment, as when compared with one mounted as shown in Transit No. 2, where 
 verniers are placed at 90 to the telescope. In all cases where this change in the position of the verniers is not 
 deemed of sufficient importance, we advise to order our Transit No 2. A small striding level, illustrated in 
 Transit No. Id, can also be placed upon the telescope axis at an extra cost of $15.00. 
 
 * An Inverting Telescope of 1%" aperture, 1O% inches long and with a power of 23 dia. 
 
 can be supplied with the above transit in place of the regular erecting one ; t n > additional cost, but the 
 instrument must be made to order. This telescope is particularly well adapted for stadia work. 
 
 t In a mountainous country, it frequently happens that a transit must be set up in places where it is ex- 
 tremely difficult to gjet standing room to take both back and fore-sights. With the aid of a prism, attached to 
 the eye-piece, all this can be done from the side of the instrument. 
 
C. L. BEKGEK & SONS. 
 
 in. at edge of graduation 
 
 Patented. 
 
 Mountain Transit No. 2. 
 
 (Shown with Solar Screen Attachment.*) 
 
 For size, weight, particulars and extras of this instrument see opposite page. 
 Code Word (without screen), Forsythia. Price $252.OO 
 
 (For code words for Extras and changes from Forsythia, 
 see pages C, F and Gr of complete code at back.) 
 
 * For description of this Solar Attachment see page 81 of the Manual, and for illus- 
 tration and prices see pages 174 and 175. 
 
178 
 
 The 41" Mountain and Mining: Transit. 
 
 . For those desiring a Transit smaller than the 5^" Mountain Transit just described 
 and illustrated under No. 2, but larger than our Transit No. 4 (pages 18*' 183) we fur- 
 nish this one in size and weight between the two. With this exception the instru- 
 ment is like our Transit No. 4, as will be seen by comparing the cuts. It has com- 
 pound centers. With careful use, necessary only on acount -of its lightness,* it is 
 capable of very accurate results. Owing to the short focal length and high power of 
 the telescope we strongly recommend the inverting kind, although an erecting one 
 can be supplied to order. Instrument packed to stand upright in carrying case. 
 
 Transit No. 4^ 
 
 SPECIFICATIONS : 
 
 Horizontal circle 4^-inch, graduated on heavy inlaid ring of solid silver, double opposite 
 verniers reading to minutes, two rows of figures to 360 in opposite directions, figures in- 
 clined in the direction verniers should be read, verniers at 35 to line of sight 
 Vertical circle 4-inch graduated on solid silver, double verniers reading to minutes 
 Telescope 7^-inch, objects inverting, aperture IVe inch, power 18 dia. 
 Stadia wires, fixed, in ratio 1: 100. 
 
 Spirit level 4-inch, with clamp and tangent screw to telescope. 
 Plate levels both of standard length and very sensitive. 
 Magnetic needle 3-inch edge-bar form having no index error. 
 Shifting center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Standards leather finish. 
 Extension tripod.* 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench, a screw- 
 driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and weighs about 4 Ibs. 
 
 Weight of transit about G*/ 2 Ibs. ; weight of extension tripod about 9 Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 50 Ibs. 
 
 code word Genila. Price, $247.OO 
 
 Extras to Transit No. 4V2. 
 
 $ 5.OO 
 10.00 
 8.0O 
 4.OO 
 8.5O 
 
 198 . . 35.00 
 
 98 45.OO 
 
 Gradienter attachment 
 
 Variation plate to set off all declinations E. or W 
 
 Prism and colored glass (plain form only permissible, Fig 3, page 175) 
 
 Reflector for illuminating the cross wires 
 
 Short focus lens, pages 101, 203, one 
 
 Edge graduation for vertical circle, with a double vernier at eye end, page 
 Edge graduation for vertical circle, with double opposite verniers, page 19i 
 Patent interchangeable auxiliary telescope, style I, page 189 . . 37.0O 
 
 Berger solar attachment with small telescope, page 172 5/8.OO 
 
 Split-leg tripod in addition to extension tripod furnished with the transit .... 16.5O 
 
 Bracket in box, page 203 14.OO 
 
 Trivets, page 204 
 
 Lateral adjuster, page 205 25.OO 
 
 Leather cover with shoulder straps 1 3.0O 
 
 " without " " 11.00 
 
 Hood to protect transit from rain and dust l.OO 
 
 Bottle of fine watch oil .35 
 
 * We furnish with this instrument a heavy extension tripod, such as furnished with transit size No. 2 
 This secures to the transit the necessary great rigidity and stability. However, when required, we 
 can furnish an extension tripod weighing 7 Ibs. only (price being the same), in place of the 9^4 lb. 
 tripod, or in addition if desired for special purposes. We can also furnish the stiffer split-leg tripod 
 weighing only 7J- Ibs. in place of the extension tripod. This we recommend very strongly whenever 
 applicable. 
 
179 
 
 C. I,. BEKGEK & SONS. 
 
 No. 
 
 n. at edge of graduation). 
 
 Complete 
 Mountain and Mining Transit. 
 
 For size and particulars of this instrument, as well as for Kxtras, see opposite page. 
 
 Code word, Genila. Price, $247.OO 
 
180 
 C. L,. BERGER & SONS. BOSTON 
 
 4|" MONITOR TYPE Transit. 
 
 With Compass. Cylindrical Pivots to telescope axis. Wye- Bearings. 
 
 This Monitor Type transit has been designed to meet a demand for a 
 lighter instrument than size No. 5>^ Monitor Transit. 
 
 The same general description of our No. 5H Monitor Transit, page 166, ap- 
 plies to this No. 4:}^ Type with the exception that vernier B is single, which en- 
 
 ables US to place an unusually long, sensitive and fully protected front plate level 011 
 this small transit and does not project over the vernier plate. We do not furnish a 
 double B vernier. On just this one feature alone this type With the double A 
 
 vernier and the single B vernier is destined to supersede the regular types 
 made, as it lessens the tendency toward errors. In general practice a reading: on a 
 
 Berg'er transit is at once accurate and sufficient. However, if the A and B double 
 
 verniers are wanted we advise ordering No. 4^ transit on page 179. 
 
 The outer or contra clockwise row of figures on the horizontal circle and the 
 corresponding figures of the right side of vernier A can be furnished in Red but will 
 be made to order only, see cat. page 41. Instrument stands upright in carrying case. 
 
 Monitor Transit No. 4, 
 
 SPECIFICATIONS : 
 
 Horizontal circle 4%-inch, graduated on heavy ring of solid silver. A vernier is double. 
 B vernier Is single reading to minutes, two rows of figures to 360 in opposite directions. 
 Figures inclined in the directions verniers should be read : Verniers at 35 to line of sight. 
 Vertical Arc 4-inch, graduated on solid silver, double verniers, reading to minutes. 
 Telescope 8-inch, objects erect,* aperture l l /& inch, power 19 diameter. 
 Stadia wires, fixed, in ratio 1 : 10O. 
 
 Spirit level 4-inch with clamp and tangent screw to telescope. 
 Plate levels both of standard length and very sensitive. 
 Magnetic needle 2fi inch edge-bar form having no index error. 
 Shifting center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Transit leather finished. 
 Extension tripod. t 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench, a screw- 
 driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and weighs about 4 Ibs. 
 
 Weight of transit about Q% Ibs. ; \veight of extension tripod about 9 Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 50 Ibs. 
 
 Code word Geminol. 
 
 Price $1 
 
 Monitor Transit No. 4V as above, but with 4" full Vertical 
 circle and aluminum guard in place of arc. 
 
 Codeword Genony. 
 
 Price 
 
 Extras to Transit No. 
 
 Gradienter attachment 
 
 Variation plate to set off all declinations E. or W. 
 
 Prism and colored glass (plain form only permissible, Fig. 7, page 175) 
 
 Reflector for illuminating the cross wires 
 
 Short focug lens, pages 101, 203, one 
 
 Edge graduation for vertical circle, with a double vernier at eye end, page 198 
 
 Edge graduation for vertical circle, with double opposite verniers, page 198 
 
 Patent interchangeable auxiliary teles'cope, style I, page 189 
 
 Berger solar attachment with small telescope, page 172 
 
 Split-leg tripod in addition to extension tripod furnished with the transit . 
 
 Bracket in box, page 203 
 
 Trivets, page 204 .... 
 
 Lateral adjuster, page 205 . 
 
 Leather cover with shoulder straps 
 
 without " 
 
 Hood to protect transit from rain and dust 
 , Bottle of fine watch oil . 
 
 * 5.00 
 
 10.00 
 
 8.00 
 
 4.00 
 
 8.50 
 
 35.00 
 
 45.00 
 
 37.0O 
 
 58.00 
 
 16.50 
 
 14.00 
 
 25.00 
 
 13.00 
 
 11.00 
 
 1.00 
 
 .35 
 
 *An Inverting Telescope of l'/ 8 " aperture, TtVa" long, power 18 dia. can be supplied with 
 the above transit in place of the regular erecting one at no additional cost. This telescope is partic- 
 ularly well adapted for stadia work. Made to order only. 
 
 t We furnish with this instrument a heavy extension tripod, such as furnished with transit size No. 2. 
 This secures to the transit the necessary great rigidity and stability. However, when required, we 
 can furnish an extension tripod weighing 7 Ibs. only (price being the same), in place of the 9M lb. 
 tripod, or in addition if desired for special purposes. We can also furnish the stiffer split-leg tripod 
 weighing only 7^4 Ibs. in place of the extension tripod. This we recommend very strongly whenever 
 applicable. 
 
181 
 
 C. L. BEKGER & SONS. BOSTON 
 
 NO. 
 
 iii. at edge of graduation) 
 
 No. 4^ Complete Monitor Type Transit 
 
 F>r size and particulars of this instrument, as wi'H as for Extras, see page 18O. 
 
 Code word, Geniinol 
 
 Price, 
 
 $248.00 
 
 Cylindrical Pivots to telescope's axis running in tlie improved adjustable Wye- 
 Block Bearing. The center point is located on a round hub on the telescope's axis to 
 letter distinguish it in dark places when centering under a point above the transit. 
 
 The Eye-Piece Cap is large in diameter. It affords a protection to the eye of the ob- 
 server in a glaring sun. It has been combined with a dust guard which fully protects 
 the Eye-Piece focussing slide. 
 
 The Front Plate Level is fully protected. Improved Leveling Head with dust caps 
 to leveling screws. 
 
 To avoid mistakes and to save time telegraph Code name. 
 
182 
 
 The 4" Mountain, 
 
 Mining and Reconnoissance Transit. 
 
 The smallest Transit made by us. 
 
 The CUt represents a complete transit of this class, in every respect similar to our En- 
 gineers' and Surveyors' large transits No. 1 and No. 2, except in size and weight. The 
 
 verniers of the horizontal circle are placed at 35 to line of sight, unless ordered to be 
 at 90, when the transit must be specially made. The instrument has compound centers 
 and is as carefully made as the larger ones, and with careful use, necessary only on ac- 
 count of its great lightness,* capable of very accurate results. For use in mines, moun- 
 tains and for explorers, travelers and for preliminary work of all kinds, as well as to 
 fill in details, it is especially adapted. Owing to the small size of telescope and high 
 power, we supply the inverting kind. The instrument is packed lying down. 
 
 Transit No. 4 SPECIPICATI ON S: - 
 
 Horizontal circle 4-inch, graduated on heavy inlaid ring of solid silver, double opposite 
 verniers reading to minutes, two rows of figures to 360 in opposite directions, figures in- 
 clined in the direction verniers should be read, verniers at 35 to line of sight. 
 Vertical circle 4-inch graduated on solid silver, double verniers reading to minutes. 
 Telescope 7%-inch, objects inverting, aperture I'/s inch, power 18 dia. 
 Stadia wires, fixed, in ratio 1:10U 
 
 Spirit level 4-inch, with clamp and tangent screw to telescope. 
 Plate levels both of standard length and very sensitive. 
 Magnetic needle 2%-inch edge-bar form having no index error. 
 Shifting center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Standards metal finish. 
 Extension tripod.* 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench, a screw- 
 driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and weighs about 4 Ibs. 
 
 "Weight of transit about 5 Ibs. ; weight of extension tripod about 9 Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 45 Ibs. 
 
 Code word Genista. Price, $247.OO 
 
 Mountain, Mining and R. Transit No. 4, as above, but 
 with arc only in place of full vertical circle and guard. 
 Code word, Galanthus. Price, $238.OO 
 
 Extras to Transit No. 4. 
 
 Gradienter attachment $ 5.OO 
 
 Variation plate to set off all declinations E. or W 1O.OO 
 
 Prism and colored glass (plain form only permissible, Fig. 7, page 175) 8.OO 
 
 Reflector for illuminating the cross wires 4.OO 
 
 Short focus lens, pages 101, 203, one 8.5O 
 
 Edge graduation for vertical circle, with a double vernier at eye end, page 198 . . 35.OO 
 
 Edge graduation for vertical circle, with double opposite verniers, page 198 . . . 45. OO 
 
 Patent interchangeable auxiliary telescope, style I, page 189 . . STf.OO 
 
 Berger solar attachment with small telescope, page 172 52.OO 
 
 Split-leg tripod in addition to extension tripod furnished with the transit .... 16.5O 
 
 Bracket in box, page 203 14.OO 
 
 Trivets, page 204 
 
 Lateral adjuster, page 205 25.OO 
 
 Leather cover with shoulder straps 12.5O 
 
 " without " " 10-50 
 
 Hood to protect transit from rain and dust l.OO 
 
 Bottle of fine watch oil . -35 
 
 * We furnish with this instrument a heavy extension tripod, such as furnished with transit size No. 2. 
 This secures to the transit the necessary great rigidity and stability. However, when required, we 
 can furnish an extension tripod weighing 7 Ibs. only (price being the same), in place of the 9M Ib. 
 tripod, or in addition if desired for special purposes. We can also furnish the stiffer split-leg tripod 
 weighing only 73^ Ibs. in place of the extension tripod. This we recommend very strongly whenever 
 ipplicable. 
 
 appl 
 
183 
 C. L. BERGER & SONS. 
 
 No. 4 
 
 (4 in. at edge of graduation.) 
 
 Instrument 
 Packed Ikying Down 
 
 Complete 
 
 Mountain, Mining and Reconnoissance. Transit. 
 
 For size and particulars of this instrument, as well as for Extras, see opposite page. 
 
 Code word, Genista. Price, as above, $247.OO 
 
 (For code words for Extras and changes from Genista, 
 see pages C, F and G- of complete code at back.) 
 
184 
 
 The 4" 
 Complete Transit- Theodolite No. 4b. 
 
 With Yoke Standards and Wye-Bearings. Without Compass. 
 Size as in No. 4, page 182. 
 
 For triangulatioii, filling- in details, etc., in secondary triangular 
 tioii, also for explorers, engineers and surveyors where the large instruments 
 described under No. 11, etc., become undesirable on account of their size and weight. 
 
 The Yoke Standard frame is of our advanced pattern, cast in a single piece 
 of aluminum * (unless ordered to be of brass composition), to gain great lateral stiff- 
 ness, and is leatherized. The inverting telescope can be reversed over the bearings by 
 turning the upper covers aside, and also in the usual way through the standards. The 
 graduation of the horizontal circle and its verniers are protected by glass. 
 
 If double opposite verniers are desired for the vertical circle the figures will then 
 run from 0-90-0 and back (as in the regular field instruments), instead of clockwise with 
 single opposite verniers enumerated below. A level is attached to the vernier arm 
 (instead of to the telescope as in Xo. 4). This instrument will be made with three lev- 
 eling screws only and packed lying down in its carrying case. 
 
 Made to order only. 
 
 Complete Transit-Theodolite No. 4 b, as in cut on opposite page. 
 
 SPECIFICATIONS: 
 
 Horizontal circle 4-iiicli (at edge of graduation), graduated on heavy inlaid 
 ring of solid silver, single opposite verniers read to minutes, one row of figures 
 to 360; verniers at 90 to line of sight. 
 Vertical circle 4-iiich, graduated on solid silver, single opposite verniers read 
 
 to minutes, one row of figures 0-360 clockwise (unless ordered otherwise). 
 Compound centers of bell metal. 
 
 Telescope 7^-illch, Objects inverting, aperture l 1 ^ inch, power 18dia. 
 Stadia wires, fixed, in ratio 1 : 100 
 
 Spirit level 2^-indl, with reversible clamp and tangent screw to vernier arm 
 Striding" level rests at points of contact in wyes. 
 Reading glasses to horizontal and vertical circles. 
 Plate levels both of standard length and very sensitive. 
 Shifting center, to set instrument exactly over a given point. 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Standards leatherized (see page 9). 
 Extension tripod. 
 
 The Mahogany case has a leather strap, hooks, etc. It contains a sun-shade, a wrench 
 a screw-driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and 
 weighs about 7 Ibs. 
 
 Weight of transit about 5 Ibs; weight of extension tripod 9 Ibs. 
 
 Gross weight of transit packed securely for shipment in two boxes, about 50 Ibs. 
 
 Price of Small Complete Transit- Theodolite No. 4b, as de- 
 scribed above and shown in cut (with extra vertical wires if desired forstellarob- 
 servation) 
 
 Codeword, Gorastis. $315.OO 
 
 Extras to Transit No. 4b. 
 
 Compound centers made of steel running in sockets of cast iron to insure freest motion with 
 
 _ perfect fit . . . 20.00 
 
 Spirit level 4-inch with reversible clamp and tangent screw to telescope (see cut No. 4.) in ad- 
 ditions to level to vernier arm shown in the opposite cut 12.OO 
 
 Plain prism and colored glass ( Fig. 7, page 175) 8.OO 
 
 Split-leg tripod in addition to extension tripod (latter furnished with transit) . . . 16.5O 
 
 "Leather cover with shoulder straps 12. 5O 
 
 " " without " " . . 1O.5O 
 
 Hood to protect transit from rain and dust l.OO 
 
 Bottle of watch oil .... .35 
 
 * If desired, the U-shaped standard frame can be made of brass, weighing about 1 Ib. 
 more, no extra charge. If instrument is to be used near salt water, brass will prove 
 more durable for this standard frame, as aluminum and its alloys are apt to be affected 
 by salt water, saline and alkaline vapors and liquids. 
 
185 
 MERGER & SONS, 
 
 No. 4b. 
 
 (4 in. at edge of graduation.) 
 
 Small 
 Complete Transit- Theodolite No. 4bo 
 
 For size and particulars of this instrument, as well as for extras, see opposite page 
 
 Code word Gorastis. 
 
 For code words for Extras and changes from Gorastis 
 see pages F, O and H of complete code at back.) 
 
 Price, as above, $315.OO 
 
 Made to order only. 
 
 For a transit of a similar description but with a 4^-iiieh horizontal circle, 
 
 see next page, 
 
 >Iade to order only. 
 
186 
 
 4>4 " Complete Mine Transit No. 4k. 
 
 With Yoke Standards and Wye-Bearings. Without Compass. 
 
 For use where Transits sizes Xo. 2, 3 and 6 are considered too heavy and No. 4 anrt 4b 
 
 too light in weight. 
 
 The Transit shown in the cut on opposite page is best fitted for underground work 
 on account of its fully enclosed vertical circle. However, with a change from this lat- 
 ter type to any of our open forms of vertical circle, such as described and illustrated 
 on pages 155, 159, 193 and 200, this instrument is equally well adapted for engineer- 
 ing and surveying work of all kinds, and its price will be correspondingly lower. 
 
 The Yoke standard frame carrying the Wye-bearings, combined with the larger hor- 
 izontal circle, is of a type permitting of the placing of the plate levels of standard 
 length and character, in a manner more satisfactory than in the 4-inch Transit No. 4 
 described and illustrated on pages 182 and 183. This frame is of aluminum, and being 
 cast in a single piece, gives great lateral stiffness to the telescope and its attachments 
 and is leatherized or japanned as we deem it best. If desired, this frame can be fur- 
 nished in brass, when the weight of the instrument will be increased about one pound. 
 If the front plate level is desired to be in the center of the Yoke standards, as shown 
 in the cut of the Engineers 1 Transit No. 1m, then the height of the Yoke frame is 
 thereby raised ^-inch and the external shape of the latter will be like that illustrated 
 in No. 4 b Transit. The telescope reverses through the standards as usual. 
 
 Instead of three level ing" screws, this instrument can have four, when a reduc- 
 tion of 10.00 will be made from the price given below. 
 
 Made to order only. 
 
 Complete Mine Transit NO. 4k. As in cut, with three leveling screws. 
 
 SPECIFICATIONS : 
 
 Horizontal .circle 4%-inch (at edge of graduation), graduated on heavy inlaid ring of solid 
 silver; double opposite verniers read to minutes, two rows of figures to 360 in opposite direc- 
 tions; figures inclined in the direction verniers should be read, verniers at 30 to line of sight, 
 glass covered. 
 Vertical circle 4-inch, fully enclosed, edge graduation on solid silver, glass covered, 
 
 double opposite verniers read to minutes, figured from 0-90-0 and back. 
 Detachable reading glasses with reflectors for horizontal and vertical circles. 
 Compound centers bell metal. 
 
 Telescope iy 2 -incl\, objects inverted, aperture 1%-inch, poAver 18 dia. 
 Stadia wires, fixed, in ratio 1 : 100. 
 
 Spirit level 4%-inch, with clamp and tangent screw to telescope. 
 Plate levels of standard length and very sensitive. 
 Gradienter attachment. 
 
 Shifting center, to set instrument exactly over a given point. 
 
 Punch mark on top of telescope, to enable to center the transit from a point above. 
 Illuminator shade. 
 Extension tripod. 
 
 Instrument packed to stand upright in carrying case. 
 
 The mahogany case has a leather strap, hooks, etc. It contains a sun -shade, a wrench, a screw- 
 driver, an adjustable plumb-bob, a magnifying glass, an adjusting pin, and weighs about 5 Ibs. 
 Weight of transit about 5 Ibs. ; weight of tripod about 9 Ibs, 
 Gross weight of transit packed securely for shipment in two boxes, about 45 Ibs. 
 
 Code word, Grallus. Price, $336.OO 
 
 This transit with an open face graduation to the vertical circle 
 
 with double opposite verniers shown on page 155, but without reading glasses, 
 
 Code word, Grumla. Price, $316.OO 
 
 Extras to Transit No. 4k. 
 
 Center of steel running in sockets of cast iron, insuring freest motion with perfect fit . . 1818.0O 
 Striding level resting at points of contact in wyes as in No. n (applicable only when there is 
 
 no Style I interchangeable telescope ordered for this instrument) 22.OO 
 
 Iievel and spring tangent screw to vernier frame for the control of vertical angles as in 
 
 No. 4b, in place of the level to the telescope, no extra charge. 
 
 !Level and spring tangent screw to vernier frame in addition to fixed level to telescope, 1O.OO 
 
 Solar attachment with small telescope as on page 172 but with counterpoise .... 52. OO 
 
 Prism and colored glass (only plain form, Fig. 7, page 1 75, permissible) 8.OO 
 
 Short focus lens, pages 101, 203, one 8.5O 
 
 Patent interchangeable auxiliary telescope, style I, page 189* 37 .OO 
 
 Split-leg tripod in addition to extension tripod furnished with the transit 16.5O 
 
 Bracket in box, page 203 14.0O 
 
 Trivets, page 204 .... 
 
 Lateral adjuster and trivet combined for three leveling screws ; page 205 .... 36.OO 
 
 Leather cover with shoulder straps 13. OO 
 
 ' " without " " 11.OO 
 
 Hood to protect transit from rain and dust l.OO 
 
 Bottle of fine watch oil 35 
 
 * The post to which the auxiliary telescope attaches to the main telescope is shown in cut; but this post is 
 not furnished with instrument unless the interchangeable auxiliary telescope is ordered with the transit. 
 
187 
 C. L,. BERGEK & SONS* 
 
 No. 4k 
 
 in. at edge of graduation). 
 
 Patented. 
 
 Complete Mine Transit, No. 4k 
 
 With edge graduation and fully enclosed vertical circle. 
 
 For use in Mines and Tunnels. 
 
 Also for Bridge and Topographic work, etc., when provided with our open form 
 
 vertical circle. 
 
 (Fora front view of this instrument see colored illustration ) 
 
 For size, weight, particulars and extras of this instrument, see opposite page. 
 
 Code word, Grallus. 
 
 (For code words for Extras to Grallus, 
 
 see pages F and H of complete code at back.) 
 
 Price, $336.OO 
 
^ 188 
 
 t4 
 
 Mining Transits. 
 
 All of the foregoing instruments, particularly Nos. 2, 4V and 4 9 we recommend 
 2 for. general underground work. (The latter instruments chiefly on account of their 
 grea'ter portability and lightness.) The telescope may be either inverting or erect, 
 and may have a prism attachable to the ordinary erecting or inverting eye-piece to 
 facilitate sighting in inclined shafts. We frequently attach to the cross-axis a side 
 telescope, swinging free of the plates, of nearly the same length and power, which per- 
 5 mits of vertical sighting up or down a shaft (see pp. 93 to 95). We also furnish at- 
 ^ tached above and parpllel with the line of sight of the main telescope of Nos. 4, 4!, 
 5 and 6, another one of shorter length and lesser power mounted on a central pillar cast 
 on to the cross-axis of the main telescope, as in Style I. (See interchangeable auxil- 
 S iary telescope, pp. 189, 192, 193, 95 and 96.) 
 
 This latter telescope, which of necessity is of lesser power as compared with our 
 
 35 regular side telescope, will in most cases be deemed sufficient, as sights in mines are 
 
 short. Its power varies from 8 to 15 diameters, according as the telescope is erecting 
 
 * or inverting. We are, however, prepared to mount one of same length as our regular 
 ;J side telescope in cases where a complete revolution of cross-axis is not required. It 
 
 * will be seen that vertical sighting up or down a shaft can be done with ease and accu- 
 se racy, and this latest device has nearly all the advantages of a telescope mounted on in- 
 S, dined standards with none of its faults. When not in use the auxiliary telescope may 
 % be removed at will and stored in the box. As will be seen by reference to the descrip- 
 tion and cuts of this device, pp. 95, 96, and 189, the auxiliary telescope can also be 
 
 Sc readily attached to the end of the cross-axis of our Mining Transits Nos. 4, 4 1 /, 5 
 A and O when it becomes a side telescope. 
 
 The ready Intel-changeability from top to side makes the auxiliary telescope one of the most 
 ^3 desirable additions to a Mining Transit. 
 
 a To avoid errors in reading cardinal points, the compass ring is figured from to 360, the same 
 
 as the horizontal circle. Mining instruments should have large vernier openings to admit of as much 
 "3 light as possible, and all graduations should be on solid silver. For the illumination of the cross- 
 wires, a small reflector is sometimes placed in the center of the cross-axis of the telescope of our 
 ?3 larger instruments; but as in the smaller telescopes much light is being cut out by its use, we prefer 
 
 5 to attach a reflector shade in front of the object glass . 
 
 No. 5. Mining Transit. Dimensions as in No. 1 (unusually large size); 
 graduations on solid silver; verniers reading to minutes are provided with ground glass 
 shades; 5-inch full vertical circle with aluminum guard; spirit level, fixed stadia wires, 
 j- clamp and tangent screws to telescope; extension tripod, etc. Price, $26O.OO 
 
 y No. 6. Mining Transit. Dimensions as in No. 2 (customary size); 
 
 ~j graduations on solid silver; verniers reading to minutes are provided with ground glass 
 
 shades; 5-inch full vertical circle with aluminum guard; spirit level, fixed stadia wires, 
 
 1 clamp and tangent screw to telescope; extension tripod, etc. Price, $26O.OO 
 
 Extras to Mining Transits Nos. 4, 4!, 5, 6 and 7 
 
 6 Striding level (for description and illustration, see pp. 156 and 211) $20.00 
 
 * Stadia wires, fixed 3.00 
 
 * Disappearing cross and stadia wires for erecting telescopes (p. 190). Patented . . . 6.00 
 iff Gradienter attachment for Nos. 5 and 6 
 
 . Five-inch vertical circle provided with double opposite verniers (see p. 155) .... 20.00 
 
 2 Edge graduation for vertical circle with a double vernier at eye-end, which is glass-covered, 
 
 jS as in cut (p. 198) - - extra 35.00 
 
 Edge graduation for vertical circle with double opposite verniers (p. 198) extra 45.00 
 
 3 Patent short focus lens (pp. 103, 101). No. 1, $8.50; No. 2, $8.50; Nos. 1 and 2 . . . 16.00 
 
 '35 Reflector for illuminating the cross-wires 4.00 
 
 fl Aluminum guard to vertical circle .... 4.00 
 
 g Prism, attachable to eye-piece .... 
 
 * Detachable side telescope with counterpoise (pp. 189, 193) 
 
 " Patent interchangeable auxiliary telescope. Style I, described on p. 96 and shown on p. 193 37.00 
 
 53 Berger Solar attachment with small telescope (pp. 172-173) . . 52.00 
 
 <+ Arrangement for offsetting at right angles to telescope 5.00 
 
 .2 Quick leveling attachment for size No. 4, $20.00; for all other sizes 15.00 
 
 g Half-length tripod 13.50 
 
 Extra extension tripod 23.50 
 
 " split-leg tripod (see note to No. 3) 
 
 *** Plummet lamp (large size) . . . . . . . 10.00 
 
 =2 " " (small size) 8.00 
 
 *i Bracket in box, with strap, auger, and lever (Fig. I, on p. 203) 15.00 
 
 v Trivet (see p. 204) 
 
 !> Plumbing device for carrying a line down a shaft (p. 191), $3.00 each; per pair . . 6.00 
 
 Patent Lateral Adjuster (p. 191) 25.00 
 
 "d Large plumb bob, weight 4 Ibs., for use in shafts 7.50 
 
 r 9 Bottle of fine watch oil -35 
 
 ^ Silk bag, to cover transit 1.00 
 
 fe Leather case for No. 4, with or without shoulder straps 10.50 to 12.50 
 
 " " No. 6, " " " 13.00 to 15.00 
 
189 
 
 Diaphragm showing ar- 
 rangement of wires as used 
 with our mine transits, to 
 distinguish center horizon- 
 tal wire from stadia wires, 
 to avoid mistakes. 
 
 Patented 
 
 Complete Mining Transit, 
 With Style 1, Interchangeable Aux- 
 iliary Telescope. 
 
 Size as in Nos. 5, 6, and 7. For a general descrip- 
 tion for Style I, etc., see pages 96-97. For 
 price and attachments, page 188. 
 
 NOTE. With the addition of the interchangeable auxil- 
 iary telescope as an aid to the customary mine transits, with 
 main telescope in the center of the instrument, the most diffi- 
 cult engineering problems in undergiound surveying become 
 at once very simple and -the results tbtained are as accurate 
 as those in surface work with its aid all sights in the verti- 
 cal plane are possible where the main telescope will fail, and 
 the vertical and horizontal angles can be measured with- 
 out an offset or corrections for excentricity caused by the 
 distance of the auxiliary telescope from the main telescope. 
 It is sufficient to remember, ivhen sights become inac- 
 cessible through the main telescope -when measuring hori- 
 zontal angles, to place the auxiliary telescope on top, and 
 when the same conditions prevail in measuring -vertical 
 angles, to place it on the side. 
 
 When the auxiliary telescope is detached, the transit is 
 just as serviceable for surface work as any other. 
 
 For use of the auxiliary telescope for astronomical ob- 
 servations, see page 97. For finding meridian with its aid 
 and the use of the solar, see page 71. 
 
 All our transits are provided with a fine punch mark on top of telescope to enable to 
 center instrument from a point above as well as from below . 
 
190 
 
 The 
 
 See M 
 Fig. 1. 
 
 Berger Patent Mine Tachymeter Nos. 4, 4 1 > and 6. 
 
 With Style I Patent Interchangeable Auxiliary Telescope (pages 97 and 193). 
 ming Transits, sizes 4 and 6, pages 97 and 193. For price of instrument and extras, see pages 
 
 182 and 188. 
 
 General arrangement of instrument showing upright post for auxiliary telescope, and a 
 reflector attached to object-glass. 
 
 Fig. 2. Interchangeable auxiliary telescope; Fig. 7 its counterpoise. 
 
 Fig. 3. Auxiliary telescope at side when measuring vertical angles', also for making latitude observa- 
 tions (see page 97), when sun is too high for observations with the main telescope. 
 
 Fig. 4. Auxiliary telescope attached to vertical post for use as top telescope when measuring steep 
 horizontal angles and when surface or meridian lines must be carried down a shaft wh^n 
 objects cannot be seen by main telescope, as well as for time observations when sun is too 
 high for observation with the main telescope. 
 
 Fig. 5. Side telescope placed parallel with the main telescope in emergencies by means of the strid- 
 ing level: also showing manner of centering from point above. 
 
 Fig. 6. Patent short focus lens attached to main telescope, p. 100. 
 
 Fig. 8. Patent Disappearing cross and stadia wires; inclined wires indicating center for stadia wires, 
 for erecting telescope, p. 122. Continuation on page 191. 
 
191 
 
 Fig. 9. 
 
 Leather ease with shoulder straps. For 
 prices see page 188. 
 
 Fig. 12. Plumbing Device A and B for carrying a 
 meridian or surface line down a shaft by 
 the plumb-line method.* Fig. 14. 
 
 Fig. 13. Lateral adjuster attached to tripod with 
 transit mounted upon it for ranging tran- 
 sit on to given line. For description and 
 method of application see page 205. 
 
 Fig. 14. Shows in graphical manner the method of 
 carrying a line down into the shaft by 
 means of the plumbing devices and lateral 
 adjuster. 
 
 * For valuable suggestions in carrying out the 
 perfection of this device we are indebted to Mr. 
 G. H. Potter, M. E., of Butte, Mont. 
 
 ftAN OF SHAFT AT COLLAR 
 
 13 
 
 VERTICAL SECTION THROUGH SHAF1 
 14 
 
 The Berber Patent Mine Tachymeter. 
 
192 
 
 Complete Mining Transit No. 6D, without Compass. 
 
 Shown with our Patent Interchangeable Auxiliary Telescope. Style I. 
 
 (See pages 95 and 96.) 
 
 Responding to many solicitations to make for mines containing magnetic ore, 
 or an electric plant, a transit similar in style and accuracy to our No. 11 (see page 
 180), we have designed the instrument illustrated on opposite page. It is light, 
 portable, and of the same size as our Nos. 4, 4 1 /4, 2 and 6 transits; but, owing to the 
 . . omission of the compass, the standards are cast in a single piece, affording greater 
 
 lateral stiffness, with increased capability to withstand rough treatment. It is, 
 adapted to all the complex conditions prevailing in underground work, and is very 
 simple in style and manipulation. It possesses all the advantages, as regards 
 accuracy of division, highest permissible telescopic power, and sensitive spirit- 
 levels of larger instruments. With the interchangeable auxiliary telescope added 
 for use in steep sighting, either on top or on the side of the main telescope, as 
 required, it becomes a most capable instrument for correctly solving what would 
 otherwise require special instruments and methods. When the auxiliary telescope 
 is detached, it is just as applicable to the common work in the mine or on the 
 surface as our regular engineers' and mining transits Nos. 4, 4 1 /, 2 and 6. 
 
 The U-shaped, standard frame of the telescope is made of aluminum, covered 
 with a fine dark Japan not affected by moisture; all other parts are finished in the 
 same manner as in our other instruments. The plate-levels are of our standard char- 
 acter and length, mounted directly upon the upper plate, where they are easily acces- 
 sible for the purpose of adjustment and ready observation, and are fully protected 
 from falling bodies. The principal plate-level is directly under the eye-end of the 
 03 " telescope. The two opposite verniers of the horizontal circle are in line of sight with 
 "3 So the telescope, and are protected from dripping water by cemented glass covers. The 
 
 circle itself is provided with two rows of figures from to 360, in opposite direc- 
 tions, with double verniers to correspond to them (unless otherwise ordered). The 
 M a & vertical circle, with figures from to 180, both ways from zero, has a double ver- 
 "2|^ nier, to enable the observer to read angles of elevation or depression with equal 
 
 S <s '* facility, and is provided with an aluminum protection guard, which carries the vernier 
 
 ^ ~o and also serves to readily adjust the latter to zero. Double opposite verniers can 
 
 -j T3 oo also be placed on the vertical circle, when the figures will run from to 90 each way 
 3 a ef'o and back to zero. The transit has inverting telescopes (unless otherwise ordered). A 
 O 'g c '-3 j| new and important feature of the instrument, which greatly increases its value, is this : 
 ^ I S+ 3 t ne ^ ne 9^ collimation of the main telescope is adjusted for distant, very near, and 
 J intermediate distances, by means of our recently patented device, to a nicety never 
 g c'^'g before attained; and no readjustment for near distances is necessary except after a 
 '-gji " severe accident. 
 
 g n ,2 The Style I interchangeable auxiliary telescope described on pages 95 and 
 
 ~ 96, and illustrated on opposite page, is non-adjustable, but it has been so much improved 
 .- "5 If g* that the line of collimation of its principal wire, which is the vertical one when used as 
 ^ '- o top telescope, and becomes the horizontal wire when used as a side telescope, lies so 
 "3 P u-, nearly parallel to that of the main telescope as to be practically correct in most cases. 
 -gja.g Weight of Mining Transit No. GD . 11 Ibs. 
 
 o> 53" .c 5 " auxiliary telescope and counterpoise, each 12 oz. . . \% 
 
 2^5 o^ " extension tripod . about 9 
 
 c O & i " instrument in mahogany box, with plumb-bob, sun-shade, 
 
 M&I)^H reading-glass, etc., etc. . about 22 
 
 Gross weight of instrument complete, packed securely for shipment in 
 S> 2 boxes . . .50 
 
 ^ No. 6D. Mining Transit without Compass, as in cut, with Style I 
 t JS Interchangeable Auxiliary Telescope. Horizontal and vertical circles, 5 inches; solid 
 S'is rjl silver graduations reading to minutes; ground-glass shades ; 5-inch level to telescope: 
 ^ $ ^ 1 2 plate-levels; inverting telescope, 10 inches long by iM-inch aperture; (if erecting, 
 S -g a 9% by 1 M inches) ; powers, 24 diameters; inverting auxiliary telescope Q l / 2 by 1 inch 
 5 8r aperture; (if erecting, 7 by 1 inch); fixed stadia wires; gradienter; 2 illumi- 
 ISgJ* nator shades; extension tripod, etc. Price, complete as above, $327.OO 
 
 ^ -g && Price, with double opposite verniers to vertical circle, extra, $ 5.00 
 
 b/D.= " prism attachment to eye-piece 8.00 
 
 g o> it it q mc k leveling attachment 10.00 
 
 '3 g " without Style I auxiliary telescope less, 37.00 
 
 " with one illuminator shade only for main telescope 4.00 
 
 Our Interchangeable auxiliary telescope, being of the most substantial construction 
 and character, may also l>e used for finding meridian and latitude when direct 
 observations cannot be made with the main telescope. See page 97. 
 
Interchangeable 
 Auxiliary Telescope. 
 
 Counterpoise. 
 
 Complete Mining Transit, No. 6 D, 
 
 With Patent Interchangeable Auxiliary Telescope (Style I.) 
 
|S 
 
 go Complete Wet-Mine Transit No. 6H, without Compass. 
 
 For sole use underground. 
 Shown with our Patent Interchangeable Auxiliary Telescope, Style 1. 
 
 This Transit is of same size and has the same characteristic features described 
 c under No. 6D, pages 192-3, with this difference, however, that it is specially de- 
 signed to meet the more exacting requirements existing in wet mines, with the object 
 of fully protecting the horizontal and vertical circles from dripping water, and also to 
 a certain extent from the action of fumes and gases, if used in coal-mines. To this 
 end the upper surface of the vernier plate of the horizontal circle is slanting down- 
 ward, the vernier openings are raised above the surface, arid special channels are pro- 
 vided so that the water will run off immediately. The same can be said of the verti- 
 . cal circle, as will be seen in the illustration on opposite page. In order to more fully 
 protect the main plate level from accidents, and to facilitate its reading from either 
 side of the instrument in the dark, it has been placed just below the telescope in the 
 center of the upper plate, and is fully protected by a guard. The yoke standard 
 frame has therefore been remodeled, and like its prototype No. 6D, page 193, is of 
 our most advanced design in this line, combining lightness with strength, beauty and 
 general adaptation to poor artificial light. The verniers are so placed that no shadow 
 can fall on and interfere with the reading of them in a faint light. The yoke 
 standard frame, as well as the casing surrounding the vertical circle and the upper 
 horizontal plate, is leather finished mine waters and acids do not affect it (see 
 page 9). 
 
 Owing to the limited distance between the standards and the larger space occupied 
 
 " by the wholly encased vertical circle, no stride or revolving cross-level can be applied 
 
 * to this instrument. The plate level in the center, however, is one of sufficient length 
 
 % Q and sensitiveness to insure a full control of the motion of the line of collimation in 
 
 m % < the vertical plane. The yoke standard frame enables to read steeper vertical angles 
 
 55 " So direct with the main telescope alone, thus often obviating the use of the auxiliary 
 
 Z?~* telescope. The whole instrument is of sturdy build, and therefore will withstand 
 
 3 JS -^ rough treatment. No water can come in contact with the vertical circle or verniers 
 
 ^ 'fi * as they are completely enclosed in a casing resembling a disc in form, thereby allow- 
 
 Q i -J2 ing all water to trickle off while in use, but when the instrument is carried on the 
 
 ^ "3 "3 tripod or in hand it should be so held that the front surface of the vertical circle 
 
 i ^ is tilted slightly upward. 
 
 ^ 2 TJ ,*5 Owing to this disc-casing this instrument is not so well adapted to surface work 
 'cs g where a strong wind pressure against the disc would produce vibrations of the instru- 
 3 g ^ ment and great liability to be blown over. However to meet a growing demand for a 
 f'| cs transit of type No. 6 H for surface as well as for mine work where conditions in 
 "g 3 ^ latter are more favorable we can attach in place of the fully enclosed vertical circle 
 > cf 8 anv one of tne other open frame protected vertical circles, see pages 193 to 200. 
 
 Made to order only. 
 
 gj 
 
 % Xo. 6H Complete Wet-Mine Transit without Compass, as in cut, but 
 o having only one double vernier to vertical circle at eye end, with style I. interchange- 
 a able Auxiliary Telescope. Horizontal and vertical circles, 5 inches; solid silver grad- 
 o nations reading to minutes; ground glass shades; edge graduation for vertical circle 
 fully encased ; 5-inch level to telescope; 2 plate-levels ; inverting telescope, 10 inches 
 ^ long by H-rnch aperture; (if erecting, 9| by 1 inches); powers, 24 diameters; in- 
 3 verting auxiliary telescope, 6 by 1 inch aperture; (if erecting, 7 by 1 inch); fixed 
 .. stadia wires; gradienter; 2 illuminator shades; extension tripod, etc. 
 
 * Price, complete as above, $352.OO 
 8 
 
 I D Price, with double opposite verniers to the edge graduations of the vertical 
 
 circle, extra, I 10.00 
 
 <.<. u flat glass covered graduation to vertical circle (in place of edge 
 
 graduation) with double vernier at eye end as shown on p. 199 350.00 
 
 * n i flat glass covered graduation to vertical circle (in place of edge 
 
 graduation) but with two double opposite verniers,see page 199 360.00 
 
 without style I. auxiliary telescope less, 37.00 
 
 o it t style I. auxiliary telescope but with provision for same, u 27.00 
 
 & n with one illuminator shade only for main telescope 4.00 
 
 For other Extras see page 188. 
 
 NOTE. Our Interchangeable auxiliary telescope, being of the most substantial 
 construction and character, may also be used for finding meridian and latitude when 
 direct observations cannot be made with the main telescope. See page 97. 
 
11)5 
 
 Complete Wet-Mine Transit. No. 6H. 
 
 For Price and Description see page 194. 
 
196 
 
 Different Types of Vertical Arcs and Circles 
 for Mine Transits, etc. 
 
 The regular arcs and vertical circles shown in the Engineer's and Surveyor's Tran- 
 sits No, Ib, page 153, No. If, etc., commend themselves for their simplicity of style, 
 accuracy of graduation and ease of reading. The latter 'feature is particularly well 
 attained in the above instruments where the double verniers are situated between the legs of the 
 standard, where they are well protected from injury and can be read simultaneously with the level 
 attached below. 
 
 In mines and underground work, where often the Transit must be set up in cramped places 
 and on stages erected in shafts, the difficulty of reading the vertical verniers without stepping aside, 
 or without shifting the horizontal plate, becomes apparent. To improve these conditions and in 
 order to obtain compactness the vertical arc in the older types of instruments, used extensively in 
 the coal mines of Pennsylvania, is permanently screwed to the side of the standard. It is of larger 
 diameter, and has a movable vernier arm. In other types the verniers are placed at the sides, as 
 exemplified in No. 6d, page 193, etc., or the graduations are placed on the edge of the vertical cir- 
 cle, which latter type embodies, however, a great deal of mechanical refinement. 
 
 All of these types have advantages and disadvantages, and therefore should be chosen simply 
 with a view to attain highest efficiency of an instrument intended for special work. It will hardly 
 be commendable to put the most refined style of vertical circle (requiring a more careful treat- 
 ment not to speak of its attendant greater cost to make and keep in repair) upon an instrument 
 intended for the more ordinary purposes, while in changed conditions all these refinements may 
 become necessary to obtain maximum efficiency under trying circumstances. 
 
 To enable to make the proper selection for the various instruments the different styles are 
 given below. 
 
 The Pennsylvania Arc. 
 
 This arc is of larger diameter than 
 usual but is not strictly of high accu- 
 racy. It differs from the regular arc 
 in that it is permanently screwed 
 to the standard, and that its movable 
 vernier arm can be readily set at zero 
 and clamped to the cross axis with the 
 telescope in any position, enabling to( 
 read vertical angles, plus or minus 
 from the horizontal plane to about 50 
 to 60 as well as to read also vertical 
 angles between any two points, when 
 by clamping the vernier arm at for 
 first point and then pointing the tele- 
 scope at second point the angle can be 
 read from of graduation. 
 
 This arc can be attached, without extra cost, to any Transit of size and style No. 
 1 and No. 2, in place of a regular arc enumerated with instrument. Made to order only. 
 
 Code Word. 
 Eleusine. 
 
 Movable Arc. 
 
 (Patented.) 
 
 This is an improved form over 
 the Pennsylvania arc in so far as it 
 is of more accurate design though 
 similar in manipulation. The arc 
 is screwed to a hub which is revolv- 
 able on the cross axis of the tele- 
 scope and is so arranged that the 
 
 hub can bt readily clamped with 
 
 telescope in any position and with- 
 
 out straining the arc. During non-use the arc can be clamped to the vernier frame and therefore, 
 unlike the regular arc, never projects above the standards when the telescope is in reversed posi- 
 tion. The vernier can be set to read zero by means of a tangent screw. 
 
 The mechanical arrangement of the various parts of this device is, however, more complicated, 
 as will be seen from the cut, and on this account it is not only more expensive to make but is mon, 
 liable to derangement as compared with the Pennsylvania arc or the regular arc (page 153) fixed 
 to the cross axis of telescope. Made to Order only. 
 
 Price extra (above price enumerated for regular arc) 
 
197 
 
 Code Word Beaman. NbiiliiM.Ji Price, extra, $3O.OO. 
 
 Made to order only. 
 
 See page 155. 
 
 The Beamaii Stadia Arc. 
 
 By means of this stadia arc there is determined rapidly and exactly the difference in elevation 
 between instrument and rod, and also the reduced horizontal distance to the rod, without the 
 measurement of an angle as such; without the use of either a vernier or a table, slide rule or diagram, 
 and with but trifling computation. 
 
 Stadia Arc. The Stadia arc carries two scales: 
 V. A multiple scale, used only for elevation determinations. 
 H. A reduction scale, used only to reduce inclined stadia readings to horizontal. 
 
 Index. Either scale is read by reference to an index adjusted to read the zero or initial point of 
 the scales when the telescope is level. This adjustment is carefully made by us and should remain 
 fixed. 
 
 Signs Proved. The initial graduation of multiple scale is marked 50 instead of 0, so that it* 
 direct reading will indicate, and the notes afterward prove, the sign of the angular value thereby 
 represented. 
 
 To obtain desired multiple, therefore, subtract 50 from multiple scale reading and use algebraic 
 remainder; e.g., if scale reads 56, multiple is 56 50 = +6. If the scale reads 47, multiple is 47 50 = 3. 
 
 The numeral 50 has been selected arbitrarily as a convenient one to use. 
 
 "Whole Numbers. A unique feature of the use of the multiple scale is that only such inclina- 
 tions of the telescope are used as will give a whole number scale reading, the fractional part of the 
 elevation being more quickly and accurately determined by a final rod reading. 
 
 There are upwards of 80 such graduations on the multiple scale (indicating multiples running from 
 +40 to 40). The process involves setting the telescope so far as to catch one of these even divisions, 
 thereby obtaining a whole number as a multiple and an easy multiplication. 
 
 Difference in Elevation Between Instrument and Rod. 
 
 Find such a whole number multiple arc setting (e.g., 55 or 42 set opposite index) as will throw 
 middle stadia wire somewhere on rod, it does not matter where. The arc reading, minus 50, when 
 multiplied by the observed stadia distance (in feet subtended) will give the exact difference in eleva- 
 tion to that height on rod which the middle stadia wire now happens to cut. This height on rod is 
 noted and allowed for as a final correction. 
 
 Reduction of Observed Distance to Horizontal. 
 
 The direct reading of the reduction scale, taken at the same pointing, gives the percentage of cor- 
 rection (always subtractive) necessary to reduce observed stadia distance to true horizontal distance. 
 This scale may be read to nearest division (per cent) or by estimation to any subdivision desired. 
 
 Illustration Suppose the observed stadia distance to be 6.40 (640 feet), and that the telescope 
 is afterward inclined so that multiple scale reads 33, at which arc setting the middle stadia wire reads 
 7.4 feet on rod. The multiple then is 33-50 = -17, and the computation for a foresight would 
 be 6.40X 17 = 108.8: and 108.8 7.4 = 116.2 feet = difference in elevation between instrument 
 and base of rod. 
 
 At above setting reduction scale would read 3 or 3%. Then 3% of 640=19.2 feet, and 840-19= 
 621 feet=reduced horizontal distance. 
 
 Difference in Elevation When Half Wire Interval is Used. 
 
 If, however, the half wire intercept must be doubled to read a long distance, it may happen that 
 no exact arc graduation setting can be found which will throw middle wire anywhere on rod. Then, 
 instead, make such even arc setting as will throw lower wire anywhere on rod. (Can always be done 
 if middle wire misses rod.) To height on rod thus cut by lower wire, add half wire intercept above, 
 which obviously gives height of middle wire on an imaginary extended rod. Then compute as usual. 
 
 Illustration If half wire interval is 4.2, the full distance would be 8.4 (840 feet). If multiple 
 scale reads 46 while lower wire cuts rod at 9.2 feet above its base, the computed middle wire reading 
 would be 9.2+4.2 = 13.4 feet. Then, with multiple of 4, compute as previously explained. 
 
:i98 
 
 Edge G-racl nation for Vertical Circle 
 
 Avith One Double A'ernier at 
 
 Eye-End. 
 
 In the Transits for underground work provided 
 with a full vertical circle it is often desirable to read 
 the angles from the eye-end of the telescope, to en- 
 able the manipulator "to secure all his observations 
 without stepping aside. The .Edge Graduation shown 
 here is in principle like that illustrated on Transit 
 No. Gd, page 193. The graduation is on the edge, 
 protected by an aluminum frame, and the double ver- 
 nier at eye-end is glass covered. The graduation is 
 on solid silver and reads to minutes. It is made in 
 a most substantial manner. In case of an accident 
 the cost of repairing is considerably greater than 
 that of the regular vertical circle. Made to Order 
 only. 
 
 Price of Edge-Graduation, as 
 shown in cut, with double ver- 
 nier at eye-end, glass covered, 
 (extra over price of Transits 
 Nos. 4, 5 and 6, enumerated 
 with regular full vertical circle) $35.OO 
 
 Code Word, 
 Heliotrope. 
 
 Price extra over price of instru- 
 ment No. 6d 
 
 25.OO 
 
 (Patented.) 
 
 Code Word, 
 
 Edge Graduation l^k^ililBfi^B F^^^F Hepatica. 
 for Vertical Circle 
 \vith Two Double 
 Opposite Verniers 
 
 This Edge Graduation 
 is like that described im- 
 mediately above, but has 
 two double opposite ver- 
 niers reading to minutes, 
 which makes it in prin- 
 ciple like Style O, page 155. 
 Made to order only. 
 
 Price of Edge Graduation, with two double opposite verniers, glass cov- 
 ered, (extra over price of Transits Nos. 4, 5 and 6, enumerated 
 with regular full vertical circle) $45.OO 
 
 Price extra for No. 6d . . . . 35.OO 
 
 (Patented.) 
 
 Berber Reading Glass and 
 Reflector with counter- 
 poise, for edge graduation 
 
 Price, $1O.OO 
 
 Same for double opposite ver- 
 niers 14.0O 
 
 Heralia. 
 Hestana. 
 
The Fully Enclosed Vertical Circle with Edge Graduation. 
 
 For Transits used only in Mines, Tunnels, etc. 
 Applicable to Transits No. 4, 5, 6D, 6H, and 7. 
 
 In distinction 
 fo the open 
 
 frame form of 
 the p r o te c t e d 
 vertical circle 
 shown in the 
 foregoing illus- 
 trations, designed 
 to offer the min- 
 imum resistance 
 of the exposed 
 
 area of a Transit to wind pressure and to pre- 
 vent the instrument from being blown over in 
 surface surveying, we recommend, where a 
 transit is used only underground, the fully 
 enclosed type to protect its graduations, as 
 in the horizontal circle, from dripping water, 
 and to a great extent also from fumes and gases exist- 
 ing in mines. The vernier frame shown in this cut is 
 therefore so constructed that it forms a shell without 
 any openings except those for the glass-protected ver- 
 niers. Two semi-discs, which can be easily removed 
 whenever desirable, fit into this v ernier carrying shell 
 at the back, thus encasing the vertical circle completely, 
 but allowing it to move freely with the telescope. No _ 
 water can penetrate inside this shell at any time while in use, nor when carried on its tripod or in hand, if 
 caution is taken to carry the instrument so that its front outside surface is slightly inclined in an upward 
 direction. Made to order only. 
 
 Price of vertical circle with edge graduation, as in cut, reading to 
 minutes, but with only one double vernier at eye-end, glass-covered 
 extra over price of Transits !N"o. 4, 5 and G, enumerated with 
 
 Code WovdB 
 
 regular full vertical circle 
 Price, extra over price of Transit No. 6D 
 
 $35.OO Hestard 
 25.OO Hestene 
 
 Price of vertical circle with edge graduations as in cut, with two 
 double opposite verniers, reading to minutes, glass-covered extra 
 over price of Transit No. 4, 5 and G, enumerated with regular full ver- 
 tical circle 
 
 Price, extra, for Transit No. GD 
 
 45.OO Hestite 
 35.OO Hestium 
 
 The Fully Enclosed Vertical Circle with the Customary 
 Face Graduation. 
 
 For Transits used only in Mines, Tunnels, etc. 
 Attachable to Transits Nos. 4, 5, 6, 6D, 6H and 7 
 
 In this type the regular ver- 
 tical circle and verniers with 
 a flat graduation (pages 155 
 and 193) are encased in a shell, 
 closed at the back by semi- 
 discs, to protect their gradua- 
 tion, from dripping water, 
 etc. In all other respects the 
 design is similar to that de- 
 scribed above for the edge 
 
 graduation: verniers are glass-protected and read t 
 minutes; glass shades if desired can be added. - 
 striding level to rest on special collars between stan- 
 dards, can be attached if desired, but only to Nos. 1 
 and 5 Transiis. Made to order only. 
 
 Price of vertical circle with a flat grad- 
 uation as in cut, but with only one 
 dou b le vernier at eye-en d , glass-covered, 
 extra over price of Transits Nos. 4, 
 5, G and 7, having regular full vertical 
 m circle (see page 196) $3O.OO 
 Price extra over price of Transit 
 
 No.GD . . . . 15.OO 
 
 Patented. 
 
 Hestmos 
 Hestnia 
 
 Price of vertical circle as in cut, with 
 two double opposite verniers, glass 
 
 covered, extra over price of Transits Nos. 4, 5, G and 7, having regular 
 full vertical circle, $4O.OO Hestota 
 
 Price extra for Transit No. GD 25.OO Hestra 
 
The Open-Frame Protected Vertical Circle with the Customary 
 
 Face Graduation. 
 
 For Transits used in Surface and Mine Surveying. 
 Attachable to Transits sizes No. 1, 2, 3, 4, 5, 6 and 7. 
 
 The aim of this device, which is 
 similar to that of our glass-protected 
 edge graduation with open frame, 
 page 198, is to place the same re- 
 finement, as regards protection from 
 dust or water, upon the vertical grad- 
 uations, as with that on tho horizontal circle, 
 when such is desirable for the highest class 
 of work. All of these devices tend to increase 
 the efficiency and life of a graduation, but 
 at the same time complicate an instrument 
 and add a little to the weight c-f the upper 
 part. Made to order only. 
 
 Price of protected vertical circle 
 with open frame, as in cut, but 
 with only one double vernier reading to minutes at eye-end, glass-covered, see 
 Heliotrope page 198, extra over price of Transits enumerated with full 
 vertical circle, size Nos. 1, 2, 4, 5 and 6 $3O.OO 
 
 Price extra over Mining Transit No. 6D 15.OO 
 
 Price of protected vertical circle as in cut, with tico double opposite verniers, glass- 
 covered, extra over price of transits Nos. 1, 2, 4, 5, 6 and 7, when enum- 
 erated with a regular full vertical circle . $4O.OO 
 
 Price of protected vertical circle with open frame as above, extra for Transit 
 
 No. 6D 25.OO 
 
 Price of reading-glasses if desired for double opposite verniers, extra 1O.OO 
 
 Code word* 
 Hestula 
 
 Hesmlil 
 
 Hesudra 
 
 Hesydo 
 Hetarda 
 
 The Level to the Vernier Frame of Protected Vertical Circle. 
 
 This feature, which greatly facili- 
 tates the reading of vertical angles 
 without requiring the instrument to 
 be leveled up accurately, can be added 
 to any of the foregoing styles of pro- 
 tected vertical circles, when so ordered 
 with instrument. 
 
 As will be seen, the level is placed upon 
 the vernier frame, which latter has a spring 
 tangent screw by which the bubble can be 
 readily brought to the center of its tube. 
 When properly adjusted to the instrument, 
 the bubble is required to be in the center 
 when the zeros of verniers and vertical circle 
 are in coincidence, and when the telescope 
 is in a horizontal position. 
 
 Made to order only. 
 
 Price of level w ith tangent screw attached to any of the foregoing protected vertical 
 
 circles, extra $12.OO Hetesy 
 
201 
 
 Stride Levels 
 
 Resting on Special Collars between the Standards (pages 148 and 149). 
 If desired, a stride level resting on special collars between the standards, so as to 
 revolve with the telescope, can be attached to Mine Transits Nos. 5 and O only, if 
 latter are not to be provided with a central post for style 1 or 2 interchangeable 
 auxiliary telescope. This stride level cannot be attached to any instrument already 
 made such Transits must be specially made. Price extra $2O.OO 
 
 If a stride lev el of the above kind is to be attached 
 to Mine Transits Nos. 5, 6 or 7, having style 1 or 2 
 interchangeable auxiliary telescope, then the arrange- 
 ment of the central post and stride level will he as 
 shown in the annexed cut, shown also on page 209. 
 
 Made to order only. 
 
 Price, extra, $3O.OO 
 
 NOTE. A stride level resting on special 
 collars cannot be attached to Transits size 
 Nos. 4, 6D nor OH. 
 
 For adjustment of this stride level of improved 
 form, see page 56. 
 
 Patented. 
 
 The Revolving Cross-Level for Mine Transits. 
 
 This is a very ingenious device to con- 
 trol the line of collimat'on of the telescope 
 at any altitude, in place of the stride-level, 
 but owing to the limited distance between 
 the standards, and the short distance be- 
 tween them and the vertical circle, it can be 
 applied only to our Mine Transits Nos. 5 
 and 6; or to No. 6D if latter is provided 
 with an open vertical circle of style shown 
 on page 193. 
 
 Unlike the regular detachable stride- 
 level, this cross-level is permanently mounted 
 upon the telescope's axis cf revolution by 
 means of two adjustable uprights. Its advan- 
 tages that itis revolvable between its uprights, 
 and therefore enables to watch the bubble 
 in very steep sighting. We recommend it 
 only in cases where a regular stride-level 
 cannot be applied owing to size and style 
 of instrument, and where it is considered 
 that some form of stride-level is a necessary 
 adjunct to a Mine Transit. The adjustment 
 of this device is somewhat more compli- 
 cated than that of the ordinary stride-level (in comparison with which it is also ot a some- 
 what minor degree of accuracy), but by the aid of the instructions given below it can be 
 made at any time, if required. Made to order 011 i y . 
 
 Patented. 
 
 Code, Hetica 
 
 Price, $35.OO 
 
 Adjustment of the Revolving- Cross Level. 
 
 To make the adjustment of the revolving cross lei'el, level up the instrument approximately, place its supporting 
 arms vertical and bring the bubble of the revolving level to the center of its tube by the instrument leveling screws, 
 and clamp horizontal plate. Now first verify the lateral adjustment of the revolving level by turning it on its axis 
 some 20 to 30 each side of the vertical. If this adjustment is made properly the bubble will stay in the midd e 
 of its tube. If not, make it so (as in a Wye Level) by the two capstan-headed screws at the side of the revolving 
 level. 
 
 Revolve the telescope 180 on its cross axis, turn the revolving level face up again, and see if also correct. If 
 not, remove half the error by the vertical capstan-headed screws of the revolving level tube and half by the vertical 
 capstan-headed screws of the supporting arm (this latter must be done in order to also adjust the revolving level 
 simultaneously to the telescope's horizontal axis of revolution) and then repeat, if necessary. 
 
 This being done, place the supporting arms horizontal and also make the adjustment of the sup- 
 porting am at 90 degrees to the former adjustment by the other pair of capstan-headed screws of the 
 supporting arm and then revolve the telesco->e 180 to see if correct, and repeat this adjustment if necessary. 
 
 These adjustments being made, it is well to repeat all of them in the above succession until perfected. When 
 this is accomplished, it will be necessarv to make the adjustment of the standard?, so that the telescope's axis 
 shall be truly at rieht angles to the vertical axis of the instrument: in other words, that the line of collimation travel 
 in a truly vertical plane. This can be done and verified by simplv turning the instrument 180 on its vertical 
 center and removing half the error, if anv. by the leveling screws and the other half by the raising or lowering, 
 as the case mav be, of the vertical adii'stine srrews provided on one of the standards. 
 
 On the whole, it is a somewhat delicate adjustment to make, renuiring some patience, and is best performed 
 on a window-sill. When properly performed it is just as likely as permanent as that of the plate or a stride-leveL 
 
202 
 
 C. L. BEKGKK & SONS. 
 
 Flexible Jointed Ann with Magnifier 
 
 Attachable to Any of Our Transits for Keadiiig the Vertical and Horizontal Verniers 
 
 Code Word 
 
 Price, $7.5O 
 Hetide 
 
 The Adjustable Center 
 
 On Top of Transit Telescopes used Underground!, 
 
 Our transits are made mechanically so perfect 
 that the fine punch-mark provided on top of the 
 telescope, to enabl to center the instrument from a 
 point above, is seldom more than one to two hun- 
 dredths of an inch from the true center, without 
 any other device, and is generally considered suffi- 
 cient. But for cases where even this small eccen- 
 tricity is objected to, in mine and tunnel engineering 
 of a very precise character, we have devised ac 
 adjustable center, as shown in cut, to be attached 
 to the post (or if there is no post, to the top of the 
 telescope's axis, if same has been originally provided 
 with a stud to receive it when being made) by means 
 of which the center can be adjusted to be correct, enabling to set up the instrument undei 
 a given point so that the prolongation of the vertical axis of revolution of the transit be 
 truly in line with the plumb-bob hung from a point above, thus leaving nothing to be 
 desired. This operation can be very much simplified by the use of our lateral adjuster, 
 see page 205. When not needed, the adjustable center can be unscrewed and screwed 
 in the box. If a top telescope is to be used, the transit proper should first be set up 
 correctly under the given point. This done, the adjustable center can be removed and the 
 top telescope screwed in its place. This device once properly adjusted to its transit by us 
 does not require any more attention in the future, unless the instrument should meet 
 with an accident, such as bending of the standards, or of the telescope's axis, etc., when 
 naturally, after it has been repaired, this adjustment of the centering device must again 
 be made. 
 
 Patented. 
 
 Price of adjustable center 
 Code word 
 
 . $3.5O 
 . HetiUo 
 
The Berger Bracket for Transit or Level. 
 
 This bracket is designed for supporting the instrument under conditions when the 
 use of even our extension tripod is inadmissible, and will be found a valuable auxiliary 
 for mining work. The instrument can be screwed upon the bracket, as on a tripod, and 
 the transit can be centred above or below a given point. The bracket is made of brass, 
 so fashioned as to offer the greatest rigidity, and is furnished with an auger and a lever. 
 Price, One bracket made for Transit No. 4, with four leveling screws in 
 
 box, with auger and lever " $14.00 
 
 One bracket made for Transit No. 6, as above . . . . 15.00 
 
 Every additional bracket extra, for either size . . . . 9.00 
 
 Price of Bracket as above (but for instruments with three leveling 
 screws size No. 5 and 6) with instrument fastener and lateral motion 
 packed complete in box with auger, etc 26.00 Hilgrim 
 
 Price of Bracket for transits with three leveling screws size No. 4 and 
 
 4 inch 24.00 Hilitos 
 
 Short Focus Lens Attachment. (For extended description see page 100.) 
 
 The above cut of our wye level and Fig. II illustrate our patented Focus Lens 
 Attachment, attachable to the object end of the main telescope, which permits the 
 focusing of objects nearer than the range of the main telescope will permit. As a rule 
 the main telescope can be made only to focus objects five to six feet distant from 
 instrument. These lenses are generally furnished in pairs. Lens No. 1 will permit 
 focusing of objects about 4 feet from instrument. Lens No. 2 will permit focusing of 
 objects about 2 A- feet from instrument ; used together they permit focusing of objects 
 about two feet from instrument. 
 
 The lenses are adjustable to the line of collimation of the main telescope and per- 
 mit of a high degree of accuracy. They will often prove of great convenience as an 
 auxiliary to view objects that are too near for observing without them. Attachable 
 to transits Nos. 1, 2, 3, 4, 5, 6, and to our wye and dumpy level. 
 
 Price. Lens No. 1 $8.50 
 
 2 . 8.50 
 
 *' Lenses " 1 and No. 2 ... 16.00 
 
204 
 
 Style of trivets used with transits and levels having 
 four leveling screws. (Also for use with lateral 
 adjusters, see page 205.) 
 
 
 44 
 
 s =3 *> 
 
 
 
 <L ** 88 
 
 
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 ^ ^ ^. ^ ^ ^. 
 
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 7 
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 :' I !^ :.= ^ 
 
 S 
 
 H 
 
 id Transits with FOUR levelin 
 
 be ordered for instruments with c< 
 sidered of no importance, at a pric< 
 sad receiving Hie instrument and tli 
 h trivet. In ordering trivets for 
 
 
 rtable) for transit No. 4 
 ansit No. 4 
 rtable) for transits No. 1, 2, 3, 5, 
 x>r Wye and Dumpy Levels 
 , but of longer radius. . . . 
 transits No. 1, 2, 3, 5, 6 and 1 
 1 Dumpy Levels 
 ;extremely high and heavy for use 
 lel operations) for transits No. 1, 
 1, also for Wye and Dumpy Lev. 
 
 
 3 
 
 sill 
 
 
 o-So^S^c i a* 
 =^ ftg a c S 1 S-- 
 
 
 iting Levels 
 
 i trivets shou 
 ien latter is c 
 > of iron the 1 
 nished with 
 
 
 >? >* * =^ i 
 S > 5< <> '^.r 
 
 Iflsgl^if* 
 
 alsia^sl^ 
 
 sts 8 ^,!* 05 
 
 fa 
 
 S 
 
 1 III 
 
 1 ?a 
 
 h and very h 
 instrumen 
 y Levels 
 eavy see small 
 center, but with 
 ye and Dumpy 
 
 ^ ^^ s- 3 ^> 
 
 * g'SS-c-5^ 
 
 9 i ? 5 s a fa 
 
 eft-hand cut above 
 sllifting center, bu 
 ly for Wye and D 
 ecota, but low a 
 
 d cut without sh 
 t fastener, only fo 
 
 all l 
 out 
 , on 
 To 
 ha 
 m 
 
 pq M 
 
 igh 
 nstru 
 
 ting center and instrument fastener, for center- 
 e transit above or below a given point as in 
 l right hand cut, but with high legs and very 
 y for transits No. 1 f, No. g and No. 11 
 
 ^ p ^ '5 ^3 
 
 en latter is provided with tree l 
 for Wye and Dumpy Levels 
 Topemus, but of iron (shifti 
 rument fastener of brass) 
 Topemus, but low and very he 
 Topesum, but of iron 
 
 if!!!!!!!!? 
 
 f III 
 
205 
 
 Patented. 
 
 The Berger Lateral Adjuster 
 
 For Transits with FOUR leveling screws.* 
 For use on tripods aiicl trivets. 
 
 The Lateral Adjuster shown above is an attachment, made of brass, separate from 
 the Engineers' Transit and its tripod. It screws to the tripod and then the instrument 
 is screwed on top of it. It is designed to range the line of sight of a Transit after 
 it has been leveled up, quickly and accurately onto a given line which may be indi- 
 cated by the plumbing wires A and B in a shaft, as shown in a graphical manner on 
 page 191, or onto a line given by any two station points in a tunnel or in surface 
 work, without disturbing the position of the level bubbles. 
 
 Being primarily intended for underground work the indicator wheel of the feed 
 screw may serve as an aid in moving the instrument a required distance in the dark 
 in ratio of hundredths and thousandths of a foot. 
 
 TO OPERATE THE LATERAL ADJUSTER. Screw it firmly to the tripod 
 and also attach Transit to it. Place both index marks of the Lateral Adjuster in 
 coincidence, and also place Transit about in the center of its shifting motion. Then 
 place tripod firmly on the ground in such a manner that the longitudinal axis of the 
 Lateral Adjuster is approximately at right angles to the line given by the plumbing 
 wires A and B, and at the same time that the line of sight shall be as nearly in line 
 with these wires as possible. Now level up carefully and move the line of sight of teles- 
 cope on to wires A and B by the feed screw of the Lateral Adjuster until the inter- 
 section of the cross-wires of the telescope and both plumbing wires are contained in 
 the same vertical plane. When Trivets and Lateral Adjusters are ordered for old 
 instruments the serial number must be given. 
 
 Lateral Adjuster for transit No. 4 with four leveling 
 
 screws, see large cut above 
 
 This lateral adjuster provided with detachable trivet 
 
 Topadil, see page 204 2 Ibs. 
 
 This lateral adjuster provided with detachable trivet 
 Topalate 
 
 Lateral Adjuster for transits No. 1, 2, 3,5, 6 and 11, 
 
 see large cut above 
 
 This lateral adjuster provided with detachable trivet 
 
 Topana, see page 204 , 
 
 This lateral adjuster provided with detachable trivet 
 
 Topalis 4 Ibs. 7 
 
 This lateral adjuster provided with detachable trivet 
 
 Topaxset 6 Ibs. 
 
 This lateral adjuster provided with detachable trivet 
 Topazula 8 Ibs. 7 oz. 
 
 Lateral Adjuster and Trivet Combined f see small cut 
 above for transits Nos. 1, 2, 3, 5, 6 and 11 
 (when latter is provided with four leveling screws.). . 4 Ibs. 5 oz. 
 
 Lateral Adjuster and Trivet Combined, same as To- 
 pixdil but with an adapter for use with transit 
 No.4 
 
 Lateral Adjuster and Trivet Combined,! same as To- 
 pixdil but with instrument fastener for transits 
 Nos. 1, 2, 3, 4, 5, 6 and 11 with three* leveling 
 screws . . . 
 
 1 Weight 
 
 Price 
 
 Code Name! 
 
 S 
 li Ibs. 
 
 $25.00 
 
 Topexura 
 
 t 
 
 . 2 Ibs. 
 
 30.00 
 
 Topibus 
 
 . 4^ Ibs. 
 
 31.50 
 
 Topicomus 
 
 9 
 
 
 
 . 2 Ibs. 7 oz. 
 
 f 
 
 25.00 
 
 Topilera 
 
 . 4 Ibs. 7oz. 
 
 * 
 
 31.50 
 
 Topimot 
 
 4 11) G 7 07 
 
 qi Kf) 
 
 Topiris 
 
 t 
 
 . 6 Ibs. 
 
 
 O L .*J\J 
 
 33.00 
 
 Topisine 
 
 . 8 Ibs. 7 oz. 
 t 
 
 33.75 
 
 Topitel 
 
 I 
 
 4 Ibs. 5 oz. 
 
 30.00 
 
 Topixdil 
 
 t 
 
 411,0 K n ~ 
 
 qq on 
 
 Topodillo 
 
 1 OS. O OZ . 
 
 8 
 g 
 
 K 1-1. 
 
 Oo,Ov/ 
 qc nn 
 
 
 O IDS. 
 
 OD.UU 
 
 Topogony 
 
 * For transits with three leveling screws, see Tunnel Tripod with centering and aligning de- 
 vice, page 210. 
 
 tThis device is to be placed upon the regular tripod head of our transits Nos. 1, 2, 3, 5, 6 
 and 11, when these are ordered to be provided with THREE leveling screws, or it may be 
 used independently on a bracket. As will be seen above there is also provided on top the instru- 
 ment thread for attaching transits Nos. 1, 2, 3, 5, 6 and 11 having four leveling screws, so that all 
 the above styles and sizes of instruments having either three or four leveling screws may be used 
 interchangeably on this three-screw tripod. It is of great advantage when a variety of instru- 
 ments are to be used on the same work. 
 
200 
 
 Patented. 
 
 The Lateral Adjuster screwed to a Trivet 
 For Transits with FOUR leveling screws. 
 
 For use in Tunnels and Underground Work of all 
 
 kinds; also useful in tlie erection of long 
 
 Bridges, Factories and their 
 
 machinery equipment, etc. 
 
 For Prices and Particulars of tliese auxiliaries- 
 see pages 2O4 and 2O5. 
 
207 
 
 The Berger Tunnel Tripod 
 
 Patented 
 
 \vitli Centering: ami Aligning Device for moving Transit with three leveling screws 
 under ov above a given point or onto a given line see cut of No. 1O b. 
 
 The above tripod has been designed to facilitate the placing of our Transits with three 
 leveling screws in the axis of a tunnel or onto a given line of sight. 1-or this reason, in addition 
 to our centering device, a lateral motion lias been provided, which allows the Transit to be moved 
 with ease and precision and without disturbing the position of the level bubbles mentioned in de- 
 scribing the Lateral Adjuster for transits with FOUR leveling screws, page 205. 
 
 This centering and aligning device is very simple to manipulate, but increases the weight of 
 the tripod-head, particularly when the latter is wholly made of brass Thus the tripod-head for si/e 
 No. 1 and No. 11 Transits is heavier by about 2% to 3 Ibs., that for No. 2 about 2 to 2% Ibs., and 
 for No. 4 about \ l / 2 to 2 Ibs., and in the case of No. 1O and 12 about 5 Ibs. 
 
 TO USE. First place the uppermost triangular shifting piece, upon which the instrument 
 rests, in the center of its motion, which is indicated by equal spaces all around it, and also place 
 the lateral adjuster, which is the lower slide, in the center of its range, indicated by two small 
 projections on the tripod head and S!OAV motion piece of the lateral adjuster. 
 
 Then place the tripod head in such a position that the motion of the Lateral Adjuster is 
 about at right angles to the line of sight; after which level up, and center over or below the given 
 point; then clamp the large winged central nut in the usual manner and apply a slight pressure 
 by turning milled headed nut which acts against the spring of the instrument fastener. The in- 
 strument is now ready for angle work. 
 
 TO USE THE LATERAL ADJUSTER FOR ALIGNMENT. Clamp the milled 
 headed screAV on top, bearing in mind that, in order to enable the feed screw to move the instru- 
 ment during this lateral motion, loth the large iringed central clamping nut on top of tripod and fastener 
 spring below must first, be released. 
 
 'Inasmuch as the pitch of the feed screw corresponds to tenths of a foot, each motion of a 
 tooth of the star indicating wheel corresponds to a thousandth of a foot. Thus it will be seen that 
 if the pointing of the telescope on a distant scale requires the instrument to be moved I/ 1000th or 
 5/1000ths of a foot, as the case may be, that the manipulator turns 1 or 5 teeth around the index 
 mark and the object will be attained. When the line of sight of the telescope is in the given line 
 in the tunnel then slightly clamp the large winged central clamping nut on toi> of tripod and a^ain slightly 
 apply the .spring of the instrument fastener. 
 
 If in the course of operations the line of sight must be moved laterally, then the central 
 clamping nut and spring nut must again be first slightly released from the shifting piece before 
 any lateral motion should be attempted. 
 
 To use the tripod head as a trivet, unscrew the extension legs and screw the three 4-inch iron 
 legs in the places assigned them. It can then be used on brackets or any other special device 
 rigged up to receive it in the axis of the tunnel. 
 
 To obviate the removing of the legs so that attachment can he used as a trivet, a special 
 tripod head, having centering and lateral adjuster devices, but without wooden legs, may be or- 
 dered. This extra head complete would have the three 4-inch iron legs heretofore mentioned. 
 
 After the Lateral Adjuster has been used, before putting it away, it will be well to clean it, 
 placing the triangular shifting piece, as well as the lower slow motion slide of the Lateral Ad- 
 juster, again in a normal position, and then clamp both by the central clamping nut and small 
 knurled nut. 
 
 The tripod is made with fine mechanical nicety and should be well taken care of in order to 
 preserve it in good condition. 
 
 This device (for instruments with THREE leveling screws only) is made in four sizes as 
 follows : 
 
 For Transits No. 1, 5 and 11, .... Code Name Topoltuni 
 
 " Transits No. 2, 3 and (>,.... " " Topomara 
 
 " Transit No. 4 " Toponia 
 
 " Transits No. 1O and 12 Toposmus 
 
 The price of this lateral adjuster over the regular centering device furnished with our tran- 
 sit tripods will be given upon application. 
 
Mining Transit. 
 Interchangeable with Lamp Targets above Leveling Screws. 
 
 Telescope is mounted on standards as shown in cut of No. 3, with a double vernier 
 between the legs of the standard, and is provided with a striding level, see cut, page 156. 
 Compass Needle 3 3 /i inch. 
 
 The leading feature possessed by this instrument, as made by us, is that it can be interchanged 
 with the lamp targets above the leveling screws (see opposite page) so that after they have been set 
 up their relative position as to height and location will remain exactly the same upon being trans- 
 ferred from one tripod to another. It is an instrument especially adapted to the work of an engineer 
 in mines, and as such involves a great deal of apparatus not possessed by instruments intended for 
 surface work. Two lamp targets are commonly supplied with an instrument of this kind, but fre- 
 quently one only is ordered, according' to the character of the work for which it is intended. The 
 vertical centers of the lamp targets have to be well fitted into the sockets of the leveling heads, and 
 in consequence they cannot be furnished separately. The engineer will therefore decide whether one 
 or two lamp targets are necessary for this work. The lamp targets are of the same height as the 
 transit measured from the base above the leveling screws to the line of sight, and each is provided 
 with two spirit levels. The targets can be revolved in the vertical and horizontal planes. By means 
 of a tubular sight, situated on top of the target, the latter can be readily set in the direction of the 
 instrument so that its face will lie at right angles to the line of sight. The lamps can be raised or 
 lowered at will, and can be detached whenever necessary. It is of the bull's-eye pattern, and the 
 best lard-oil only should be burned in it. A disc of milk-glass placed between it and the target 
 furnishes an illuminated background, against which the intersection and outlines of the target are 
 seen sharply denned. Made to order Qnly> 
 
 Weight of Mining Transit No. 7, about 11 Ibs. 
 
 one lamp, " 
 
 Mahogany box containing instrument and one lamp, target, etc., about 32 " 
 one Extension Tripod, about 9 J Ibs.; two Tripods, " 19 " 
 
 Gross weight of instrument, complete, packed securely for shipment in 2 boxes, about 70 Ibs. 
 
 | [ Weight of Mahogany box, containing instrument only, about . . . . 22 Ibs. 
 
 S-aJ " " " 2 lamps, targets, etc., " .... 26 " 
 
 |51 " three Tripods, " . ... 28* " 
 
 alt \ Gross weight of instrument, complete, packed securely for shipment in 3 boxes, about 120 Ibs. 
 
 No. 7 Mining Transit, size as in Transit No. 6, but with one lamp 
 target as shown on opposite page; graduations on solid silver; verniers reading to 
 minutes are provided with ground-glass shades; 5-inch full vertical circle; aluminum 
 guard; spirit level, clamp and gradienter screw to telescope; illuminator shade; 
 striding level and fixed stadia wires, telescope mounted as shown on page 156, 2 ex- 
 tension tripods, 2 plumb bobs, etc. Lamp target packed in instrument-box. 
 
 Price, $38O.OO 
 
 No. 7a. Mining Transit, as above, but with 2 lamp targets, both packed in 
 separate box, 3 extension tripods, 3 plumb bobs, etc. Price, $4GO.OO 
 
 Mining Transit No. 7b. with Yoke Standards. 
 
 No. 7b. Mining Transit, as shown hi cut, with yoke standards, compass 
 with 2^-inch needle; 5-inch fully protected vertical circle with face graduation; 
 double opposite verniers reading to minutes, glass covered; interchangeable auxiliary 
 telescope, Style I; striding level; stadia wires; illuminator shade; gradienter; ad- 
 justable center for accurately centering instrument from a point above; one lamp 
 target packed with instrument in one box; two extension tripods; two plumb bobs. 
 Weight, size, etc., as above in Transit No. 7. Price, $492.OO 
 
 No. 7b. Mining Transit, as above, but with two lamp targets both packed in 
 separate box, three extension tripods, three plumb bobs, etc. Price, $ 572.OO 
 
 For price of extra attachments, see Extras to Mining Transits, page 188. 
 
 NOTE. To interchange the instrument and the lamp target proceed as follows: First withdraw 
 the spring bolt of the lower clamp for the outer center by means of the small milled-headed nut at the 
 end of the clamp opposite the tangent-screw. Then loosen the clamp screw immediately above the 
 leveling head. Now upon pulling back the spring bolt, situated at the side of the clamp, the instru- 
 ment or the lamp can be detached by lifting it out of the socket in the leveling head. These sockets 
 as well as the clamps, which serve to fasten the instrument or lamp target to the leveling head, 
 should be kept free from dirt or grit. After clamping the instrument to the leveling head, to pre- 
 vent any motion in its socket, and then releasing the small milled-headed nut from its fastening on the 
 spring bolt of the lower tangent-screw, the transit is ready for work and can be manipulated the 
 same as other instruments of our construction. 
 
 For adjustment of the transverse striding level, see page 56. 
 
209 
 
 Mining Transit interchangeable with Lamp Targets 
 above Leveling Screws. 
 
 Lamp Targets for Transits No. 7 and No. 7b. 
 
 Mining Transit No. 7b. 
 
 With Yoke Standards. 
 As made by C. L.. Berger & Song. 
 
 Patented. 
 
210 
 
 Tunnel Transits. 
 
 Xo. 1C a Tunnel Transit with four leveling screws and without lateral 
 adjuster, otherwise as enumerated below and shown on opposite page. 
 
 SPECIFICATION : 
 
 Horizontal circle 6^-inch, graduated on solid silver, double opposite verniers reading to 2O", 
 
 two rows of figures from 0-3GO. 
 Telescope 12-inch inverting, aperture 1%-inch, power 28 dia., telescope reversible over the bearings 
 
 as well as through the standard frame, reversible clamp and tangent screw. 
 Spirit level to telescope, 6-iiich. 
 Striding level resting on special collars, 3%-inch. 
 Stadia wires tixed. 
 Reflector. 
 Shifting center. 
 Standard frame of aluminium or brass, latter preferred on account of its greater resistance to 
 
 gases and fumes. 
 Kxtension tripod Made to order only. 
 
 Code word, Mobaco. Price, $292 
 
 No. lOb. Tunnel Transit as in cut, with three leveling screws ; tunnel tripod 
 with centering and aligning device. 
 
 SPECIFICATION : 
 
 Horizontal circle 6^-inch, graduated on solid silver, double opposite verniers reading to 2O", 
 
 two rows of figures from 0-360. 
 Telescope 12-inch inverting, aperture 1%-inch, power 28 dia., telescope reversible over the bearings 
 
 as well as through the standard frame, reversible clamp and tangent screw. 
 Spirit level to telescope, 6-inch. 
 Striding level resting on special collars, 4%-inch. 
 Stadia wires fixed. 
 Reflector. 
 Shifting center. 
 Standard frame of aluminum. 
 Extension tripod. Made to order only. 
 
 Code word Mobalis. Price, $342 
 
 No. lOc Tunnel Transit as in cut on opposite page and as described in No. 
 1Gb, but having an extension tripod with shifting" center only as shown 
 in No. llf. 
 
 Made to order only. 
 
 Code word, Mobatony. Price, $3O7 
 
 Extras to Tunnel Transit No. 1C a and No. lOb. 
 
 Lateral adjuster for transit No. 10 a with four leveling screws . . -$25.00 
 
 7-inch horizontal circle, double opposite verniers reading to 10 sec.,* extra. 30.00 
 5-inch full vertical circle, solid silver graduation, double opposite verniers 
 
 reading to minutes, as in cut, page 214 ....... 50.00 
 
 Reading glasses to horizontal circle , 15.00 
 
 Striding level resting at points of contact in Y's (instead of resting on spe- 
 cial collars as in cut) extra . 10.00 
 
 Aperture, 1^-inch instead of lf-inch, length of telescope 12 or 13^ inch 
 
 long, powers respectively 28 or 34 dia. ..... .10.00 
 
 Gradienter attachment ......... 5.00 
 
 Steel center running in cast-iron socket . 20.00 
 
 Extra extension tripod, with shifting center only, for transit having 3 level- 
 ing screws ............. 32.50 
 
 * Detachable reading glasses should always be ordered for a 10 ec. graduation. 
 For additional Extras to Tunnel Transits, see Extras to Mining Transits. 
 
No. lOb 
 Tunnel Transit 
 
 With three leveling screws mounted 011 tunnel tripod with Shifting Center and 
 Aligning Device. See page 2O7. 
 
 For Price and description of the above instrument, as well as list of extras, 
 
 see preceding page. 
 Codeword Mobalis. 
 
212 
 
 Triaiigulatioii Transit- Theodolites. 
 
 For use in Cities and in Bridge and Tunnel Construction, etc. 
 
 Since the introduction by us in 1875 of this style Transit with Yoke standard frame 
 cast in one piece and mounted directly on the top flange of the inner center, the de- 
 mand for them in all lines of engineering requiring high accuracy lias attained so great 
 a magnitude, on account of their excellence, as could not be foreseen at that time. 
 Many of these instruments are in use in the survey and triangulation of our largest 
 cities, and are giving great satisfaction. Many also have been supplied to Colleges and 
 are in use in State and Boundary Line surveys. 
 
 The great lateral stiffness attained by this form of standard frame enables to make 
 the trunnions of the telescope's axis cylindrical and to mount them in wye-bearings, 
 thereby securing to the telescope the most .accurate movement in the vertical plane 
 known. The telescope reverses through the standards as usual and over the bearings. 
 The trunnions are protected by dust-caps, and wherever possible capstan-headed 
 screws will take up any looseness between these dust-caps and the trunnions. 
 
 These Transit-Theodolites are made with three or four leveling screws. 
 
 No. 11. Plain Transit-Theodolite, with four leveling screws, as in cut, 
 on opposite page, but without level, clamp and tangent screw, vertical arc, or strid- 
 ing level to telescope ; in all other respects as in cut of No. 1 Ic. Specifications : 
 horizontal circle 6 finches, single opposite verniers, as in fig. 5 page 38, read- 
 ing to 2O", glass protected graduation and verniers, one row of figures to 360 
 clockwise ; 12-inch inverting' telescope, aperture 1^ inch, power 28 diameters, 
 achromatic eyepiece ; telescope is reversible over the bearings, as well as through 
 the standards ; long compound centers of hard bell-metal ; shifting center ; split- 
 leg tripod; aluminum standard frame leather-finished; mahogany box with 
 
 screw-driver, reading glass, adjusting pins, etc. 
 
 Made to order only. 
 
 Code word, Mobax 
 
 If instrument is desired with an erecting telescope of 24 diameters, add to code 
 word "erect." 
 
 \Veight of instrument, about 14 Ibs. Weight of tripod, about 10 Ibs. 
 Gross weight packed in two boxes, ready for shipment, about 60 Ibs. 
 
 Price of Plain Transit-Theodolite No. 11, as above, with four 
 
 leveling screws $225.OO 
 
 Extras to Plain Transit- Theodolite No. 11. 
 
 Three leveling screAvs with shifting: center (see page 52) . . - .15.00 
 
 7-inch horizontal circle reading to 10" by single opposite verniers, single 
 
 row of figures to 360 clockwise 30.00 
 
 Heading; glasses to horizontal circle (should always be ordered with instru- 
 ment reading to 10") 15.00 
 
 Reversible clamp and tangent screw to telescope, but without level to 
 
 latter 15.00 
 
 6-inch spirit level with reversible clamp and tangent screw to telescope . 30.00 
 3-inch striding level, as in cut, to rest on special collars to revolve through 
 
 the standards 20.00 
 
 5-inch striding level resting at points of contact in wyes, see page 214 . 30.00 
 
 5-inch vertical arc, as in cut on opposite page ....... 20.00 
 
 5-inch full vertical circle, (as in cut page 214) but with only one double 
 
 vernier reading to minutes at eye-end ; reversible tangent screw . . 45.00 
 5-inch vertical circle, see cut page 214, double opposite verniers reading 
 
 to minutes, reversible tangent screw ........ 50.00 
 
 3-inch level to vernier frame of vertical circle, see cut page 214 . . . 8.00 
 Two reading glasses to vertical circle, see cut page 214 . . =10.00 
 
 Stadia wires, fixed, ratio 1:100 .... . 3.00 
 
 Gradi enter screw . . . . . . . . . . 5.00 
 
 Center of instrument of steel running in a socket of cast iron, for instrument 
 
 with three leveling screws, having no compass 20.00 
 
 Oblong compass mounted on vernier plate at side of standard, with motion for 
 setting off the variation (three-inch needle reads only a few degrees each way 
 from zero) [For instruments with bell-metal centers only] ...., . 15.00 
 
213 
 
 No. 11C, Complete Transit-Theodolite with four leveling screws, (size 
 and particulars as described in Plain Transit-Theodolite No. 1 1 ) but with level, 
 clamp, and tangent screw, 5-inch vertical arc, striding- level, and 
 fixed stadia wires to telescope, as shown above. 
 
 Made to order only. 
 
 Code word, Mobaya. Price, $3OO 
 
 For Extras see list of Extras to Transit-Theodolite No. 11. 
 
214 
 
 No. lib. 
 
 Complete Double Opposite Vernier Attachment to 5-incb Vertical 
 
 Circle, with Level, Reading Glasses and reversible 
 
 Tangent Screw to vernier frame. 
 
 Attachable to Plain Transit-Theodolites No. 11, page 212 and lid. 
 
 NOTE. The telescope in the above cut has no level attached to it, as is frequently the case in 
 these instruments, and in consequence the vernier frame of vertical circle carries a 3-inch level by 
 which a complete control of the position of its verniers is assured when vertical angles are measured. 
 
 For price and particulars see Extras to Plain Transit-Theodolite No. 11, 
 page 212. 
 
 Triangulation Transit- Theodolite. 
 
 For use in Cities, by Colleges, and in Bridge and Tunnel Construction. 
 
 No. lid. Plain Transit-Theodolite with three leveling screws, as in 
 cut on opposite page, but without reading glasses to horizontal circle, also with- 
 out level, clamp, tangent screw, vertical arc and striding level to telescope. Yoke 
 standard frame is of aluminum and of pattern shown in No. llg. 
 
 Specifications : 
 
 Horizontal circle 6^-inch, single opposite verniers (as in fig. 5, page 38) reading 
 to 2O", glass protected graduation and verniers, one row of figures to 360 clockwise; 
 12-inch inverting 1 telescope, aperture 1^-inch, power 28 diameters, achromatic eye- 
 piece ; telescope is reversible over the bearings and through the standards ; long com- 
 pound centers of hard bell and phosphor bronze metal; shifting center (see page 52). 
 Mahogany box contains reading glass, screwdriver, wrench, adjusting pins, etc. 
 
 Made to order only. 
 
 Code word, Mobeda. 
 
 "Weight of instrument about 14 Ibs. 
 
 " *' tripod about I3 l / z Ibs. 
 Gross weight, securely packed in two boxes for shipment, about 60 Ibs. 
 
 Price of Plain Transit-Theodolite No. lid, with three leveling screws, 
 as described above $245.OO 
 
 For Extras to Plain Transit-Theodolite No, lid see Extras to Plain 
 TiAnsit-Theodolite No. 11, page 212. 
 
215 
 
 No. llf. 
 Complete Transit- Theodolite. 
 
 For use in Cities, in Tunnels, ami for Triangulation. 
 As made by C. L,. Berger & Sons. 
 
 Xo. llf. Size and particulars are in all respects like those desc: ibed under No. 
 11, page 212, and No. lid, page 214, but having three leveling screws, reading glass- 
 es to horizontal circle, level, clamp, and tangent screw, five-inch vertical arc, gradien- 
 ter, fixed stadia wires, and striding level to telescope as shown above. 
 
 Made to order only. 
 
 Codeword, Mobekia 
 
 Price, $343.OO 
 
 For Extras see Extras to Plain Transit-Theodolite, page 212. 
 
 (For Code "Words for Transit-Theodolite and P^xtras and changes see page J, 
 Complete Code at back.) 
 
210 
 
 No. 11 m. 
 7-iiich Complete Transit-Theodolite, 
 
 SPECIFICATIONS :- 
 
 No. 11 111 Transit-Theodolite as in cut 011 opposite page. 
 
 Horizontal circle 7-inch, single opposite verniers reading to 1O", one row of 
 figures 0-360 clock-wise, reading glasses to horizontal circle. 
 
 Vertical circle 5-inch, with one double vernier at eye end reading to single min- 
 utes, one row of figures from 0-90-0. 
 
 Level to vernier frame with reversible tangent screw. 
 
 Telescope 12-inch inverting, aperture 1^-inch, achromatic eye-piece, power 28 dia., 
 telescope reversible over the bearings as well as through the standard frame and 
 provided with reversible clamp and tangent screw. 
 
 Striding level at points of contact in wyes. 
 
 Stadia wires fixed. 
 
 Long compound centers of hard bell-metal. 
 
 Shifting center. 
 
 Standard frame of aluminum, leather-finish. 
 
 Split-leg tripod. 
 
 Instrument packs in one box of mahogany. 
 
 Made to order only 
 
 Weight of instrument about 14 Ibs. 
 
 " " tripod about 13^ Ibs. 
 Gross weight packed in 2 boxes ready for shipment, about 60 Ibs. 
 
 Code word, Mobeky Price, $385.OO 
 
 Extras to Transit- Theodolite No. 11 in. 
 
 Steel centers running in sockets of cast iron to insure freest motion 
 
 with perfect fit $20.00 
 
 Two double opposite verniers to vertical circle (as in cut page 214, in 
 
 place of one double vernier only at eye end) 10.00 
 
 Two reading glasses to vertical circle . <> 10.00 
 
 6-inch spirit level to telescope 16.00 
 
217 
 
 No. llm. 
 7-inch Complete Transit-Theodolite. 
 
 For use in Cities, Colleges, State ami Boundary-Line Surveys 
 For Size, Price and Particulars, see preceding page. 
 
218 
 
 No. llg, 
 7-inch Complete Triangulatioii Transit- Theodolite. 
 
 SPECIFICATIONS : 
 
 Xo. 1 Ig Transit-Theodolite, as in cut. 
 
 Horizontal circle 7-inch, one row of figures to 360 clockwise, single opposite 
 verniers reading to 1C". 
 
 Vertical circle 5-inch, open-form face graduation, glass protected verniers, one row 
 of figures to 360 clockwise, single opposite verniers reading to 30". 
 
 Level to vernier arm with reversible tangent screw. 
 
 Reading' glasses to horizontal and vertical circles. 
 
 Telescope 12-inch inverting, aperture 1^ inch, power 29 diameters, telescope re- 
 versible over the bearings as well as through the standards and provided with 
 reversible clamp and tangent screw. 
 
 Spirit level to telescope, 6-inch. 
 
 Striding level at points of contact in wyes. 
 
 Stadia wires fixed. 
 
 Gradienter. 
 
 Shifting center. 
 
 Standard frame of aluminum, leather-finish. 
 
 Made to order only. 
 
 Codeword, Mobello. 
 
 Price as above, $466.OO 
 
 This instrument with steel centers running in sockets of cast iron to insure freest 
 motion with perfect fit extra 2O.OO 
 
 Weight of instrument about 16 Ibs. 
 " " tripod about 14 Ibs. 
 
 Gross weight of instrument, complete, packed securely for shipment ; n 2 boxes, 
 about 60 Ibs. . 
 
211) 
 
 As made l>y 
 C. L. Berger & Sons 
 
 7-inch Complete Transit- Theodolite. 
 
 For use in Cities, Triangulation, Tunnels, Colleges and Boundary-Line Surveys. 
 
 For size, weight, particulars and extras of this instrument, 
 see opposite page. 
 
220 
 
 No. 12. 
 8-iiich Transit for Triangulation. 
 
 As made by C. L,. Berger & Sons. 
 
 No. 1 2. The form of frame chosen for mounting the telescope is similar to that in the 
 cut, which permits the reversal of the telescope through the standards as well as over the 
 bearings. It is of improved design and somewhat resembles that shown on page 219. It is very 
 stiff and very steady in strong winds, and being of aluminum, very light. 
 
 The inverting telescope has a clear aj)erture of 1 \ inches, focal length of 13J inches, power 
 28 to 32 diameters, reversible clamp and tangent; six-inch vertical arc graduated to read to 
 30* by a double vernier between the legs of the standard frame, figures run from to about 
 45 each way. The horizontal axis of the telescope is provided with a 4^-inch striding level 
 resting at points of contact in wyes. The horizontal circle is 8 inches in diameter, single op- 
 posite glass-covered verniers reading to 10", one row of figures to 360 clockwise, with 
 reading glasses. The radius of the three leveling screw-base is larger than usual, and as the 
 head of the tripod is proportionately larger, the instrument has great stability. It is provided 
 with a shifting center. The Yoke standard frame will be japanned or cloth finished, as we 
 deem it best. In this, as in all our instruments, the fine appearance and general character 
 depends principally on simplicity of design, coupled with fine workmanship, and a high state 
 of efficiency of every part. Other parts that cannot easily be finished and lacquered in the 
 usual but mostly antiquated manner, are therefore also treated in japan. 
 This is in line with good taste and modern thought and improvements, to enable us to unite 
 as many pieces as possible in one to secure great stability and steadiness under all conditions 
 in order to arrive at quick and thoroughly reliable results. Made to order only. 
 
 Weight of instrument, 18 Ibs.; weight of tripod, 19 Ibs. 
 
 Price .as above, $4O5.OO 
 
 This instrument without arc and clamp to telescope, less $35.OO 
 
 No. 12a Transit with a six-inch full vertical circle (instead of with arc as shown in 
 cut) vernier frame all open as in style No. lib page 214, single opposite verniers 
 reading to 30", one row of figures to 360 clockwise, reading glasses, level to vernier 
 arm $443.OO 
 
 No. 12b Transit with a six-inch vertical circle with protected open-form vernier frame, 
 face-graduation, single opposite verniers glass-covered, as shown in cut page 219, reading 
 to 20", one row of figures to 360 clockwise, reading glasses, level to vernier arm, 
 
 $473.OO 
 
 Illumination of Cross Wires by Mir- 
 ror, Electric Bulb and Dry Battery. 
 
 This feature with the battery attached to a 
 tripod leg is very convenient, but is open to the 
 objection that the small mirror* placed as it is in 
 the center of the telescope cuts out the best rays 
 of the object glass and at a point where they al- 
 ready considerably converge toward the eye piece. 
 For this reason the simpler form of attaching a 
 reflector in front of the object glass is generally 
 preferred for the smaller transits. 
 Price, when ordered with Transit Theodolites 
 No. 12 to No. 15 . . . $22.OO 
 
 * The mirror can be removed 
 minating purposes. 
 
 ihen not needed for illu- 
 
221 
 
 No. 12. 
 8-inch Transit for Triangulation. 
 
222 
 
 No. 15. 
 8" Alt- Azimuth. 
 
 SPECIFICATIONS : 
 
 No. 15 Alt- Azimuth, as in cut. 
 
 Horizontal circle 8", one row of figures to 360 
 clockwise, single opposite verniers reading to 5". 
 
 Vertical circle 7", open-form face graduation, 
 glass-protected verniers, one row of figures to 90 
 to 0, double opposite verniers reading to 10", red and 
 black figures. 
 
 Level to vernier arm with reversible tangent 
 screw. 
 
 Reading glasses to horizontal and vertical circles. 
 
 Telescope 12" inverting, aperture H", power 30 
 diameters; telescope reversible over the bearings, as 
 well as through the standards, and provided with re- 
 versible clamp and tangent screw. 
 
 Striding level at points of contact in wyes, 5*.long, 
 2 seconds of arc for 1 division of 2 millimeters. 
 
 Electric axial illumination, with reflector in 
 telescope. 
 
 Trunnions, Invar steel. 
 
 Diagonal eye-piece, power 39 diameters. 
 
 Centers of steel or bell metal. 
 
 "Wires, 5 vertical time wires, with interval of 10 
 equatorial seconds ; 2 horizontal wires closely spaced. 
 
 Ring on leveling piece, to lift instrument. 
 
 Tripod, full length, split-leg, "without shifting 
 center. 
 
 Standard frame of brass or aluminum, leather 
 finish. Made to order only. 
 
 Code word 
 
 Price upon application. 
 
 Weight of instrument about 27 Ibs. 
 of tripod about 17j Ibs. 
 
 Gross weight of instrument complete, packed 
 securely for shipment in 2 boxes, about 100 Ibs. 
 
223 
 
 No. 15 a. 
 Alt .-Azimuth . 
 
 Alt.- Azimuth, as in cut. Graduations of 5 1 A inch circles on solid silver, two 
 opposite micrometer-microscopes for each circle reading to 10", and by estimation 
 to 2". Botn circles can be shifted, so as to bring different parts of the graduation 
 under the micrometer-microscopes. The telescope islO inches long, has an aperture 
 of 1% inch and a power of 24 diameters. Telescope is provided with a level on top 
 and with 3 horizontal wires for leveling and for stadia measurements, and if desired 
 with 5 vertical wires for star observation. The telescope must be reversed in its 
 bearings by hand. Telescope axis is of hardened steel. The striding and microscope 
 levels read to 5" of arc. Two ordinary small levels attached to the instrument 
 serve to place it in an approximate horizontal position. Complete in box. 
 
 Price, as above, $58O.OO 
 
224 
 
 No. 15 b. 
 Alt .-Azimuth. 
 
 Alt. -Azimuth, as in cut. Circles 8 inches diameter, micrometer-microscopes 
 reading to 5 seconds direct, and by estimation to single seconds. Telescope, 1.6 in. 
 aperture; focal length, 16 J inches; power, 32 and 48. Telescope axis is of hardened 
 steel and balanced by friction rollers. Reversing apparatus. Complete in one box. 
 
 Price, as above, $92O.OO 
 This instrument without reversing apparatus, .... less, $100.00 
 
 15 C, Alt.-Azimuth, as in cut above. Circles 10 inches diameter, mic- 
 rometer-microscopes reading to single seconds direct. Every single degree figured. 
 Telescope, If-inch aperture ; focal length, 20| inches ; power, 40 and 60. Telescope 
 axis is of hardened steel and balanced by friction rollers. Complete in two boxes. 
 
 Price, as above, $13OO.OO 
 
225 
 
 Portable 2" Time Transit Instrument. 
 
 As made by C. L.. 
 
 Transit Instrument, as shown, has 2^" clear 
 aperture, by 24.45" focal length, with one Kellner 
 eye-piece power of 33 diameters and one large elbow 
 eye-piece of 30 diameters; there are 5 time wires, 
 spaced 20 seconds of time apart, and 2 closely 
 spaced horizontal wires; a reflector in the center of 
 telescope for illuminating the cross wires, and lard-oil 
 lamp is attachable to either side of standard frame. 
 
 The 6" aluminum vertical circle is graduated 
 on Sterling silver, has double opposite verniers read- 
 ing to minutes, with one row of figures from to 
 180 to for zenith distances; circle reading when 
 telescope points to the zenith; reading glasses are 
 attached, and a control level; it has a reversible 
 clamp and tangent. 
 
 The stride level has a value of 6 seconds of arc 
 for T Y' run, provided with an adjustable mirror for 
 reading the bubble. 
 
 The standard frame is provided with two level- 
 ing screws and one fixed point, with base plates. In- 
 
 Berger & Sons. 
 
 strument adjustable in azimuth by opposing capstan 
 screws on one base plate; finished in our handsome 
 leather finish. 
 
 The instrument is packed securely in two stout 
 wooden boxes, to withstand long transportation. 
 
 Weight of instrument complete, 130 pounds. 
 
 Gross weight packed for shipment, 260 pounds. 
 
 If instrument is to be used at several stations, and 
 it is desired to pack same to permit of ready trans- 
 portation from place to place, an extra charge for 
 this special packing will be made. 
 
 With rack motion for observing transit or stars, 
 
 Extra 
 
 For striding level reading to single seconds of 
 arc Extra 
 
 Filar micrometer, reading to single second of 
 arc Extra 
 
 Impersonal micrometer Extra 
 
 Prices upon application. 
 
Portable Transit Instrument for Latitude Observations. 
 
 As made by C. L. Berber & Sons. 
 
 No. 16. Aperture of object-glass 3 in.; focus 28 in.; spider-line or glass 
 micrometer ; micrometer screw reads to seconds of arc ; spirit-levels read to seconds 
 of arc ; diagonal eye-piece 80 dia. ; Ramsden eye-piece 40 dia. ; vertical circle 8 in. 
 India.; bell-metal pivots, two lamps and arms, adjustable reflector; reversing 
 apparatus ; two cases, enc. 
 
 Price $980. 
 
227 
 
 Portable Astronomical Transit Instrument. 
 
 As made for U. S. Lake Survey. 
 
 No. 17. Aperture of object-glass 3 in.; focus 39 in.; spider-line or glass micrometer; diagonal eye- 
 piece magnifies from 90 to 120 dia. ; Ramsden eye-piece magnifies 75 dia.; striding level reads to 
 seconds of arc; adjustable mirror to read the level from below; reserve level; pivots of hardened steel; 
 small adjustable plane reflector; two lamps and arms; reversing apparatus; two finding circles each 
 provided with double verniers; cast-iron frame rests on three leveling screws of steel, which are pro- 
 vided with foot-plates one of them is adjustable to set instrument- in the meridian; two cases, etc. 
 
 Price $13OO.OO 
 
 (Notice of this Instrument, with full description, in Johnson's New Universal Cyclopaedia, under 
 
 article "Transit.") 
 
 The above instrument provided with an Impersonal Micrometer, U. S. C. & G. S. Pattern. 
 
 Price on application. 
 
228 
 
 Reflecting Circle. 
 
 
 Artificial Horizon. 
 
 Mercury Horizon of boxwood, with silver-plated copper bowl; bottle of bo*' 
 od for mercury ; brass rectangular roof with glass coyers made of parallel glass. 
 All complete, packed In a box. Best quality, imported. . . Price, $5O.OO 
 
229 
 
 Sextant. 
 
 Sextant. Radius, 7 inches, 145 ; four sun-glasses between fche large and the 
 email reflecting mirror, and three sun-glasses behind the small reflecting mirror, all 
 of which can be turned on their axis 180; graduation on solid silver, reading to 10". 
 telescope f inch aperture ; two astronomical eye-pieces with powers of 6 and 10 dia. 
 One Galilean telescope with extra large objective* power 3 dia. ; one fixed raading 
 glass ; two sights for examination and correction of the large reflecting mirror. All 
 complete in box. Best quality, imported. . . Price, as above, $13O.OO 
 Sextant, as above. Radius 10 inches, all complete in box. . Price, 15O.OO 
 Pocket Sextant, best quality s 43.OO 
 
 Magnetometer, according to design Carnegie Institute, Dept. Terrestrial Mag- 
 netism. Price on application. 
 
 Pendulum Apparatus for determining gravity. U. S. C. & G. S. Pattern. 
 
 Price on application. 
 
230 
 
 Current Meters, 
 
 The types of current meters, as shown in Figs. I, II, and III, in our former Catalogues, have been 
 omitted, owing to the many improvements made and embodied in the Meter, as shown in Figs. IV, V, and 
 VI, this Catalogue. We are, however, prepared to make to order Current Meter No. Ill, as designed by 
 Mr. Clemens Herschel, if so desired. 
 
 Current Meter No. IV. 
 
 The electric form of meter shown in Fig IV is especially adapted for observations 
 upon large rivers, arms of the sea, etc. It has its registering apparatus above the sur- 
 face of the water, or on the bank of a river, and current measurements may be made 
 with it at any depth, and may be continued for a week, or longer, without stopping, if 
 desired. Half a dozen or more of these meters may be strung on one and the same ver- 
 tical rod or wire, and simultaneous observations then taken of the velocities at different 
 depths below the surface. 
 
 This form was used upon the gauging of the Connecticut River* by General Ellis, 
 and was designed particularly to avoid the catching of floating substances, such as 
 leaves and grass, upon either the vanes or the axis, and to render the record of the 
 instrument independent of the position of its axis with respect to the line of the current, 
 also, to get less friction upon the axis so as to measure low velocities accurately. 
 
 This current meter is constructed upon the principle of Robinson's Anemometer, turning by the difference 
 of pressure upon opposite vanes of the wheel. The vanes of this meter, however, instead of being hemispher- 
 ical cups with a straight stem, are made conical at the ends, and are hollow and taper to the central hub, so as 
 to offer no obstruction to the slipping off of straws, leaves, or grass, as the wheel revolves. The central hub 
 is made tapering, so that any object can slide off easily, and it extends over the joints at the ends of the axis, 
 so as to enclose and protect them from floating substances. The axis runs in iridium bearings. The forward 
 end of the frame which carries the wheel can be turned and secured in any position, so that the wheel can be 
 horizon tal/vertical, or at any desired angle. 
 
 The electrical connection is made by carrying an insulated wire from near the center of the instniment, 
 where the insulated wire from the battery is attached to it by a binding screw when in use, out to the end of 
 one arm of the wheel frame, where it ends in a fine platinum wire resting upon a ring in the hub of the whee^. 
 This ring is made of alternate interchangeable sections of silver and hard rubber, secured in place by screws, 
 so that their position can be changed to register whole or part revolutions as desired. There is also a socket 
 and set-screw in the body of the frame near the center, for the return current, which can be carried through a 
 plain wire slightly twisted around the insulated wire so as to form one cord. If the instrument is run upon a 
 wire, or has a metallic connection with the surface, the return current can be made through that. A better 
 method now in vogue is to use a " twin " insulated wire. 
 
 The universal motion at the center of the frame and the tail are of the usual construction. This meter 
 can be used in connection with any apparatus for registering the revolutions of the wheel by the breaks in the 
 electric circuit. 
 
 Price complete, as in Fig IV, with electric register and one battery 
 
 etc., packed in three cases, ........ . $195.OO 
 
 Price of this instrument without electric register and battery . . . 135.OO 
 
 * For further information on this point, see Gen'l G. K. Warren's Report of Surveys and Examinations 
 of Connecticut River. 
 
 We can have this meter, as well as Nos, V and VI, carefully rated at an additional expense of from 
 $15.00 to $25.00. Unless ordered otherwise, the instruments will be sent unrated. 
 
 Current Meters No. V and No. VI. 
 
 This form of Current Meter, invented by Fteley & Stearns,! and illustrated on page 
 198, is specially adapted for observations upon smaller rivers, streams, conduits, flumes, 
 
 etc. The 3% inch wheel has vanes of true standard screw pitch welded to the rim and 
 axle and is perfectly balanced. All edges are sharp to cut the water to avoid eddies. 
 Its axle is provided with points of iridium, so as not to be affected by grit in the water 
 and to run in the bearings with minimum friction. These points, combined with ac- 
 curate workmanship and good design, insure a permanent and unvarying rating curve. 
 
 The instrument is provided with a registering apparatus, the dial wheels of which 
 are completely protected by a glass cover readily removable at will. This counting 
 mechanism is operated by a string, by means of which the dial wheels are thrown in 
 and out of gear. One short pull throws them in and the next pull throws them out ; 
 next in, and so on. 
 
 Guards placed over this mechanism and the wheel protect them from injury and 
 floating substances. Those of the wheel are far removed from it to avoid checking the 
 flow of water. 
 
 For more extended observations upon rivers, etc., a separate electric register and 
 battery, shown on page 232, can be supplied with this instrument. 
 
 Price of Current Meter No. V, supplied only with the ordinary 
 registering apparatus, as shown in the main cut on page 232, and with 
 12 feet of brass tubing, made in sections of four feet, and graduated in 
 feet and tenths. Complete in two cases, ...... $135.OO 
 
 Price of Current Meter No. VI, in all respects similar to that above, 
 but in addition to the ordinary registering apparatus this instrument is 
 provided with an electric register, one battery and copper wire, as 
 shown in the smaller cuts on page 232. Complete in four cases, . . $195.OO 
 
 j- For further information on this Current Meter, read " Description of some experiments on the Flow 
 
 of Water, made during the Construction of Works for Conveying the Water of Sudbury River to Boston," by 
 . Stearns (Transactions of the Society of Civil Engineers, Jan.-March, 1883). Also, " On 
 , together with a Reason why the Maximum Velocity of Water Flowing in Open Channels 
 
 is Below the Surface," by F. P. Stearns; a paper read at the Annual Convention of the American Society or 
 
231 
 
 This meter can be arranged to reg- 
 ister single revolutions and every 5 
 revolutions. 
 Price, extra .... $15.OO 
 
 Current Meter No. IV. 
 
 As made by C. L. Berger & Sons. 
 
232 
 
 Current Meters No. V and VI, 
 
 As made by C. L.. Berger & Sons. 
 
 For price, etc., seepage 230. 
 
 This No. VI. meter can be arranged to register single revolutions and every 5 
 revolutions. Price, extra . $15.OO 
 
For the convenience of our customers we append a list of miscellaneous articles kept in 
 stock, but most of them are not of our manufacture. Those not made by us are of the best 
 quality obtainable, and the prices quoted are identical with those in the market. 
 
 Precision Pantographs. 
 
 The arms of these Panto- /"s^^mp^^Sf'lo graphs, to avoid friction on the paper, are suspended 
 from a solid iron support (as will ^HrlSw jlf!) be seen in cut), the latter being supplied with levels 
 and leveling screws. The instru- / I I ment is capable of enlarging or reducing in all ratios, 
 
 and is very useful for copying. The brass arms are hollow and square in cross- 
 
 section, and are divided to millimeters with verniers reading to -J^ mm. For the accurate setting of the 
 verniers slow motion screws are provided. All swivel pints turn upon center points. The disengaging mech* 
 anism is a special convenience. The ratios from | to ^7f are set with pole at end, those from 3 to T to jf 
 are set in the middle. The pole and pencil-holder are therefore interchangeable. 
 
 No. 99. Suspended Pantograph, arms about 24 inches long, in wooden case. 
 
 Price, as above, $15O.OO. 
 No. 100. Suspended Pantograph, arms about 38 inches long, in wooden case. 
 
 Price, as above $18O.OO. 
 
 NOTE. The Pantograph with 24-inch arms when set at 5 can circumscribe a ig-inch square, or an 
 oblong 155 x 24 inches, approximately. 
 
 The Pantograph with 38-inch arms can circumscribe a 3i-inch square, or an oblong 275 x 39 inches, 
 approximately. 
 
 Compensation Planimeter. 
 
 The compensation Planimeter illustrated above consists of two parts, which pack separately in the case, 
 the tracing frame and the pole arm. The tracing frame rests on 3 points, the measuring wheel, the tracer 
 point and the roller. A finely polished steel ball, fixed at one end of the pole arm, rests in an opening of the 
 tracer arm, forming a ball and socket joint. This joint forms the axis of rotation of the tracer arm. which by 
 means of the pole arm moves on a circle as guide line ; at the same time it enables the tracing frame always to 
 rest with its three points on the plan. The length of tracer arm is about 9 1-2 inches and pole arm 7 1-2 inches. 
 
 The pole consists of a brass cylinder attached at one end of the pole arm. Its lower surface forms an 
 edge at right angles to the pole arm, which by the rocking motion provided by this edge can be lowered until 
 its other end, which carries the ball, is firmly secured in the socket. In the center of this brass cylinder a 
 simll steel pin is inserted and kept" in place by a set screw. This pin terminates, at both ends in a finely 
 hardened point, one of which projects slightly under the lower edge of the cylinder. The tracer arm is pro- 
 vided with a vernier and micrometer screw by which it can be placed at any division mark on the tracer arm, 
 which is graduated throughout in 1-2 mm. The axle of the measuring wheel, ending in finely made pivots, is 
 of the be-*, hardened steel working in cylindrical steel point bearings. With tl e Planimeter is supplied a 
 proving bar, which enables by its graduations to describe several circles of known radii. 
 
 In using, place the Planimeter approximately in the center of the area to be measured, so that the plane of 
 the measuring wheel, if extended, passes through the pole. After obtaining the measurement by using the 
 Planimeter with the pole arm on one side of the tracer arm, the pole arm may be placed on the other side and 
 another measurement made. The mean of these two readings will eliminate any error ol the measuring wheel, 
 thus this form of instrument is a compensation Planimeter. 
 
 If the area to be measured is too large for the scope of the instrument it should be subdivided into smaller 
 areas. According to the importance of results to be obtained, one measurement may be sufficient around the 
 plan, but when very accurate results are desired it will be good practice to make 2 or 3 consecutive measure- 
 ments with the pole arm on one side of the tracer arm and afterward the same number of consecutive read- 
 ings with the pole arm on the other side of tracer arm, and by taking the mean of the averages of readings 
 obtained, very close results will be obtained. 
 
 The Compensation Planimeter is made of German silver and bronzed brass. 
 The tracer arm is adjustable and graduated to the end, pole weight of improved pat- 
 tern. Instrument complete in velvet-lined case, with table of constants for U. S. 
 standard measure, adapting it to any scale. 
 
 Xo. 107. Price complete as above . 3O.OO 
 
 "No. 108. " " " " when specially rated . . . 34.OO 
 
234 
 
 Plain Polar Plaiiimeter. 
 
 This Planimeter is of German silver, with adjustable tracer arm fully gradu- 
 ated, about 9 inches long, in polished mahogany box with proving bar. 
 
 Price of instrument when rated ... . . . $31.00 
 
 not rated but with all the improvements 27.00 
 
 Precision Plaiiimeters. 
 
 These Planimeters are very much more accurate than the ordinary Polar Plani- 
 meters. The graduated rollers do not touch the paper at all, but roll, instead, on a 
 hard, highly polished surface of steel, thus eliminating all errors due to the irregu- 
 larities of the paper surface. 
 
 No. 1O9. Large Suspended Ball Plaiiimeter. 
 
 Not kept in stock. 
 
 This instrument is capable of doing very accurate work. The tracer arm is 11| 
 Inches long, the pole arm is 6 inches long, and the diameter of the toothed circle on 
 the pole is 6 inches. The angular motion of the tracer arm is about 90. 
 
 Surfaces from 2 x 4 inches to 7 x 10 inches can be measured without moving the 
 pole. 
 
 Price of instrument complete packed in morocco box . . . $75.00 
 
 No. 11O. Large Rolling Ball Planimeter. 
 
 The Planimeter illustrated above is made of German silver and 
 bronzed brass, and enables to obtain results of greater accuracy than 
 any other Planimeter yet made, both on large and small surfaces The 
 tracer arm is graduated throughout and has a length of 12 inches which can 
 be increased by a lengthener to 22 inches. Its angular motion is about 00 
 Ihe two rollers are made of exactly equal diameters, ensuring a motion of the 
 instrument, as a whole, in a straight line. A surface of any length and a width of 
 20 inches can be measured with the 22 inch tracer arm. 
 
 Price of instrument, with testing bar enabling to check areas 
 of known radii, and table of settings, in velvet-lined morocco box 
 with lock 
 
 $9O.OO 
 
Surveyors' Pocket and Marine Compasses. 
 
 No. 115. 
 
 No. 112. 
 
 " 113. 
 
 " 114. 
 
 " 115. 
 
 " 116. 
 
 " 117. 
 
 " 117a. 
 
 " 118. 
 
 " 119. 
 
 " 120. 
 
 No. 117. 
 
 Pocket Compass, with folding sights, 2}4 inch needle, . 
 " 2)4 inch needle, Jacob Staff mountings, 
 
 $ 8.00 
 . 10.00 
 12.00 
 " with level, folding sights, 4-inch needle, with ball and 
 
 socket joint, 13.50 
 
 Vernier Pocket Compass, 4^ inch needle, " Tripod " and 2 levels . 23.00 
 Prismatic Compass, complete, with azimuth glasses, and divided alumi- 
 num ring, 3 inch Leather Sling Case. Best kind, .... 30.00 
 
 Hutchinsbn's Prismatic Compass bronzed, of improved pattern nearly 
 
 enclosed top, floating card dial, 2 inch, in morocco case 
 Pocket Compass, watch pattern, brass, 1> inches in diameter with 
 hinged cover and stop to needle, ... ... 
 
 Pocket Compass, gilt, watch pattern, with stop, enamelled dial and 
 
 agate centre ; 1 or 2 inches in diameter 
 
 Ritchie's Patent Liquid Compasses, of all sizes, from $33.00 to $35.00, 
 $45.00 and $55.00. 
 
 Miners' Compasses. 
 
 11.00 
 
 1.75 
 5.00 
 
 No.125. 
 
 No. 125. Miners' Compass, provided with stop and glass covers, for tracing 
 
 iron ore, 3 inch Norwegian needle, $16.00 
 
 ** 126. Miners' Compass, provided with stop and glass covers, 4 in. Nor- 
 wegian needle, . 20.00 
 
236 
 
 Leveling Rods 
 
 No. 145 
 
 No. 147 
 
 No. 150 
 
237 
 
 Leveling- Rods 
 
 The leveling' rods illustrated 
 
 are of best make and are 
 
 always carried in stock. 
 
 No. 145. New York Rod. 6 T " ff 
 ft. extending to 12 ft., reading by vernier 
 to lOOOths of a foot, with improved 
 mountings . . . $14.OO 
 
 No. 145 a. Extra Target for 
 
 N. Y. Rod for use with gradienter or 
 stadia measurements . . 5.OO 
 
 No. 146. Philadelphia Rod, 
 
 self reading, 7^ ft. extending to 13 ft., 
 reading by vernier to lOOOths of a foot. 
 
 14.OO 
 
 No. 146 a. Extra Target for 
 Philadelphia Rod . . 5.OO 
 
 No. 147. Boston Rod. 6 ft. 
 
 extending to 11 ft., reading by vernier 
 to lOOOths of a foot . . 14.OO 
 
 No. 148. Mining Rod. Philadelphia pattern 
 like No. 146, 6 ft 12.OO 
 
 Ranging Poles 
 
 No. 149 
 
 No. 148 a. Mining Rod. Philadelphia pattern 
 like No. 146, 3 ft. . . . . 12.OO 
 
 No. 148 b. Mining Rod. N. Y. pattern like 
 No. 145, 5 ft 1 2.OO 
 
 1 
 
 No. 148 c. Mining Rod. X. Y. Pattern like 
 
 No. 146, 3 1 , ft. 12.OO 
 
 
 No. 149. Flexible Self-reading Level Rod. 
 
 10 ft. long, 3 inches wide. This rod is graduated on 
 canvas and can be rolled up. When used it is fastened 
 upon a board with thumb-tacks . . . 3.25 
 
 No. 15O. Metric Level Rod. Philadelphia 
 pattern, 2 meters to 3.7 meters . . 14.OO 
 
 No. 151. Metric Level Rod. N. Y. pattern, 
 2 meters to 3. 7 meters .... 14.OO 
 
 No. 151 a. Rod Level for plumbing rod 3.OO 
 
 Ranging Poles 
 Painted red and white alternately 
 each foot. 
 
 No. 152. Range Pole. Solid steel octagon, 
 
 6 ft., * inch dia 3.OO 
 
 No. 153. Range Pole, iron tube round, 
 
 6 ft., 1 inch dia 2.75 
 
 No. 154. Range Pole of wood, 8 ft., steel 
 shoe 2.25 
 
 No. 155. Range Pole, like No. 1.54 but 1 O ft. 
 2.50 
 
 : , 
 i 
 
 fc..-;fe 
 
 Nos. 152 153 
 
 154 
 
Paine's Steel Tape Measures. 
 
 & inch wide. In Leather Cases, with flush handles. 
 
 So. 160. 100 feet Paine's Steel Tape, divided in lOths, .... $11.00 
 
 u 161. 50 " u " " 600 
 
 " 162. 100 " " " l > on one side, on the other 
 
 in centimeters, ... c ...... 15.00 
 
 Chesterman's Steel Tape Measures. 
 
 % inch wide. In Leather Boxes. 
 
 No. 163. 100 feet Chesterman's Steel Tape, divided in lOths, . 
 tk 164. 66 u tk " " u 
 
 u 165. 50 u u u u u 
 
 * 166. 33 " " ' ; u " . 
 
 $11.00 
 
 8.00 
 
 . 6.00 
 
 5.00 
 
 Pocket Steel Tape Measures. 
 
 In German Silver Cases, with spring and stop. 
 
 No. 167. 3 feet long, divided in lOths 80 
 
 " 168. 5 kk " " *' . 1.10 
 
 ** 169 5 "" 4k u u on one side, and in centimeters and mil- 
 limeters on the other side, 1-25 
 
239 
 
 Steel Tape Measures. 
 
 i/ 2 inch wide. Patent Brass Frame with Handle. 
 
 No. 170. 100 feet Steel Tape, divided in lOths, . 
 171. 50 " 
 
 Steel Tape Measures. 
 
 inch wide. In Leather Boxes. 
 
 No. 172. 100 feet Steel Tape, divided in lOths, 
 " 173. 66 " " " " 
 
 " 174. 50 " 
 
 liufkin Steel Tape Measures, 
 
 % inch wide. In leather case. 
 
 $11.50 
 6.60 
 
 $11.50 
 8.00 
 6.50 
 
 206. D. 
 
 203. D. ^^^^^ 103. D. 
 
 No. 206. D. 100 feet Lufkin Steel Tape, divided in lOths, . 
 No. 203. D. 50 " " " " 
 
 No. 103. D. 50 " " " " " " | inch 
 
 inchdia.; 5 oz. in weight; can be carried in vest pocket . 
 
 wide; 
 
 $11.00 
 6.00 
 
 4.00 
 
240 
 
 Surveyors' Chain Tapes. 
 
 Heavy J^-inch Steel Tapes. 
 
 Graduations etched on bright raised surfaces. 
 Graduated to single feet, end feet to tenths (one side only). 
 
 No. 175. 
 
 No. 17oa. 100 feet, complete with reel 
 " 175b. 200 " " " 
 
 " 175c. 500 " " " " 
 
 $7.50 
 10.50 
 21.50 
 
 No. 176. 
 
 No. 176a. 100 feet, complete with reel 
 " 176b. 200 " " " 
 
 ' 4 176c. 6QP " * " . 
 
 $7.50 
 10.60 
 21.50 
 
241 
 
 Lucas's Improved Steel Tapes. 
 
 % incli wide. 
 
 All tapes of this manufacture are made from the best quality of clock-spring steel, 
 one-fourth of an inch wide, and of thickness best adapted to strength and flexibility, 
 tempered straight, and graduated under tension, being drawn on steel bars made to 
 correspond with U.S. standard, and are guaranteed to be as accurate as any tapes made 
 
 in this country. The graduations are made each 
 five feet or links, according to the style of tape, 
 by brass or german silver bands firmly soldered 
 to the tape, and marked each side with plain 
 figures in such a manner as to be conveniently 
 read from either end without liability of error 
 in count. The intermediate points of feet or 
 links are marked by a small brass rivet through 
 the tape, with raised head on each side so as to 
 be easily seen. Each end foot on Engineers' 
 tapes is graduated to tenths of a foot. The ad- 
 justments for taking measure are so arranged 
 that no difference is made by the use of large 
 or small marking pins, the measurement being made and taken from the same side of 
 the pin. Soldering of the number bands secures them from peeling up or rusting 
 underneath. The method of numbering avoids the necessity of changing ends of 
 tape, it works same with either end forward. 
 
 No. 178 D. 100 feet, Engineer's, graduated to feet, each five feet by soldered 
 
 bands marked with figures, end leet to tenths of a foot $4 00 
 
 No. 178 K. 66 feet, Surveyor's, graduated to links, with figured bands every five 
 
 links 3.50 
 
 Metal Reel, $2. 00 extra. Ring handles included in price of tape. 
 Tension and Temperature sent with each tape when sold 
 
 Roe's Steel Tapes on Brass Reel. 
 
 \i inch wide. 
 
 These tapes are made of superior steel, 
 % inch wide, graduated every foot by a 
 brass rivet, end feet in tenths. Every five 
 feet has a brass plate with the numbers, 
 and every ten feet has a copper plate 
 with numbers. 
 
 They are graduated from a standard 
 tape certified to by an official of the 
 U. S. Coast Survey Department as cor- 
 rect at a temperature of 62 F. 
 
 No. 179 1 A. 100 feet long, graduated every foot, end feet in tenths, . $5.00 
 7A. 50 " " " " " " " " " . 4.00 
 
 Prices above include a Patent Brass Reel and pair of Patent Brass Detachable 
 Handles. 
 
 Brass Reel, without Tape, SI. 50 
 
 Detachable Handles, per pair, 0.30 
 
 Tape Repairer 
 
 No. 179 P. 
 
 Tape Repairer 
 1000 Eyelets 
 Complete Outfi; 
 
 $2.75 
 
 1.25 
 (postage 17 cents extra) 4.00 
 
 NOTE. This repairer cuts a clean hole one-sixteenth of an inch in diameter through two thicknesses 
 of the ordinary engineer's tapes, such as Lufkin's, Chesterman's, etc. No filing is required except to round 
 the rough corners of the break. Place the tape on the rubber pad and punch the hole in the required place. 
 Next place an eyelet on the pivot provided for it, insert it in the hole and rivet it. The first rivet holds the 
 tape in position for cutting and riveting the rest. Repairs ran. be made quickly, without any danger of split- 
 ting the tape, thus avoiding any chance of dirt collecting under the splices, of cutting the fingers when draw- 
 ing the tape through the hands, or catching in rags, etc., when cleaning. 
 
2-12 
 
 Standard Steel Tape Measures. 
 
 For city and bridge engineering, in lengthg from 100 to 1000 feet. 
 
 No. 180. 
 
 These tapes are of exact United States Standard and have no joints. They are 
 *$enerally made in lengths of 300 feet with graduations at every 10 feet, the last 1C 
 feet graduated in single feet, and the last foot into lOths. For railroad and under- 
 ground work we frequently furnish them in lengths of 400 and 500 feet. A clamping 
 handle can be furnished to attach to the tape at any desired length, if shorter 
 measures than the whole length are intended to be made. We also can furnish a 
 small brass clamp to fasten on the tape in order to mark lengths that are used re- 
 peatedly. 
 Price of tape 100 feet, graduated at every 10 feet, the last 10 feet graduated 
 
 in single feet, the last foot in lOths, 
 
 Price of tape 200 feet, graduated as above, 
 
 " " " 300 " " " " 
 
 " " " 400 " " . " 
 
 " " " 500 " M ... 
 
 66.30 
 9.45 
 12.60 
 15.75 
 18.90 
 
 Extras to Standard Steel Tape Measures. 
 
 Each additional graduation and figuring. 
 Reel, handle and stop to wind up tape, 
 2 large brass handles to unship, 
 Clamping handles, each, 
 Small brass clamp to fasten on tape, 
 
 $0.20 
 
 3.50 
 
 2.50 
 
 1.50 
 
 .75 
 
 So. 191 
 
 44 192 
 " 193 
 e * 194 
 
 Metric Steel and Metallic Tape Measures. 
 
 In Leather Boxes. 
 
 20 Meter Steel Tape, divided in meters and centimeters, 9mm. wide $11.00 
 10 " ki " fck u 9 " 600 
 
 20 ' 4 Metallic Tape, divided in meters and centimeters, 17 mm. wide 3.50 
 10 " Metallic Tape, divided in meters and centimeters, 17 mm. wide 2.75 
 
Jtfo. 195. Surveyors' Chain, 2 poles, 50 links, No. 12 best steel wire, brazed 
 
 links and rings, $5.50 
 
 " 196. Surveyors' Cham, 4 poles, 100 links, No. 12 best steel wire, brazed 
 
 links and rings, 9.00 
 
 " 197. Engineers' Chain, 50 feet, 50 links, No. 12 best steel wire, brazed 
 
 links and rings, 6.00 
 
 " 198. Engineers' Chain, 100 feet, 100 links, No. 12 best steel wire, brazed 
 
 links and rings, 10.00 
 
 Metric Chains. 
 
 No. 199. 20 Meter Chain, 100 links,No. 12 best steel wire, brazed links and rings, 10.00 
 " 200. 10 " " 50 ^ " " " " " 5.50 
 
 Extras to Tapes and Chains. 
 
 No. 201. Pocket Thermometer, $1.50 
 
 " 202. Spring Balance and Level, 5.00 
 
 No. 203. Set of Marking Pins, eleven in a set, steel wire, No. 6, . . $1.50 
 
 Odometer. 
 
 No. 204. An instrument for measuring distances traveled by carriage, . $15.00 
 
 Pedometer. 
 
 No. 205. An instrument for measuring distances walked, in german silver 
 
 case, of the size of a watch, $5.00 
 
244 
 
 C. L. BKRGEK & SONS. 
 
 Lamp for Illuminating: Cross Wires* 
 
 No. 209. Lamp for illuminating cross wires through the axis of the 
 telescope when mounted at the side, for use in underground 
 work, of brass and nickel-plated, with ground lens, . $7.00 
 
 * 210. Small Plummet Lamp, O f brass, steel point, 16 oz., . 8.00 
 44 211. Large Plummet Lamp, of brass, steel point, 24 oz., . 10.00 
 Box with shoulder straps, for pair of Plummet Lamps, 8.00 
 
 No. 210. 
 
 Plummet Lamp. 
 
 tfo. 212. 
 
 No. 214. No. 
 
 Plumb Bobs of Precision. 
 
 No. 212. Plumb Bob of Brass, steel point, shape as in cut, 8 oz., $1.75 
 
 213. " " " " " No. 212, 11 oz., 200 
 
 214. " " " " "incut, 6 oz., . . . 1.75 
 
 215. " " " " " No. 214, 9 oz., a 200 
 
 216. " " " patent reel adjustment, 8 oz., . . . 1.75 
 
 217. " " " " " " 12 oz., 2.25 
 
 218. " " with steel shank passing through the body for shaft work, 3 lb., . &00 
 
 219. " " " " " " 41b., . 7.50 
 
 220. Mercury Plumb Bob (body of steel) 12 oz., 5% inches long % inch diameter . . 2.25 
 
 ' " " I6oz.,6 " 1 " " 2.75 
 
245 
 
 Pocket Magnifiers. 
 
 No. 221 
 
 No. 224. 
 
 No. 221. Zylonite Case, as in cut, size of lens 1 inch diameter, . . . |o.60 
 
 " 222. " " " 221, k ' " IX ... .90 
 
 " 223. " " l ' 221, " " iy 2 > ... 1.15 
 
 " 224. " " u cut u of lenses, \% and 1% in diameter, . 1.30 
 
 Gossamer, Craveiiette and Silk Bags. 
 
 No. 225. Gossamer or Waterproof Bag, to cover Level in case of rain or dust, 
 " 226. Silk Bag, to cover Transit with solid silver graduations 
 '* 226a. Cravenette Bag to cover Transit, ..... 
 
 Lubricants. 
 
 No. 227. Bottle of Fine Watch Oil, for lubricating Transit Centers, etc. . 
 
 Utensils for Cleaning Instruments. 
 
 No. 228. Camel's Hair Brush 
 
 " 229. Stiff Brush for cleaning screw-threads 
 
 u 230. Chamois-skin for cleaning lenses, centers, etc. . 
 
 " 231. Stick for cleaning centers 
 
 $1.00 
 1.00 
 1.00 
 
 .$0.40 
 .40 
 .50 
 .30 
 
 Spirit Levels. 
 
 No. 232. Engineers' Spirit Levels of all sizes and grades of ensitiveness, accu- 
 rately ground and tested by us. 
 Per inch, according to length and diameter .... 
 
 from $0*80 to $1.00 
 
 Surveyor's Umbrella 
 
 Large, well-made umbrella designed as a protection 
 from sun's rays and wind, during field work. Staff pro- 
 vided with a side socket and shoe. Umbrella has rings 
 to which guy lines may be attached. 
 
 Code word, Tycuin 
 
 Price $6.OO 
 
246 
 
 Portable Anemometers. 
 
 These instruments are extensively used in 
 studying and controlling the ventilation of 
 dwellings, public buildings, factories, mines, 
 etc. 
 
 The velocity of the air current is measured 
 by means of a very light fan wheel, whose 
 revolutions are recorded on a dial. 
 
 This fan wheel is very delicate, the vanes 
 being made of aluminum, and the axis of hard 
 steel runs in j^wel bearings. 
 
 The counting mechanism is enclosed in a 
 dust-pro~f case, and can readily be thrown 
 into or out of action by a disconnecting lever. 
 
 The instrument is provided with a thumb- 
 sere w for attaching it to a rod for use in meas- 
 uring the velocity of air currents at any point 
 on the surface of the earth, mine shafts, in 
 pipes, conduits or narrow channels. In this 
 case the c -anting mechanism is thrown in or 
 out of gear by pulling on cords of different 
 colors. 
 
 This A nemometer is carefully rated and sup- 
 
 plied WITH A CORRECTION NUMBER. 
 
 Anemometer, Counting up to 10,000, OOP 
 ft. ; diameter of fan, Gin. ; complete, packed in 
 polished wooden box, $3O.OO. 
 
 The Brunton Patent Pocket Mine Transit. 
 
 A pocket instrument which takes the place of a sighting compass, clinometer, pris- 
 matic compass, and an Abney level or Locke's level. Weight 8 ounces. Price, $2O.OO 
 
 Brunton Mine Transit with leather sling case, . . . 22.25 
 
247 
 
 NEW PARTS FOR OUR TRANSITS ANI> LEVELS LIABLE TO LOSS 
 
 OR ACCIDENT. 
 
 The following list of parts of our Transits and Levels can be supplied in emergency cases 
 when it is impossible to send us the instrument. (Articles not given in this list cannot be fur- 
 nished unless the instrument is sent. ) 
 
 NOTE- As we make many styles and sizes of instruments, a mere description in your letter of 
 what is wanted may not be sufficient. For this reason to prevent mistakes and loss of time we 
 always require the serial number and size of the instrument, and a rough sketch 
 when the list below and the names given in the cross-section cut on pages 29 and GO do not 
 indicate the parts wanted. Sending the broken pieces will also help to identify the part and the 
 size. 
 
 We cannot undertake to work by sketch or measures, and only agree to send the parts men- 
 tioned in this list to fit as near as possible without having the instrument. (If we are to do the 
 fitting to detached parts sent to us there will be an extra charge made for such final fitting in 
 addition to the price given in the list below.) 
 
 Parts marked thus(*) can be sent to fit approximately only. In all cases where single 
 parts sent out such as a leveling or a tangent screw fits too tightly or too loosely a competent 
 instrument maker should make the final fitting, and it is only when too far removed from one 
 that a good local optician, jeweller or watch maker should do it. If there is no one to make the 
 final fitting in the town or vicinity, send us with the order the parts, such as the bracket for 
 which the new tangent screw is required, or the leveling head for leveling screws, or level mount- 
 ing tubes, frames for glass shades, etc., for proper fitting. 
 
 Under no circumstances ever detach a standard, center, horizontal circle, verniers, or level arms, 
 etc., from the instrument. 
 
 Before ordering an article from the list below, please read Notes A. B. C. etc., 
 page 249. 
 
 When applying any personal treatment to parts requiring care, it will be well to first read the 
 various chapters on ' Care of our instruments," etc., on pages 10 to 22 of our Manual, 
 which is sent out with each instrument purchased also the various notes appended to this list. 
 
 Emery must never be used in any form under any circumstances for fitting as this 
 would spoil the part treated. 
 
 Parts sent to us by mail should be REGISTERED to ensure delivery. 
 
 The prices below do not include registration. Add 1C cents if registra- 
 tion is desired. 
 
 In order to avoid opening accounts for small amounts, the price, including postage, (and 
 registration if any ) should accompany the order. 
 
 NEW PARTS FOR TRANSITS 
 
 SL/B/FPT Tn For illustration see page 29. 
 
 WITHOUT IVOT/CE 
 
 Hood: (Cravenette is supplied for Transits, unless silk is specified) . 
 
 Price Postage Code 
 $1.00 .04 Acerb 
 
 (New box cannot be supplied without having the instrument.) 
 
 Plumb bobs, see page 244. For Transits No. 1 and 5 use No. 213 2.00 .12 Ache 
 
 2,3,4,6 212. . 1.75 .09 Achor 
 
 Plumb bob adjuster. ......... .15 .01 Acute 
 
 Pocket magnifying glasses, see page 245. For all styles and sizes of 
 
 Transit except No. 4 use No. 222 ... .90 .02 Adore 
 
 For No. 4 use No. 221 . . . .60 .02 Aigre 
 
 Set of rubber cushion* (4) for outside bottom of mahogany box .30 .02 Alcor 
 
 Adjusting pins .......... .08 .01 Alpia 
 
 Instrument packing piece (brass ring to screw instrument upon the slide 
 
 board) 1.00 .10 Amber 
 
 Tripod: 
 
 (For entire tripods see page 158O.) 
 
 Tripod head (See Note B ) for instruments having four leveling screws 
 ' " complete with bolts, nuts and washers 
 
 bolt @$.90) . 
 
 nut . . . . . . @ .35 [ see Note C 
 
 washer 1. 2. 3. . . . .05) 
 
 cap of aluminum .... 
 
 leg full length, split, 
 " extension (See Note D) 
 
 shoe 1. 2. 3. 
 
 V clamp for extension leg (See Note C ) 
 
 1.50 
 3.00 
 4.25 
 .35 
 1.00 
 
 .35 
 .50 
 .04 
 .02 
 .01 
 .10 
 Ex 
 Ex 
 .06 
 .07 
 
 Babel 
 
 Dacca 
 
 Badge 
 
 Bafta* 
 
 Balmy 
 
 Banco 
 
 Bandy 
 
 Basis 
 
 Baton 
 
 Bavin 
 
PRICES SUBJECT TO CHANGE 
 WITHOUT NOTICE 
 
 Leveling: Head: 
 
 248 
 
 'Leveling screw with ball and socket cup attached (See Note A) 
 
 Cup only for leveling screw ......... 
 Foot-plate on which instrument is mounted. 
 Spiral Spring for tangent motion ..... 
 Spring bolt or plunger 
 
 @ 1.80 
 @ .25 
 4.50 
 .20 
 25 
 
 .04 
 .01 
 .30 
 .01 
 .01 
 
 Capal 
 Caddy 
 Cairn 
 Calid 
 Canal 
 
 Screw cap at end of spring box case ...... 
 Hook and chain for plumb bob suspension* 
 
 !25 
 .10 
 
 '.01 
 
 Caper 
 Calmy 
 
 Horizontal Circle and Vernier Plate: 
 
 
 
 
 Clamp screw ......... 
 
 1.20 
 
 .02 
 
 Dace 
 
 *Tangent screw (see Note A )...... 
 
 1.00 
 
 .02 
 
 Dais 
 
 * Vernier glass, of piano-parallel crystal glass. (See Note E) . 
 Ground glass shade for vernier . . . " " . 
 
 1.00 
 .60 
 
 .03 
 031 
 
 Dater 
 Delve 
 
 Shade frame for ground glass shade (See Note E) 
 
 1.20 
 
 .02 
 
 Divan 
 
 Spiral spring ......... 
 Spring bolt or plunger . ...... 
 
 Screw cap to hold spring in case ...... 
 
 .20 
 .25 
 .25 
 
 .01 
 .01 
 .01 
 
 Depth 
 Digit 
 Ditch 
 
 Compass: 
 
 
 
 
 Needle, (See Note F) and pivot (must be fitted to the instrument) 
 
 5.00 
 
 
 Domal 
 
 Pivot 
 
 .50 
 
 
 Donzcl 
 
 Glass cover, (piano-parallel crystal glass) ...... 
 
 1.00 
 
 .14 
 
 Kldain 
 
 Telescope's- Cross Axis: 
 
 
 
 
 Clamp screw (See Note G ) . 
 
 1.00 
 
 .03 
 
 Fadge 
 
 
 .20 
 
 .01 
 
 Fagot 
 
 Spring bolt .... 
 
 .25 
 
 01 
 
 *- "f**** 
 Fancy 
 
 Screw cap for spring case ......... 
 
 .25 
 
 .01 
 
 Feint 
 
 Acorns (protecting ends of cross axis ) . 
 
 @ .50 
 
 .02 
 
 Felon 
 
 Vertical Circle: 
 
 Screws for guard. 
 
 .25 .01 Gnarl 
 
 Telescope: 
 
 (We cannot supply new object glasses and eye-pieces without 
 having the instrument, or at least the telescope. See Note H. ) 
 Cross and stadia -wires (see Note I. ) 
 Cap for object glass for sizes No. 1 and 2 Transit, (11" to H" dia.) 
 
 No. 4 Transit . (1J* and less dia) . 
 " eye-piece erecting ....... 
 
 inverting ....... 
 
 Sunshade, for transits of our regular size and kinds give diameter 
 where it is to fit 
 
 1.00 
 
 .80 
 
 1.20 
 
 1.00 
 
 .02 
 .02 
 .02 
 .02 
 
 Haifv 
 liaise 
 Harsh 
 Helix 
 
 .75 and 1.00 .04 Hoist 
 
 Spirit Levels: 
 
 Plate level, finely ground and graduated ...... $1.50 .05 Ibex 
 
 Mounted in its tube when latter is sent us including registration . 1.95 Ichor 
 
 Standard level finely ground and graduated ..... 1.50 .05 Ideal 
 
 Mounted in its tube when latter is sent us including registration . 1.95 Ides 
 
 Telescope level finely ground and graduated ..... 3.50 .05 Image 
 
 Mounted in its tube when latter is sent us including registration . 4.00 Imban 
 
 Adjusting nut ........... .20 .01 Incog 
 
 NEW PARTS FOR WYE AND DUMPY LEVELS 
 
 For illustration see page 6O. 
 
 For prices of other parts not given here see above list of New Parts for Transits. 
 
 Hood of gossamer rubber, give length of telescope over all 
 Stirrup locking pin . . 
 
 Center nut at bottom of spindle ..... 
 Spirit level, finely ground and graduated, $4.50 
 
 Mounted in its tube when latter is sent us. 5.00 
 
 1.00 
 .70 
 .35 
 
 .05 
 .01 
 .01 
 .25f 
 
 Jadea 
 Jamb 
 Javel 
 Jetty 
 
249 
 
 NOTES TO THE PRECEDING LIST OF ARTICLES 
 SUPPLIED BY MAIL. 
 
 A. Concerning Tangent and Leveling- Screws. 
 
 Tangent and leveling screws can only be made to fit as nearly as possible without having the instrument in our 
 shop. Both kinds are micrometer screws, made with great care and fitted to the particular instrument, and, therefore, 
 are not interchangeable. When possible the tangent piece or bracket, or in the case of a leveling screw the whole 
 leveling head should be sent us, so that we can fit it properly. 
 
 If for instance the tangent screw sent you in the absence of the tangent piece or bracket should fit too 
 tightly and you have nobody to fit it, then if you can wait, unscrew the tangent piece and send it to us by regis- 
 tered mail. Make sure to replace each small screw into its screw hole in the plate. If the screws are transposed 
 they may project through, touching the circle and injuring it. 
 
 If you have an instrument repairer in your vicinity, he can fit the screw by working it in and out in its nut 
 with a little tallow until it works freely, then in the temperate or frigid zone the tallow must be removed from the 
 screw and female thread by using a little benzine on a rag wrapped around a stick. When free from -tallow a little 
 watch oil or vaseline should be applied as a lubricant. A jeweler or optician should be able to do this. 
 
 Under no circumstances should, aay emery be used on one of these screws, as this would spoil it for 
 ever. If nat successful the entire tangent piece and the screw should be sent us by registered mail, as already 
 mentioned. 
 
 A-:VOTKIK. Tripod head. 
 
 When a new tripod head is required for an instrument having four leveling screws on account of its being 
 bent, or the screw threads worn too loose, then generally a new lower foot-plate to leveling head (see list above) 
 and a new packing piece to screw instrument to the slide board in box will be needed also. 
 
 I 
 
 49-NOTEC. Tripod bolts, nuts, washers, clamps and shoes. 
 
 Send us an outline sketch on paper obtained by running a sharp pointed pencil closely around the article 
 desired. 
 
 3-NOTJ2 . Tripod legs. 
 
 As the extension tripod legs and clamps vary in size and have been changed in style from those formerly sup- 
 plied, it will be necessary to denote the size by sending the outline obtained as in Note C. 
 
 *-;VOTKK. Glass shades, vernier glasses and shade frame. 
 
 Send the broken pieces or an outline sketch as described in Note C. If the vernier glasses, etc., sent are too large 
 a local optician may grind them to size. If too loose the frame should be narrowed at the top. 
 
 49-NOTEF. Magnetic needle. 
 
 When a new needle seems to be required on account of loss of magnetism, the trouble is usually that the point 
 of the pivot is dull and then needs to be carefully sharpened to a fine point or that the Jewel 
 cap may have It -come rougn or rusty and needs to be polished .%. very little magnetism is 
 required to make the needle work satisfactorily when the pivot point is sharp and the cap well polished. 
 To preserve the sharpness of the pivot It Is necessary to use great care In lowering the 
 needle onto the center point, since it may be dulled the first time it is used if the needle is 
 dropped carelessly upon its pivot. 
 
 49-rvoTE G. Clamp screws to the telescope's axis. 
 
 Only an ordinary regular telescope clamp screw can be supplied. All transits provided with a striding level 
 or a solar attachment require a clamp screw especially made with head of smaller diameter to enable the passage 
 of these features around the head of the clamp screw when the telescope is revolved on its horizontal axis. A 
 sketch with the size and length of head is to accompany the order. 
 
 49-NOTEH. Object glass and Eye-piece. 
 
 Sometimes it happens that an object glass is slightly warped by the excessive heat of summer, shown by a 
 distortion of the image, making it impossible to obtain a sharp, well Defined image, or that the extreme cold of 
 winter may crack the balsam (see description of the telescope page 31 N with which the lenses are cemented to- 
 gether, shown by numerous streaks or stars. (A few such streaks or stars are not hurtful, since they cut out 
 only a very small amount of light.) Such an object glass should be sent to us for recementing. Then, in most 
 cases, a new cell is also needed in which to mount it again which adds to the cost of repairing. 
 
 In every permissib'e case the entire telescope should be sent us. After the object glass or telescope is returned 
 to the sender it it neeesiary to readjust the cross wires for coiiimatlon as explained under "Ad- 
 justments" on page 54 of catalog. 
 
 49-NOTEi. Stadia wires. 
 
 Stadia wires must be fitted specially to the focal length of each object glass, and therefore, we should receive 
 the entire te.lescope If possible, or at least ihe object glaan, and it will also b well to atato 
 whether the telescope is erect or inverting, a* otherwise w can only furnish the wires ap- 
 proximately correct. 
 
 When a new object glass is required, now stadia wires as a rule must be supplied also. 
 
250 
 
 J Tripod Head 
 
 2 // Bolt 
 
 3 * .* Nut 
 
 4 // // Waster 
 
 5 * Leg * 
 
 FootPlate 
 
 7 Bal/andSocketJoint 
 
 8 Lew/ing Head 
 
 9 
 /O // 
 
 11 Shi ft ing Plate 
 
 12 Plumb BobSuspending cup 
 
 13 * * Chain and Hook 
 
 14 Repeating Center 
 
 15 Clamp Collar 
 
 16 Lover Clamp. 
 
 17 H * Thumbscrew 
 
 18 u Tangent6cretf 
 
 19 // Spring,riotShc/w/i 
 
 20 * // PistorMfotshonff> 
 
 21 // * Cap. Not Shown 
 
 22 Inner center -79 
 
 23 Horizontal Circle 
 
 24 Vernier Plate C/amp 80 
 
 25 i> <Scretf 
 
 26 Vernier Plate 
 
 27 * * Tanaent Brae feet 
 
 28 
 
 29 * * Spring 
 
 30 Tange/itSpringP/ston 
 
 31 * cap 
 
 32 Horizontal Vernier 
 
 33 VemierCorer&ass 
 
 34 * Shade frame 
 
 35 ,. Glass 
 
 36 Compass CorerGtass 
 
 37 tfeedle 
 
 38 * P/wt 
 
 39 Lifter 
 
 40 A // Screw Head 
 
 41 Front Plate Lewi 
 
 42 , * V/ff/ 
 
 43 * n * MjustingMfc 
 
 44 // // >/ Rocker 
 
 51 Side Le&l Rocker 
 
 52 rial 
 
 53 Telescope fa/s 
 $4 i Barrel 
 55 Fye p/ece Mounting 
 
 46 JJaJustable M/e Bearing 
 
 47 CapandScretxs 
 
 49 Adjusting Screw 
 
 50 * Fastening jcrev 
 
 57 Terrestr/a/ Eye Piece 
 
 58 t/ePieceCap 
 
 , * ffing 
 
 63 * Head 
 
 64 u u Sere* 
 
 65 u H <Sadd/e 
 
 66 u u u Screws 
 
 67 fbject Slide 
 
 68 // Head 
 
 69 n Glass cell 
 
 70 H Glass 
 
 72 JunSnade 
 
 73 Te/escope Clamp 
 
 74 tt * 
 
 75 mster 
 
 77 Yert/caltirc/e 
 
 78 
 
 79 u 
 
 80 tertical termer 
 8/ / * Screw 
 
 Cross section of the Berger Transit. 
 
1 . L. BEKGEK & SONS. 
 
 INDEX 
 
 PAGE 
 
 Abney Level and Clinometer 119 
 
 Adjustable Center for Mine Transits 202 
 
 Plumb-Bob 7, 52, 244 
 
 Adjustments of Auxiliary Side and Top Tel- 
 escope 93-97 
 
 " Axis of Revolution with 
 
 Striding Level 57 
 
 " Cross Wires 22, 54-55, 58, 93-97 
 
 " Dumpy Levels 63 
 
 " Instruments 20-27 
 
 " Level to Telescope . 55, 59, 62-64 
 " Line of Collimation .... 58 
 " Striding Level, Resting on 
 
 Special Collars 56 
 
 " Striding Level, Improved, 
 
 Resting on Special Collars 57 
 " Striding Level, Resting at 
 
 Points of Contact in Wyes 57 
 " Telescope Standards .... 54 
 
 " Transits 53 
 
 " Vertical Arc or Circle ... 55 
 
 " Wye Levels 62 
 
 Alt-Azimuths 222-224 
 
 Aluminum for Instruments of Precision .... 23 
 
 Anemometer, Portable 246 
 
 Arc, Beaman Stadia 155, 197 
 
 " Movable 196 
 
 " Pennsylvania 196 
 
 Arc or Vertical Circle, Adjustment of 55 
 
 Different Types 155, 196-200 
 
 Arm with Magnifier, Flexible 202 
 
 Artificial Horizon 228 
 
 Astronomical Transits 222-227 
 
 Auxiliary Telescope, Style 1, Interchangeable 
 
 Top and Side 93-97, 189-190, 192-195 
 
 Bags, Gossamer and Silk 245 
 
 Beaman Stadia Arc 155, 197 
 
 Berger Solar Attachment 172 
 
 Adjustment and Use 
 
 of 65-92 
 
 Bevel Limb Transit 253 
 
 Bracket for Underground Use 203 
 
 Brunton Pocket Mine Transit 246 
 
 Brushes 245 
 
 Care of Centers and Graduations 11 
 
 " " Instruments 10-20 
 
 " " Telescope Lenses 12 
 
 Catalog and Price-List 103-253 
 
 Center, The Adjustable, for Centering under a 
 
 given point 202 
 
 Centers 43 
 
 Care of 11 
 
 Shifting, for Transits 52 
 
 Steel 126, 130, 132, 134, 212 
 
 Centering Arrangement for Transit over a 
 
 given point 52 
 
 Chains, Engineers' and Surveyors' 243 
 
 Chesterman Tapes 238 
 
 Circles, Reflecting 228 
 
 Vertical 56, 155, 199-200 
 
 Circles and Verniers, Graduation of ... 37-42 
 
 City Transits 150-169,212-221 
 
 Clinometer 119 
 
 Collimation, Line of 22 
 
 Compass, Surveyors' Transit 7, 43 
 
 Marine 235 
 
 Miners' 235 
 
 Needle 98-99 
 
 Oblong 212 
 
 Pocket 235. 246 
 
 PAGE 
 
 Compass, Prismatic 235 
 
 Surveyors' 235 
 
 Vernier Pocket 235 
 
 Construction of Instruments . . 8 
 
 Cross-Level, Revolving 201 
 
 Cross Section of Spirit Levels 26 
 
 " Transit 29, 250 
 
 " Transit Telescopes 30 
 
 " " Wye Level 60 
 
 " " Wye Level Telescopes ... 61 
 
 Cross Wires 16, 22, 51, 54, 56, 93-96 
 
 Adjustment of . . 22, 54-55, 58, 93-97 
 
 Illumination of 8, 220 
 
 Replacement of Broken 16 
 
 Current Meters 230-232 
 
 Davis' Solar Attachment 174-175 
 
 Adjustment and Use 81 
 
 Declination, Reduction 67-68, 80 
 
 Observation 83-84 
 
 Diaphragms, Different Styles of Wire .... 122 
 
 Disappearing Stadia Wires 190 
 
 Distance Measurements by Stadia Wires . . 6, 88-92 
 Double Opposite Vernier Attachment .... 155 
 
 Dumpy Levels, Engineers' 123-129 
 
 Adjustment of 63 
 
 Dust Guard, Collapsible 128 
 
 Edge Graduation for Vertical Circle . . 198-199 
 
 Excelsior Tapes 239 
 
 Eye Piece, Diagonal 175 
 
 Pancratic 34 
 
 Face Graduation for Vertical Circle . . 199-200 
 
 Finish, Styles of 9 
 
 Gradienter Screw 6, 45 
 
 Tables 48-51 
 
 Graduations 5, 34-42 
 
 Care of 10 
 
 Hand Levels 119 
 
 Hoods, Gossamer and Silk 245 
 
 Horizon, Artificial 228 
 
 Hydrographers' Wye Level 136-137 
 
 Illumination of Cross Wires 8, 220 
 
 Improved Prism and Colored Glass Attach- 
 ment 174-175 
 
 Inclined Square 174 
 
 Instruments, Adjustment of ... 20, 27-67, 93-97 
 
 Care of 10-22 
 
 " General Construction of .... 8 
 
 Repairs to 25 
 
 Transportation of 18 
 
 Interchangeable Top and Side Auxiliary 
 
 Telescope, Style I 93-97, 189-195 
 
 Lamp Targets 209 
 
 Lamps, Mining, Engineering and Plummet . . . 244 
 
 Lateral Adjuster 205-207 
 
 Latitude Level Attachment . 68, 85, 171-173 
 Observation, Portable Instruments for 226 
 
 Leather Finish 9 
 
 Lenses, Care of 12-13 
 
 Short Focus 100-101, 190, 203 
 
 Level Triers 117 
 
 Levels, Abney 119 
 
 Coast Survey Precise 144 
 
 Dumpy 123-129 
 
 Adjustment 63-64 
 
 Engineers' Precise 139-141 
 
 Wye 130-135 
 
 Adjustment 59-62 
 
 Geodetic 142-143 
 
 Hydrographers' 136-137 
 
 Latitude . 172 173 
 
C. !L. BERGER & SONS. 
 
 252 
 
 PAGE 
 . 119 
 138-155 
 , . 201 
 . 237 
 . 118 
 119 
 
 Levels, Locke's Hand 
 
 Reversion 
 
 Revolving Cross-Level . . . 
 
 Rods . . 
 
 Spirit 
 
 On Metal Base .... 
 
 Stride 201 
 
 Leveling Attachment, Quick 8, 45, 118 
 
 Rods 236-237 
 
 Screws 44 
 
 Line of Collimation 22 
 
 Locke's Hand Level 119 
 
 Lubricants 14, 245 
 
 Lucas' Steel Tapes 241 
 
 Lufkin's Steel Tapes 239 
 
 Magnifier, Flexible Jointed Arm with 202 
 
 Magnifier and Reflector 198 
 
 Magnifiers 245 
 
 Magnetic Needles, Balancing of 7 
 
 Variation of 7, 43, 44 
 
 Magnetometer 229 
 
 Magnifying Glasses 245 
 
 Marine Compass 235 
 
 Marking Pins 243 
 
 Measurements by Fixed Stadia Wires . . 88-92 
 
 Meridian, From Equal Altitudes 68 
 
 From Polaris 78 
 
 Inclination 70 
 
 Tables 77 
 
 Observation for 71 
 
 Meters, Current 230-232 
 
 Metric Chains 243 
 
 Steel and Metallic Tapes 242 
 
 Miners' Compass 235 
 
 " Lamps 244 
 
 Mining Transits 182-209 
 
 Mirror with Universal Joint . . . 127, 137, 140-141 
 
 Mountain Transits 176-183 
 
 Movable Arc 196 
 
 Object Glasses, Abnormally Large 33 
 
 Object-Slide, Protection to 8 
 
 Oblong Compass 147, 160, 212 
 
 Odometer 243 
 
 Offsetting Arrangement 8, 53 
 
 Optical Adjustment of Instruments 27 
 
 " Principles of Engineers' Telescope ... 27 
 
 Packing of Instruments 9, 18 
 
 Paine's Tapes 238 
 
 Pancratic Eye Piece 34 
 
 Pantograph, Precision 233 
 
 Parts of Instruments 104, 247-249 
 
 Pedometer 243 
 
 Pendulum Apparatus 229 
 
 Pennsylvania Arc 196 
 
 Pins, Marking 243 
 
 Plain Transits 151, 168 
 
 Plane Table 146-147 
 
 Planimeters, Compensation 233 
 
 Rolling Ball 234 
 
 Suspended Ball 234 
 
 Plumb-Bobs 7, 244 
 
 Plumbing and Centering Arrangement 52 
 
 14 Device for Carrying a Line Down a 
 
 Shaft 188, 191 
 
 Plummet Lamp 244 
 
 Pocket Compass 235 
 
 Magnifiers 245 
 
 Sextant 229 
 
 Tapes 238, 242 
 
 Polaris, To Find Meridian from 78 
 
 Poles, Ranging 237 
 
 Portable Anemometer 246 
 
 Astronomical Instruments. . . 225-227 
 
 Time Transit 225-227 
 
 Precise Level, Coast Survey 144 
 
 Engineers' 139-141 
 
 Price List 103 
 
 Prism and Colored Glass Attachment . 174-175 
 
 Prismatic Compass 235 
 
 Protection of Instruments . 14 
 
 PAGE 
 
 Protection of Object Slide 8 
 
 Quick Leveling Attachment 8, 45, 118 
 
 Railroad Transits 150-169 
 
 Ranging Poles 237 
 
 Reading Glass and Reflector 198 
 
 " with Flexible Arm 202 
 
 Glasses 245 
 
 Reconnoissance Transits 182-183 
 
 Reflecting Circle 228 
 
 Repair of Instruments 25 
 
 Repairer, Tape 241 
 
 Replacing Wires' 16 
 
 Reversion Levels 138, 155 
 
 Road Builders' Dumpy Level 123 
 
 Rods, Leveling 236-237 
 
 Roe's Tapes 241 
 
 Rolling Ball Planlmeter 234 
 
 Setting up Transits 53 
 
 Sextants 229 
 
 Shifting Center for Transits with Three Level- 
 ing Screws 52 
 
 Shifting Tripod 7 
 
 Short Focus Lens 100-101, 190, 203 
 
 Side Telescope, Style 1 Interchangeable Top 
 
 and Side 93-97, 189-195 
 
 Sizes, Weights and Particulars of Instru- 
 ments 115 
 
 Solar Attachments 65-87. 170-174 
 
 Adjustment and Use of . 65-87 
 Coefficients of Refraction 
 
 Table 76 
 
 Davis' .... 81-87, 174-175 
 Degree of Precision Re- 
 quired for 70 
 
 Direction and Use of Davis' 
 
 81-87 
 " Form of Dally Declination 
 
 Table 67 
 
 " General Remarks Concern- 
 
 Ing Use of .... 69, 81, 87 
 Hourly Motion of Sun's 
 
 Declination 80 
 
 Inclination of Meridian . . 70 
 Inclination and Converg- 
 
 ency of Meridian, Table 77 
 Mean Refraction Tables 73-75 
 Reducing Observation . 84-87 
 Reduction of Declination 
 
 and Refraction .... 67 
 To Correct Watch .... 86 
 To Find the Latitude by the 
 
 Sun 68, 85 
 
 To Find Meridian .... 68 
 To Find Meridian from 
 
 Polaris 78 
 
 To Find Meridian from 
 
 Equal Altitude .... 79 
 Use of Nautical Almanac . 83 
 
 Solar Telescopes 97 
 
 Spider Lines of Various Diaphragms . 16, 51, 122 
 
 Spirit Levels 6, 26, 44, 118, 245 
 
 Care of 15 
 
 " " Mounting 15 
 
 " On Metal Base . . . . 119 
 
 Spring Balance and Level 243 
 
 Square, Inclined 174 
 
 Stadia Arc, Beaman 155, 197 
 
 Lines 6, 51 
 
 " Disappearing 190 
 
 Measurements 6, 88-92 
 
 Wires 6, 51, 88, 92 
 
 Standard Steel Tapes 242 
 
 Steel Tapes 238-242 
 
 " Centers, Instruments . 126, 130, 132, 134, 212 
 
 Stride Levels 
 
 142, 147, 156-159, 185, 201, 209, 213-222 
 Striding Level, Use and Adjustment .... 56-57 
 
 Suspended Ball Planimeter 234 
 
 Suspended Pantograph 233 
 
 Tachymeters ... 156-159 
 
C. L,. BERGER & SONS. 
 
 253 
 
 PAGE 
 
 Tangent Screws 7 
 
 Tape Repairer 241 
 
 Tapes, Steel and Metallic in Feet and Metric . 238-242 
 
 Chesterman 238 
 
 Lucas 241 
 
 Lufkin 239 
 
 Paine 238 
 
 Roe 241 
 
 Standard Steel 242 
 
 Telescopes, Auxiliary Top and Side, Inter- 
 changeable, Style 1 95-97, 189-195 
 
 Description of 5, 27-31 
 
 Erecting and Inverting 32 
 
 Side, Adjustments of 93 
 
 Solar , 97 
 
 Spider-line Diaphragms ... 51, 122 
 
 Top, Adjustable 95 
 
 Theodolites 212-219 
 
 Time Observation 86 
 
 " Transit 225-226 
 
 Transits, Adjustments of 27, 53-59, 93-97 
 
 Astronomical 222-227 
 
 City 150-169 
 
 Cross Section of 29-30, 250 
 
 Directions and Use of 53 
 
 Engineers' and Surveyors' . . 150-169 
 
 General Construction of 28 
 
 Mining 182-209, 246 
 
 Mountain 176-183 
 
 Plain 151, 168 
 
 Pocket, Bmnton Mine 246 
 
 Railroad 150-169 
 
 Reconnoissance 182-183 
 
 PAGE 
 
 Transits, Setting Up 53 
 
 Small, No. 2, No. 4J^, No. 4 . . 168-186 
 Solar Attachments for . 65-80, 172-175 
 
 Surveyors' 150-169 
 
 Theodolite 184-185, 210-220 
 
 Time 225-226 
 
 Triangulation 212-220 
 
 Tunnel 210-216 
 
 Wet Mine 194-195 
 
 With Level Attachment to Telescope 152 
 
 Transportation of Instruments 18 
 
 Transverse Striding Level 57 
 
 Tripods 7, 120-121 
 
 Tripods, Extension, See Note 120, 176 
 
 Half Length 120, 188 
 
 Split Leg 120, 188 
 
 Tunnel 207 
 
 Trivets 204 
 
 Tunnel Transits 210-216 
 
 Tripod 207 
 
 Umbrellas, Surveyors' 245 
 
 Variation Plate 7, 43-44, 98-99 
 
 Vernier Attachment, Double Opposite . 155, 214 
 
 Verniers 37-41 
 
 Vertical Circles, Adjustments 55 
 
 Beaman Stadia Arc for . . 155, 197 
 Edge Graduation .... 198-199 
 Face Graduation .... 199-200 
 
 Watch, Correcting by Sun 86 
 
 Weights and Sizes of Instruments 115 
 
 Wye Levels 59-62, 130-137 
 
 Adjustment of 62 
 
 Engineers' Hydrographers . . 136 
 
C. Li. Berger & Sons' Bevel-Limb Transit. 
 
 The above cut represents our Bevel Transit as made by us to order since 1871. 
 
 NOTE. While a bevel-limb graduation of a horizontal circle can be somewhat more readily seen than one on a horizontal 
 surface, it is well to remember, before ordering instruments to be made so, that there are very serious objections to their 
 general adoption for engineers' field-instruments. As will be seen in the annexed cuts, the sharper and therefore more 
 delicate edges of the soft solid silver, necessitated by the bevel at the junction of limb and verniers, are much more liable 
 to injury and wear in field use than the common horizontal graduation, where the same edges are carried down nearly rect- 
 angularly below the graduated surface. Thus, while a bevel possesses some advantages when ne-u and well constructed, 
 it soon becomes impaired by slight dents and the edges rounded by brush or finger when dust and oxyd must be removed 
 at certain times. It then can be read only with difficulty and becomes a source of great annoyance, particularly as the eye 
 looks squarely at it, thus defeating the very object sought and rendering the instrument almost unfit for good work, although 
 otherwise in good condition. We say this with an experience of twenty-five years to back up. To make it plain we must 
 have recourse to the diagrams. Fig. c is the cross-section of a horizontal limb and vernier as commonly made. It is obvious 
 that the fine silver edges at the junction of limb and verniers are in this form better protected from wear, and also that, 
 when slightly rounded by wear, or when the graduated surfaces are not in the same plane, the eye, being stationed at an 
 angle of about 45 to the limb, requiring an observer to glance along the graduated lines, will more readily see and esti- 
 mate differences in the reading of limb and verniers, thereby enabling him to obtain closer results, as verified by 
 the superior results in triangulation obtained with horizontal graduations over bevel ones formerly in vogue. Fig. a is a 
 cross-section of a bevel limb, showing the sharper edges of the graduated surfaces. When new and properly made the edges 
 of limb and verniers appear the same as those in Fig. c and a c, but when worn off they will leave a big circular space between 
 them, making the reading of an angle all the more difficult and uncertain. There are other reasons, against their general adop- 
 tion, such as that the standards for the telescope have in bevel instruments not the stability so important in angle-measuring 
 instruments unless they are mounted on a special horizontal base provided for them, (instead of on the bevel surface of the 
 upper plate) which means a great increase in weight, or that the distance between them be quite short, resulting in a shortening 
 of transverse axis of the telescope, as in the cut above, thereby increasing the instability of the same, particularly if the tele- 
 scope is of modern power and length, besides reducing the size of compass, length of plate levels, and with this the degree 
 of sensitiveness of the latter. In both these instances the standards are apt to change their distance apart affecting 
 the adjustment of the line of collimation for near distances. The greater expense of repairing, in case of accident, is also 
 an item that should be considered. It is often double or triple that of a horizontal graduation. To our mind bevel gradu- 
 ation should be confined to exceptional cases and to the larger instruments read by micrometer microscopes. 
 
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THIS BOOK IS DUE ON THE LAST DATE 
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 THIS BOOK ON THE DATE DUE. THE PENALTY 
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 Engineering- 
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 UNIVERSITY OF CALIFORNIA LIBRARY