| bee ate AN Gngineers end Curvayors | a % INSTRUMENTS, > 2 Fo eae premiere: i | | | : fe a ees es rrOvOv—o ae ALES ——+. ia a Sie Saks pe Not tN flaMALare , who LESPS Ale em A “~ « EAT RBAS 4% Ere fe k (FER 9S” - S LAX xX THE LIBRARIES COLUMBIA UNIVERSITY AVERY LIBRARY A MANUAL OF THE PRINCIPAL USED IN American Engineering and Surveying, MANUFACTURED BY Wiecé oy Eb. GURLEY. REVISED EDITION. 2 Eo TRO YS NG Ae: PUBLISHED BY W. & L. E. GURLEY. 1856. . Entered according to Act of Congress, in the year 1855, 7 he | BY W. &L. E GURLEY, In the Clerk’s Office of the District Court for the Northern Dit New York. % ; * “ + >> D. H. Jones & oo Poivrans, Troy, ING We PRICK LIST ee i TS insirumenis \ ' i : vine] ) no Sh COMPASSES. Plain, with Jacob Staff mountings, 4 inch needle, Acasa ation iced oe $20,00 zs a Opti ae Want tede amapta tie sags 25,00 he sf us ne 3 6 BY ESS ctopticcos seadog 28,00 ‘Vernier, cS we se Guess SOR LS a aieinin ste chee 50 35,00 Rail Road, “ € f 5} “ clo aus oundelau ene 55,00 EXTRAS. Compass DB RIDO WIC OUETEN LAP G rc watt oerS s/is to oyctenteaegiia's baie aa a 932 5,00 “« with lev’g screws and Clamp and Tang’t movem't, 12,00 “ce “é “c ““e +6 without & “ce 6 “6 10, 00 REMI POT UPA cea c5 ys i's Pelle wc ow delta Se os ate wns ele oe 4,00 TRANSITS. Vernier, plain telescope * 6 inch needle, with compass tripod,.... 60,00 Sur veyors’ : 5 54 “ if ACI USHUC TUM acm O0SO0 Engineers’ “ " light, 4 inch needle, a “tote? aves eae O00 “<é “6 ““ heavy, pt ** se “6 “ see 125,00 s ‘“« - with watch+telescope,.......... 150,00 “e ss Cee theodoliteraxishan acts cele 150,00 $6 os “~ two telescopes,........+-. 190,00 EXTRAS, Vertical circle, 34 in, diameter, vernier reading to five minutes, 5,00 6< 4“ 44 “e “a “ce “ec single 66 10,00 Clamp and Tangent movement to axis of telescope,...........-. 5,00 Level on Telescope, with ground bubble and scale,...........-. 10,00 Rack and pinion movement to eye glass... 1... ee eee ce wees 5,00 Sights on telescope with folding joints,.......-....ccsseescecee 5,00 cs “ Standards at right angles to telescope,............. ea LOGO) *A “plain” telescope is ene without any of the attachments, as the elamp and tangent, vertical circle and level. wo PRICE LIST. LEVELING INSTRUMENTS. Sixteen inch telescope, with adjusting tripod,. . Sane rae . $96,00 Eighteen “ BET tia) ae Seay eS” © Ria +s vil gts bee - 90,00 Twenty ‘ & 08 a es + bau eee eee sean ee 0,00 Twenty-two a a ce e6 Soe MP sco to 90,00 Farm level, ce fc us ff). Bah sen .. 40,00 Builders’ level, “ a is EA a Me ey wees 0100 LEVELING RODS Yankee. (Or BOstOnss.2., oss. 0'us 01s e wis 5. ave, 01.6 » oye ocsi0.e, 0 Ae ee 12,00 New York, with improved mountings,.............. eri I RUU CHAIN 100 feet, with oval rings, No. 5 wire, 6th Bor aewnre eo Ane 7.50 i ai eh Ke ae Ok te Se! nee oat tse aan ss 6,00 50 “* xe a se OE ae EOS ec. Cir. apres seecane 4,00 ee ae a Hy CO RR ee eR Ain 4 A ets em 3,50 6G)“ SP TOUI C Micswl MERC Ol! Micki esc ette bre «0 ae a fer 3,00 SO hee Me - 4 a i ir Peer A os se 1,76 6m td eCmmestOcl AVIRA ah nts vctne wire Clee vic oa tee big 5,00 338 CS Pg we ra ss he’) lek tis cinch Grane ’ +: wie eae 2,75 Set 10 marking Pins,.. ROTC. RO ONE nh Ne 2 5 ae 16 MEASURING TAPES. Chestermanis. steel, "88 feet... sctaceies aele Satele > efeea ae eee 7,50 ae < BOM Saget eres .ere bie (aa late og Mere. aiele eee eee 11,50 oe > OF nena te clos he AA on on . 14,50 SS 1. OV) apc) atts Bes Siena ptals..< tovatelas A's tps cmceiaiele nomena 20.00 CCL MVOEATIO ME BS Si5 (ok praise leis one bps ss 1s eheuk, ee oe ee 7 2.50 ee s DOV ois a occarepo its ot Rivet ates anim PG. 0 Sic 3,00 % fe CO ateereletere tere tere A At Ris are 3,25 Ay ss (Soe OME Wey ts a eee Cire scr ine orate PPROIE oto 3 3,50 Ke fe NO oak aio. ot ccs fees wee see ter tas aet rae eae aug ae oe Be CaS os 8 SU ele mic che la/stlelic. eens orapie 06 + wie eres eee 4,00 4 ce UOUN My SaRiae 5 oh ole 56 Biphe ue eerete Sueusae 5,00 POCKET COMPASSES. With folding sights, 24 inch needle, very serviceable for retracing “ce ce ce 6e «“c ce Without sights, 73 s “e at “ 1 to 2 lines once surveyed,......... 6,00 is with jacob staff mountings,.. 7,50 ‘“ “ ‘ “ “ 9,00 ee « without ss ¢: 8,00 $6 cs bch dhe ae eee oe from 25 ets. to 2,50 6,00 Miners’ Compasses, for tracing iron ore,.. aes ss ale + «nate For prices of Drawing Instruments, separate or in cases, refer to the Supplement to our Manual. ° eer {Information to Purchasers. Instruments Wantep.—In regard to the best kind of instruments for particular purposes, we would here say, that where only common survey- ing, or the bearing of lines in the surveys for county maps is required, a Plain Compass is all that is necessary. In cases where the variation of the needle is to be allowed, as in running over the lines of an old farm, or the surveys of Government lands, the Vernier Compass, or the Vernier Transit, is required, Where, in addition to the variation of the needle, horizontal angles are to be taken, in cases of local attraction, the Rail Road Compass is prefer- able; and for a mixed practice of surveying and engineering, we consider the Surveyors’ Transit superior to any other instrument made by us or any other manufacturers. Where Engineering is the exclusive design, the Engineers’ Transit and the Leveling Instruments are of course indispensable. The Farm and Builders’ Levels, are intended for laying out mill seats and determining the levels of buildings in course of erection. Warranty.—All our instruments are examined and tested by us in per- son, and are sent to the purchaser adjusted and ready for immediate use. They are warranted correct in all their parts—we agreeing in the event of any defect appearing after reasonable use, to repair or replace with a new and perfect instrument, promptly and at our own cost, express charges included, or we will refund the money and the express charges paid by him. Packine, &c.—Each instrument is packed in a well finished mahogany case, furnished with lock and key and brass hooks, the larger ones having besides these a leather strap for convenience in carrying. Each case is provided with screw-drivers, adjusting pin, and wrench for centre pin, and if accompanied by a tripod, with a brass plumb-bob; with all instru- ments for taking angles, without the needle, a reading microscope is also furnished. Ay INFORMATION TO PURCHASERS. Unless the purchaser is already supplied, each instrument is accompa- nied with our ‘‘ Manual,” giving full instructions for such adjustments and repairs as are possible, to one not provided with the facilities of an instru- ment maker. When sent to the purchaser, the mahogany Gases are carefully inclosed in outside packing boxes, of pine, made a little larger on all sides to allow the introduction of elastie material, and so effectually are our instruments protected by these precautions, that of several thousand sent out by us during the last twelve years, in all seasons, by every mode of transporta- tion, and to all parts of the Union, and the Canadas, not more than three or four have sustained serious injury. Means or Transportation.—Instruments can be sent by Express to almost every town in the United States and Canadas, regular agents being located at all the more important points, by whom they are forwarded to smaller places by stage. The charges of transportation from Troy to the purchaser are in all cases to be born by him, we guaranteeing the safe arrival of our instruments to the extent of express transportation, and holding the express Companies responsible to us for all losses or damages on the way. Terms or Payment are uniformly cash, and we have but one price, Our prices for instruments are nearly one-third less than those of other makers of established reputation. They are as low as we think instru- ments of equal quality can be made, and will not be varied from the list given on the previous pages. Remittances may be made by a draft payable to our order at Troy, Albany, New York, Boston, or Philadelphia, which can be procured from Banks or Bankers in almost all of the larger villages. These may be sent by mail with the order for the instrument, and if lost or stolen en the route, can be replaced by a duplicate draft obtained as before, and without additional cost. Or the customer may pay the bill on receipt of the instrument to the express agent, taking care to send funds bankable in New York or Boston. All persons ordering instruments by mail, or by proxy, may rely on receiving as perfect and cheaply as if ordered in person. W. & L. E. GURLEY, Mathematical Instrument Makers, Futon Sr., opposite Unton R. R. Depot, Troy, N. Y, ERRATUM. On page 11, six lines from bottom, in directions for ‘e-magnetizing the needle, for “ corresponding,” read o yp posite poles of the ms monet. PREFACE. In offering this little work to the public, the publishers have designed to supply a want which an experience of many years in the manufacture of Instruments, as well as practice in the field, has taught them, is very generally felt by American Surveyors and Engineers. The various Instruments employed in English and European practice are so different from those preferréd by the great majority of American Engineers, that no description of the former, however excellent, is applica- ble to such as are manufactured and used in our own country. The entire absence of any treatise upon American Instruments, as well as the numerous inquiries which are made by our business correspondents, has led us to believe that a Manual, furnishing a full deseription of the peculiarities and adjustments of those manufactured at our establishment, would be acceptable, not only to our own customers, but to the. profession generally. With the hope, therefore, that our little book may enable the Engineer and Surveyor to understand their Instruments, and discover and rectify any derangement in their adjustments, or injury from ordinary accidents, we now commit it to the indulgence of those for whom it has been _ designed. W. & L, E. GURLEY. Troy, May 1, 1856. ™ SURVEYING INSTRUMENTS. THe various instruments used in Surveying may be conve- niently arranged, into two general divisions. (1.) Neeptx instruments,—or such as owe their accuracy aud value to the magnetic needle only, embracing the Plain and Ver- nier Compasses, and ihe Vernier Transit. (2.) ANGULAR instruments, including those in which the hor zontal angles, are measured by a divided circle and verniers, a well as by-the needle also; as the Rail Road Compass, the Su veyor’s and Engineer’s Transits, &c. In the present work we shall consider first, those imstruments comprised in the first division, and; as in these the accuracy of the horizontal angles indicated, depends upon the delicacy of the needle, and the constancy with which it assumes a certain direc tion, termed the “magnetic meridian,” we shall here remarl briefly upon, the form, the dength, and the movement of the mag. netic needle, : The forms of the needle are almost infinitely varied according to the taste or fancy of the maker or surveyor, but may be re- solved into two general classes, one having the greatest breadth in a horizontal, the other-in a vertical direction. We have usually made our needles about one twentieth of an inch broad and one third as thick, parallel from end to end, the north and south poles being distinguished from each other, by a small scollop on the north end. The length of the needle varies in different instruments, from four to six or even seven inches, those of five and a half, or six inches long, being generally preferred by surveyors. 1* 6 SURVEYING INSTRUMENTS. The movement of the needle, with the least possible friction, is secured by suspending it, by a jewelled centre upon a hardened steel pivot, the point of which is made perfectly sharp and smooth. - The test of the delicacy of a magnetic needle is the number of horizontal vibrations, which it will make in a certain are, before coming to rest—besides this, most surveyors prefer also to see a sort of quivering motion in a vertical direction. This quality which is manifested more in a horizontal, than in a vertical needle and depends upon the near coincidence of the point of suspension, with the centre of gravity of the needle, serves to show merely, that the cap below is unobstructed. Having now considered the different qualities of a good needle, we shall proceed to speak of those instruments of which it makes so important a part; of these the most simple is that termed the PLAIN COMPASS. Fig. 1. i Raa LTT (OTA Ts ri ET Too enim 4 — —— i As represented above, the Plain Compass, has, a needle six JL ke tents e 8 hy THE PLAIN COMPASS. 7 inches long, a graduated circle, main plate, levels, and sights, and is placed upon the brass head of the ‘Jacob staff.” Tur Compass Crrcre, in this, as in all our instruments, is di- vided to half degrees on its upper surface, the whole degree marks being also cut down on the inside circumference, and is fig- ured from 0 to 90, on each side of the centre or “line of zeros.” The circle and face of the compass are silvered. Tue Sprrit Levens are placed at right angles to each other so as to level the plate in all directions, and are balanced, upon a pivot in the middle of the tube so as to be adjustable by a com- mon screw-driver. Tue Siaurs, or standards, have fine slits cut through nearly their whole length, terminated at intervals by large circular aper- tures, through which the object sighted upon is more readily found. Sometimes a fine horse-hair or wire is substituted for one half the slote, and placed alternately with it on opposite sights. Tancent Scare.—The right and left hand edges of the sights of our compasses, have respectively an eye-piece, and a series of divisions, by which angles of elevation and depression, for a range of about twenty degrees each way, can be taken with considera- ble accuracy. Such an arrangement is very properly termed a “ tangent scale,” the divided edges of the north sight, being tangents to seoments of circles having their centres at the eye-pieces, and their points of contact with the tangent lines at the zero divisions of the scale. The cut shows the eye-piece and divisions for angles of de- pression ; those for angles of elevation, concealed in this cut, are seen in that of the Railroad Compass. Tue Jacos Starr mountings which are furnished with all our compasses, and packed in the same case, consist of the brass head already mentioned, and an iron ferule or shoe pointed with steel so as to be set firmly in the grouud. & THE PLAIN COMPASS. The staff to which the mountings should be well fitted and driven on is procured from any wheelright, or selected by the sur- veyor himself, from a sapling of the forest. To Adjust the Compass. Tue Levers. — First bring the bubbles into the centre, by the pressure of the hand on different parts of the plate, and then turn the compass half way around; should the bubbles run to the end of the tubes it would indicate that those ends were the highest; lower them by tightening the screws immedi- ately under, and loosening those under_the lowest end until by estimation the error is half removed; level the plate again, and repeat the first operation, until the bubbles will remain in the centre, during an entire revolution of the compass. Tue Sigurs may next be tested by observing, through the shits, a fine hair or thread made exactly vertical by a plumb. Should the hair appear on one side of the slit the sight must be adjusted by filmg off its under surface on that side which seemed’ the highest. THe NEEDLE is adjusted in the following manner :—Haying the eye nearly in the same plane with the graduated rim of the com- pass circle, with a small splinter of wood, or a slender iron wire, bring one end of the needle in line with any prominent division of the circle, as the zero, or ninety degree mark, and notice if the other end corresponds with the degree on the opposite side ; if it does, the needle is said to “cut” opposite degrees; if not, bend the centre-pin by applying a small brass wrench, furnished with our compasses, about one-eighth of an inch below the point of the pin, until the ends of the needle are brought into line with the opposite degrees. Then holding the needle in the same position, turn the com- pass half way around, and note whether it now cuts opposite de- THE PLAIN COMPASS. 9 grees. If not, correct half the error, by bending the needle, and the remainder by bending the centre-pin. The operation should be repeated until perfect reversion is se- cured in this first position. This being obtained, it may be tried on another quarter of the , circle ; if any error is there manifested, the correction must be made in the centre-pin only, the needle being already straighten- ed by the previous operation. When again made to cut, it should be tried on the other quar: ters of the circle, and corrections made in the same manner until the error is entirely removed, and the needle will reverse in every point of the divided surface. To use the Compass. In using the Compass the Surveyor should keep the south end towards his person, and read the bearings from the north end of the needle. He will observe that the EE and W letters on the face of the compass are reversed from their natural position, in order that the direction of the line of sight may be correctly read. The compass circle being graduated to half degrees, a little practice will enable the surveyor to read the bearings to quar- ters, or even finer—estimating with his eye the space bisected by the point of the needle, and as this is as low as the Traverse ta- ble is usually calculated, it is the general practice. Sometimes, however, a small vernier is placed upon the south end of the needle, and reads the circle to five minutes of a de- gree—the circle being in that case graduated to whole degrees. This contrivance, however, is quite objectionable on account of the additional weight imposed on the centre-pin, and the diffi- culty of reading a vernier which is in constant vibration, and is therefore but little used. To Taxes AnaLes or Exevation.—Having first leveled the compass, bring the south end towards you, and place the eye at 10 THE PLAIN COMPASS. the little button, or eye-piece, on the right side of the south sight, and with the hand fix a card on the front surface of the north sight, so that its top edge will be at right-angles to the divided edge, and coincide with the zero mark; then sighting over the top of the card, note upon a flag-staff the height cut by the lme of sight; then move the staff up the elevation, and carry the ecard along the sight until the line of sight again cuts the same height on the staff, read off the degrees and half degrees passed over by the card, and we shall have the angle required. For ANGLES oF Depression.—Proceed in the same manner, using the eye-piece and divisions on the opposite sides of the sights, and reading from the top of the standards. The compass is furnished with a ball spindle, or socket, upon which it turns, and by which it is leveled. The ball may be placed in a single or ‘jacob staff” socket, as represented in the figure, or in a compass tripod, such as is shown im the cut of the Vernier Transit beyond. In the side of the hollow cylinder, or socket, of the compass which fits to the ball spindle, is a screw by which the instru- ment may be clamped to the spindle in any position. Besides the clamp screw, we have recently fitted to the sockets of our compasses a little spring catch, which, as soon as the in- strument is set upon the spindle, shps into a groove and thus re- moves all danger of falling when the instrument is carfied. There is also underneath the mam plate a needle-lifting screw, which, by moving a concealed spring, raises the needle from the pivot, and thus prevents the blunting of the point im transpor- tation. When the compass is not in use it is the practice of many Surveyors to let down the needle upon the point of the centre- pin, and let it assume its position in the magnetic meridian so as to retain or even increase its polarity. We would advise in addition, that after the needle has settled \ THE PLAIN COMPASS. tt it should be raised against the glass, in order not to dull the point of suspension. A little caution is necessary in handling the compass, that the glass covering be not excited by the friction of cloth, silk, or the hand, so as to attract the needle to its under surface. A brass cover is sometimes fitted over the glass as a precau- tion against disturbances of this kind. When, however, the glass becomes electric, the fluid may be removed by breathing upon it, or touching different points of its surface with the moistened finger. An ignorance of this apparently trifling matter has caused many errors and perplexities in the practice of the inexperienced Surveyor. Repairs of the Compass. To enable the Surveyor to make such repairs as are possible without having recourse to an instrument maker, we here add a few simple directions. 1. Toe Nerepie.—It may sometimes happen that the needle has lost its polarity, and needs to be re-magnetized ; this is effect- ed in the following manner : The operator being provided with an ordinary permanent mag- net,* and holding it before him, should pass with a gentle pres- sure each end of the needle from centre to extremity over the magnetic pole, describing before each pass a circle of about six inches radius, to which the surface of the pole is tangent, draw- ing the needle towards him, and taking care that the north and south ends are applied to the corresponding poles of the magnet. Should the needle be returned ina path near the magnetic pole, the current induced by the contact of. the needle and mag- net in the pass above described, would be reversed, and thus the magnetic virtue almost entirely neutralized at each operation. When the needle has been passed about twenty-five times in * A magnet suitable for this purpose costs from 12 to 25 cents, 12 THE PLAIN COMPASS. succession, in the manner above described, it may be considered as fully charged. a A fine brass wire is wound .in two or three coils on the south end of the needle, and niay be moved back or forth, in order to counterpoise the varying weight of the north end. 2, Tum Centre-Pin.—This should occasionally be examined, and if much dulled, taken out with the brass wrench, already _ spoken of, or with a pair of plyers, and sharpened on a hard oil stone —the operator placing it in the end of a small stem of wood, or a pin vice, and delicately twirling it with the fingers as he moves it back and forth at an angle of about 45° to the surface of the stone. When the point is thus made so fine and sharp as to. be invisi- ble to the eye, it should be smoathed by rubbing it on the surface of a soft and clean piece of leather. 3. To pur In 4 New Guass.—Unscrew the “bezzle ring ” which holds it, take out the little brass ring and the old glass, and scrape out the putty; then if the new glass does not fit, smooth off its edges by holding it obliquely on the surface of a grind-stone, until it will enter the ring easily ; then put im new putty, spring in the brass ring, and the operation will be completed. 4, To REPLACE A Sprrit Levert.—Take out the screws which hold it on the plate, pull off the brass ends of the tube, and with a knife-blade, scrape out the plaster from the tube; then with a stick, made a little smaller than the diameter of the tube, and with its end hollowed out, so that it will bear only on the broad surface of the level vial, push out the old vial, and replace it with a new one, taking care that the crowning side, which is usually marked with a file on the end of the vial, is placed on the upper side, When the vial does not fit the tube it must be wedged up by putting under little shps of paper until it moves in snugly. After the vial is in its place, put around its end a little boiled THE PLAIN COMPASS. 13 plaster, mixed with water to the consistency of putty, taking care not to allow any to cover the little tip of the glass, then slip in the brass ends, and the operation will be completed. We would here remark that an extra glass and level vials are always furnished, free of charge, with our instruments whenever desired by the purchaser. Sizes of the Plain Compass. Three different sizes of this instrument are in common use — having respectively four, five, and six inch needles, and differing also in the length of the main plate, which in the four inch Com- pass is twelve and a half inches long, and in the larger sizes fifteen and a half inches. The six inch needle compass is generally preferred. The Plain Compass, which was the only one in use in this country previous to the time of David Rittenhouse, has grad- ually given way to the superior advantages of the Vernier or Rittenhouse Compass, which we shall now proceed to describe. 2 SURVEYING INSTRUMENTS. THE VERNIER COMPASS. Fig. 2. The Vernier Compass, represented in fig. 2, differs from the instrument just described, in having its compass circle with a vernier attached, movable about a common centre, by turning the ‘tangent screw,” seen at the south end of the plate. The superiority of the Vernier over the Plain Compass consists in its adaptation to the retracing the lines of an old survey, and in the surveys of the U.S. public lands, where the lines are based on a true meridian. THE VERNIER COMPASS. 15 Variation of the Needle. It is well known that the magnetic needle, in almost all parts of the United States, points more or less to the east or west of a true meridian; or north and south line. _ This deviation, which is called the Varration or Drciina- TION of the needle, is not constant, but increases or decreases to a very sensible amount in a series of years. Thus at Troy, N. Y., a line bearing m 1830, N. 31° E. would now, 1856, with the same needle, have a bearing of about N. 32° K., the needle having thus in that interval, traveled a full degree to the west. For this reason, therefore, in running over the lines of a farm from field notes of some years standing, the Surveyor would he obliged to make an allowance, both perplexing and uncertain, in the bearing of every line. : To avoid this difficulty the vernier was devised, the arrange- ment of which we shall now describe. Tur VERNIER is divided on its edge to thirty equal parts and figured in two series on each side of the centre. In the same plane with the vernier is an-.arc or limb, fixed to the main plate of the compass, and graduated to half degrees. The surfaces of both vernier and limb are silvered. On the vernier are thirty equal divisions, which exactly cor- respond in length with twenty-nine of the half degrees of the limb. Each division of the vernier, is therefore, one-thirtieth, or, in other words, one minute longer than a single division of the limb. To Reap THE VERNIER.—In “reading” the vernier, if it is moyed to the right, count the minutes from’its zero point to the left, and vice versa. Proceed thus until a division on the vernier is found exactly in line with another on the limb, and the lower row of figures on the vernier will give the number of minutes pas- sed over, When the vernier is moved more than fifteen minutes 16 THE VERNIER COMPASS. to either side, the number of the additional minutes up to thirty or one-half degree of the limb is given by the upper row of figures on the opposite side of the vernier. To read beyond thirty, add the minutes given by the vernier to that number, and the sum will be the correct reading. In all cases when the zero point of the vernier passes a whole degree of the limb, this must be added to the minutes, in order to define the distance over which the vernier has been moved. To TURN OFF THE V ARIATION.—It will now be seen, that the Surveyor having the Vernier Compass, can by moving the vernier to either side, and with it of course the compass circle attached, set the compass to any variation. He therefore places his instrument on some well defined line of the old survey, and turns the tangent screw until the needle of his compass indicates the same bearing as that given in the old field notes of the original survey. Then screwing up the clamp screw underneath the vernier, he can run all the other lines from the old field notes without further alteration. The reading of the vernier on the limb in such a case, would give the change of variation at the two different periods. The variation of the needle at any place being known, a true meridian, or north and south line, may be run by moving the vernier to either side, as the variation is east or west, until the are passed over on the limb is equal to the angle of variation; and then turning the compass until the needle is made to cut the zeros on the divided circle, when the line of the sights would give the direction of the true meridian of the place. Such a change in the position of the vernier is always necessary in surveying U. 8. public lands, which are always run from the true meridian. “THE LINE OF NO VARIATION,” as it is called, or that upon which the needle will indicate a true north and south direction, is situated in the United States, nearly in an imaginary line drawn THE VERNIER COMPASS. 1? from the middle of lake Erie to cape Hatteras, on the coast of North Carolina. A Compass needle, therefore, placed east of this line, would have a variation to the west, and when placed west of the line, the variation would be to the east, and in both cases the varia- tion would increase as the needle was carried farther from the line of no variation. Thus in Minnesota the variation is from 15° to 16° to the east, while in Maine it is from 17° to 18° to the west. At Troy, in the present year, 1856, the variation is about 7° 44’ to the west, and is increasing in the same ¢lirection from two to three minutes annually, To Reap to Minutrs.—A less important use of the vernier is to give a reading of the needle to single minutes, which is ob- tained as follows: First be sure, as in all observations, that the zero of the ver- nier exactly corresponds with that of the limb; then noting the number of whole degrees given by the needle, move back the compass circle with the tangent screw until the nearest whole de- eree mark is made to coincide with the point of the needle, read the vernier as before described, and this. reading, added to the whole degrees, will give the bearing to minutes. To Use the Vernier Compass. Proceed in the same manner as directed in regard to the Plain Compass, when making new surveys, always taking care that the vernier is set at zero and securely clamped by screwing up the nut beneath the plate. In surveying old farms, allowance and correction must be made for the variation, as just described. Sizes of the Vernier Compass. We make but one size of this instrument, having a six inch needle and a main plate fifteen and a half inches long. The adjustments of the Vernier Compass are mainly those of the instrument first described, and need not here be repeated. 2% , SURVEYING INSTRUMENTS. THE VERNIER TRANSIT. Fig. 3. \\ \ \ \ vn The Vernier Transit or Transit Compass, represented in the cut above, has the same general properties as the Vernier Com- pass, but is furnished with a telescope in place of the ordinary sights. i f —CO£ES Sef THE VERNIER TRANSIT. 19 The telescope is from ten to twelve inches long, and sufficiently powerful to see and set a flag at a distance of two miles, in a clear day. The cross bar in which it is fixed, turns readily in the standards, so that the telescope can be turned in either direction, and back and fore sights be taken without removing the instrument. Like all telescopes used by us in our in- struments, it shows objects in an erect po- sition. Tur TrLescopr.—The interior construc: tion of the telescope of the Vernier Transit which is very similar to those of the other instruments we shall describe, is well shown zin the longitudinal section represented in e fig. 4. As here seen, the telescope consists essen- tially of an object-glass, an eye-piece tube, and a cross-wire ring, or diaphragm. The object-glass is composed of two lens- es, one of flint, the other of crown glass, which are so made and disposed, as to show the object seen through it without color or distortion. The object-glass, and the whole Telescope is therefore said to be “achromatic.” The eye-piece is made up of four plano- convex lenses, which, beginning at the eye end, and proceeding on, are called, respect: ively, the eye, the field, the amplifying, and the object lenses. 20 THE VERNIER TRANSIT. Together, they form a compound microscope, magnifying the minute image of any object formed at the cross wires by the in- terposition of the object-glass. Fig. 5. Tur Cross Wires.—The cross-wire diaphragm, two views of which are here exhibited, is a small ring of brass, suspended in the tube of the telescope by four capstan head screws, which press upon the washers shown on the outside of the tube. The ring can thus be moved in either direction, by working the screws with an ordinary adjusting pin. Across the flat surface of the ring two fine fibres of spider’s web are extended at right angles to'each other, their ends bemg cemented with bee’s wax, or varnish, into fine lines cut in the metal of the ring. The intersection of the wires forms a very minute point, which, when they are adjusted, determines the optical axis of the tel- escope, and enables the Surveyor to fix it upon an object with the greatest precission. The imaginary line passing through the optical axis of the telescope, is termed the “line of collimation,” and the operation of bringing the intersection of the wires into the optical axis, is i dhe THE VERNIER TRANSIT. xt called the ‘adjustment of the line of collimation.” This will be hereafter described. The openings in the telescope tube are made considerably larger than the screws, so that when these are loosened, the _ whole ring can be turned around for a short distance in either direction. The object of this will be seen more plainly, when we describe the means by which the wire is made truly vertical. The sectional view of the Telescope (fig. 4,) also shows two moveable rings, one placed at A A, the other at C C, which are respectively used, to effect thé centering of the eye-piece, and the adjustment of the object-glass slide. The centering of the eye-tube is performed after the wires have been adjusted, and is effected by moving the ring, by means of the screws, shown on the outside of the tube, until the intersec- tion of the wires is brought into the centre of the field of view. The adjustment of the object slide, which will be fully described in our account of the Leveling Instrument, secures the movement of the object glass in a straight line, and thus keeps the line of collimation in adjustment through the whole range of the slide, preventing at the same time what is termed the “traveling” of the wires. This adjustment, which is peculiar to our telescopes, is always made in the process of construction, and needing no further at- tention at the hands of the Engineer, is concealed within the hol- low ball of the telescope axis. Optical Principles of the Telescope. In order that the advantages gained by the use of the tele- scope may be more fully understood, we shall here venture briefly to consider the optical principles involved in its construction. We are said to “see” objects because the rays of light which proceed from all their parts, after passing through the pupil of the eye, are by the crystalline lens and vitreous humor, converged 22 THE VERNIER TRANSIT. to a focus on the retina, where they form a very minute inverted image; an impression of which is conveyed to the brain by the optic nerve. The rays proceeding from the extremities of an object, and crossing at the optic centre of the eye, form the “visual angle,” or that under which the object is seen. The apparent magnitude of objects depends on the size of the visual angle which they subtend, and this being great or small, as the object is near or distant—the objects will appear large or small, in an inverse proportion to the distances which separate them from the observer. Fig, 6. Thus, (in fig. 6, ) if the distance O A is one- half of O B, the visual Bangle, subtended by the object at the point A, and therefore the appa- rent magnitude of the rH s= object will be twice that observed at B. If, therefore, the visual angle subtended by any object, can be made by any means twice as large, the same effect will be produced as if the observer were moved up over one-half the intervening distance. Now this is the principal advantage gained in the use of a telescope. The object-glass receiving the rays of light which proceed from all the points of a visible object, converges them to a focus at the cross wires, and there forms a minute, inverted, and very bright image, which may be seen by placing a piece of ground glass to receive it at that pot. The eye-piece acting as a compound microscope, magnifies this image, restores it to its natural position, and conveys it to the eye. The visual angle which the image there subtends, is as many times greater than that which would be formed without the use of the telescope, as the number which expresses its magnifying power. Fig. 7. THE VERNIER TRANSIT. Zo Thus, a telescope which magnifies twenty times, increases the visual angle just as: much, and therefore diminishes the apparent distance of the object twenty times—or in other words, it will show an object two hundred feet distant, with the same distinctness, as if it was distant only ten feet from the naked eye. The accompanying cut, (fig. 7,) which we are kindly permitted to copy from an excellent treatise on surveying, by Prof. Gillespie of Union College, will give a correct idea of the manner in which the rays of light coming from an object are affected, by passing through the several glasses of a telescope. ; We shall only consider the rays which proceed from the extremities ; ; these after passing through the object-glass, here shown as a single lens, are conveyed to the point B, the centre of the cross wires and the common focus of the object and eye glasses. At this place the rays crd&8s each other and the image is inverted. The rays next come to the object lens C, and passing through it are refracted so as again to cross each other, and come thus to the amplifying lens D. By this they are again refracted, made more nearly parellel and thus reach the large field lens H. After passing through this, they form a magnified and erect image in the focus of the eye lens G. By the eye lens the image is still further magnified, and at last enters the eye of the ob- server, subtending an angle as much greater than that at the point O, as is the magnifying power of the telescope. In place of the eye-piece of four lenses, which 24. THE VERNIER TRANSIT. we have just been considering, and which is exclusively used in oO) all American instruments made at the present day; another, which has but three lenses, is often seen in the telescopes of im- ported instruments. This latter, which inverts the object, hana saving a little more light than the former, is exceedingly troublesome to the in+ experienced observer, and has never been popular in American Engineering. To ascertain the Magnifying Power of a Telescope. Set up the instrument about twenty or thirty feet from the side of a white wooden house, and observe through the telescope the space covered by one of the boards in the field of the glass; then, still keeping that eye on the Telescope, hold open the other with the finger, if necessary, and look with it at the same object. By steady and and careful observation there will be seen on the surface of the magnified board, a number of smaller ones seen by the naked eye, count these and we shall obtain the magnifying power. If the limits of the magnified board, as seen through the telescope, can be noted so as to be remembered after the eye is removed, the-number of boards contained in this space may then be easily counted. The side of an unpainted brick wall, or any other surface, con- taining a number of small, well marked and equal objects, may be observed, in place of the surface we have described. The operation described requires great care and close-observa- tion, but may be performed with facility after a little practice. We have spoken of the effect of the telescope in magnifying obiestsy but have not mentioned what is termed its “ illuminating power.” This arises from the great diameter, or aperture of the object- glass, compared with that of the pupil of the eye, which enables the observer to intercept many more rays of light, and bring the object to the eye highly illuminated. THE VERNIER TRANSIT. Ao The advantage gained in this increase of light depends, as is evident, on the size of the object-glass, and the perfection with which the lenses transmit the heht without absorbing or reflect- ing it. _ The superficial magnifying power of a telescope, is found by squaring the number which expresses its linear magnifying power ; thus a telescope which magnifies twenty times, increases the sur- face of an object four hundred times. Before an observation is made with the telescope, the eye- piece should be moved in or out, until the wires appear distinct to the eye of the operator; the object-glass is then adjusted by turning the pinion head until the object is seen clear and well defined, and the wires appear as if fastened to its surface. The intersection of the wires, being the means by which the optical axis of the telescope is defined, should be brought pre- cisely upon the centre of the object to which the instrument is directed. Having thus briefly considered the principles, we will now pro- ceed to describe the - Attachments of the Telescope. A telescope is said to be “plain” when it is without any ap- pendages to its tube or axis, and most instruments are made in that manner. Many surveyors, however, prefer to add these conveniences, and we shall now consider them in detail: CLAmp AND Tancent.—This consists essentially of a ring, en- circling the axis of the telescope, and having two projecting arms, the one above being slit through the middle and holding the clamp screw, the other much longer and below, is connected with the tangent screw. As soon as the clamp screw is tightened, the ring is brought firmly around the axis, and the telescope can then be moved up or down by turning the tangent screw. The clamp and tangent ought always to accompany the vertical circle and the level on the telescope. 3 26 THE VERNIER TRANSIT. VerticaL Circte.—A divided circle, as seen in the cut of the Vernier Transit, is often attached to the axis of the telescope, giving, with a vernier, the means of measuring vertical angles, with great facility. We make two sizes of these circles, one of staat 3 1-2 inches diameter, seen with this instrument, the other an inch larger, and shown in the cut of the Engineer’s Transit. The former is gra- duated to single degrees, and reads, by the vernier, to five minutes of adegree. The latter, divided to half degrees, gives a reading, with the vernier, to single minutes. The vertical circle is fitted firmly to the telescope axis, and fastened with a screw, so that it remains permanent. The vernier however, may be shifted in either direction, by loosening the screws which confine it to the standards. The vernier of the small circle is divided into twelve equal parts, which correspond with thirteen degrees on the circle. Each division of the vernier 1s, therefore, one-twelfth of onc degree, or five minutes longer than a single division of the circle so that the angles are read to five minutes of a degree. The vernier is double, having its zero point in the middle, an — the reading up to thirty minutes, is said to be direct: that is, if th circle is moved to the right, the minutes are read off on the righ side of the vernier, and vice versa, The minutes beyond thirty are obtained on the opposite side, and in the lower row of figures, By following these directions, and noticing the first divisions on the circle and vernier, which exactly correspond, the surveyor can obtain a reading to five minutes, with great facility. LeveL ON TEeLEscope.—Besides the vertical circle, there is sometimes a small level attached to the telescope of this, and other instruments, which we shall hereafter describe. Such an attachment is shown in the cut of the Surveying Tran- sit, and its adjustment and advantages will be explained in our ac: count of that instrument. THE VERNIER TRANSIT. 27 Sieuts on TeLescore.—We are sometimes desired by survey- ors, to place a pair of short sights on the upper side of the tele- scope tube. They are best made to fold close to the tube, when not in use, sike- those of the pocket compass, described hereafter. These sights are thought to be useful in taking back sights without turning the telescope, and in sighting through bushes or in the forest. We believe, however, that a telescope is incomparably better, in every situation, and would never advise their construction or use, Sicuts ror hiaur Ancies.—Besides the sights just mentioned, we have often attached others to the plate of the instrument, on either side of the compass circle, or on the standards. These being adjusted to the telescope, give a very ready means of laying off right angles, or running out offsetts, without chang- ing the position of the instrument. To Adjust the Vernier Transit. TuE Levens of this instrument have a capstan head screw at each end, and are adjusted with a steel pin in the same manner as those of the Vernier Compass. Tur NerEDLE is adjusted as described in our account of the Plain Compass. Line or Couitimation.—To make this adjustment, which is, in other words, to brmg the intersection of the wires into the optical axis of the telescope, so that the instrument, when placed in the middle of a straight line will, by the revolution of the Telescope, cut its extremities—proceed as follows: Set the instrument firmly on the ground and level it carefully ; and then having brought the wires into the focus of the eye- piece, adjust the object glass on some well defined point, as the edge of a chimney, or other object, at a distance of from two to five hundred feet; determine if the vertical wire is plumb, by clamping the instrument firmly to the spindle and applying the 28 THE VERNIER TRANSIT. wire to the vertical edge of a building, or observing if it will “move parallel to a point taken a little to one side; should any de- viation be manifested, loosen the cross wire screws, and by the pressure of the hand on the heads outside the tube, moye the ring around until the error is corrected. The wires being thus made respectively horizontal and vertical, fix their point of intersection on the object selected; clamp the instrument to the spindle, and having revolved the telescope, find or place some good object in the opposite direction, and at about the same distance from the instrument as the first object assumed. Great care should always be taken im turning the telescope, that the position of the instrument upon the spindle is not in the slightest degree disturbed. Now, having found or placed an object which the vertical wire bisects, unclamp the imstrument, turn it half way around, and direct the telescope to the first ohject selected; having bisected this with the wires, again clamp the instrument, revolve the Tele- scope, and note if the vertical wire bisects the second object observed. Should this happen, it will indicate that the wires are in adjust- ment, and the points bisected, are with the centre of the instru- ment, in dhe same straight line. If not, however, the space which separates the wires from the second point observed, will be double the deviation of that point from a true straight line, which may be conceived as drawn through the first point and the centre of the instrument, since the error is the result of two observations, made with the wires when they are out of the optical axis of the telescope. Fig. 8. For as in the diagram, let A represent the centre of the instru- THE VERNIER TRANSIT. 29 ment, and B C the imaginary straight line, upon the extremities of which the line of collimation is to be adjusted. B represents the object first selected, and D the point which the wires bisected, when the telescope was made to revolve. When the instrument is turned half around, and the telescope again directed to B, and once more revolved, the wires will bisect an object, H, situated as far to one side of the true line as the point D is on the other side. The space, D H, is therefore the sum of two deviations of the wires from a true straight line, and the error is made very appa- rent. In order to correct it, use the two capstan head screws on the sides of the telescope, these being the ones which affect the po- sition of the vertical wire. Remember that the eye-piece inverts the position of the wires, and therefore, that in loosening one of the screws, and tightening the other on the opposite side, the operator must proceed as if to increase the error observed. Having in this manner moved back the vertical wire until, by estimation one quarter of the space, D E, has been passed over, return the instrument to the point B, revolve the telescope, and if the correction has been carefully made, the wires will now bisect a point, C, situated midway between D and j, and in the prolongation of the imaginary line, passing through the point B and the centre of the instrument. To ascertain if such is the case, turn the instrument. half around, fix the telescope upon B, clamp to the spindle, and again revolve the telescope towards ©. If the wires again bisect it, it will prove that they are in adjustment, and that the points B, A, C, all lie in the same straight line. Should the vertical wire strike to one side of C, the error must be corrected precisely as above described, until it is entirely removed. Another method of adjusting the line of collimation, often employed in situations where no good points in opposite directions 3% 30 THE VERNIER TRANSIT. can be selected upon which to reverse the wires may here be described. The operator sets up the instrument in some position which commands a long sight in the same direction, and having leveled his instrument, clamps to the spindle, and with the telescope locates three points which we will term A, B, and CG, which are distant from the instrument about one, two, and three hundred feet, respectively. These points, which are usually determined by driving a nail into a wooden stake set firmly into the ground, will all lie in the same straight line however much the wires are out of adjustment, since the position of the instrument remains unchanged during the whole operation. Having fixed these points, he now moves the instrument to B, and sets its centre directly over the nail head, by lettmg down upon it the point of a plumb-bob suspended from the tripod. Then having leveled the instrument, he directs the wires to A, clamps to the spindle, and revolves the telescope towards C. Should the wires strike the nail at that point, 1t would show that they were in adjustment. Should any deviation be observed, the operator must correct it by moving the wire with the screws until, by estimation, half the error is removed, Then bringing the telescope again upon either A or C, and revolving it, he will find that the wires will strike the point in the opposite direction, if the proper correction has been applied. If not, repeat the operation until the telescope will exactly cut the two opposite points, when the intersection of the wires will be in the optical axis, and the line of collimation in adjustment. In our description of the previous operation, we have spoken more particularly of the vertical wire, because in a revolving telescope this occupies the most important place, the horizontal one being employed mainly to define the centre of the vertical THE VERNIER TRANSIT. 31 wire, so that it may be moved either up or down without materially disturbing the line of collimation. The wires being adjusted, their intersection may now be brought into the centre of the field of view. Tur Hyr-pixce, is centred by moving the screws A A, shown in the sectional view of the telescope Fig. 4, which are slackened and tightened in pairs, the movement being now direct, until the wires are seen in their proper position, It is here proper to observe that the position of the line of collimation depends upon that of the object-glass, solely, so that the eye-piece may, as in the case just described, be moved im any direction, or even entirely removed and a new one substituted, without at all deranging the adjustment of the wires. Tue Stranparps.—In order that the wires may trace a vertical line as the telescope is moved up or down it is necessary that both the standards of the telescope should be of precisely the same height. To ascertain this and make the correction if needed, proceed as follows: : Having the line of collimation previously adjusted, set the instrument in a position where points of observation, such as the point and base of~ a lofty spire, can be selected, giving a long range in a vertical direction. Level the instrument, fix the wires on the top of the object, and clamp to the spindle; then bring the telescope down, until the wires bisect some good point, either found, or marked at the base ; turn the instrument half around, fix the wires on the lower point, clamp to the spindle, and raise the telescope to the highest object. If the wires bisect it, the vertical adjustment is effected; if they are thrown to either side, this would prove that the standard opposite that side, was the highest, the apparent error being double that actually due to this cause. 82 THE VERNIER TRANSIT. To correct it, we now make one of the bearings of the axis movable, so that by turning a screw underneath this sliding piece as wellas the screws which hold on the cap of the standard, the adjustment is made with the utmost precision, This arrangement which is common to all our telescope imstru- ments is very substantial and easily managed. Tur VERTICAL CIRCLE.— W hen this attachment requires adjust- ment proceed by leveling the instrument carefully, and having brought into line the zeros of the wheel and vernier find, or place some well defined point, or line, which is cut by the horizontal wire. Turn the instrument half around, revolve the telescope, and fixing the wire upon the same point as before, note if the zeros are again in line. If not, loosen the screws, and move the zero of the vernier over half the error; bring the zeros again into coincidence, and proceed precisely as at first described, until the error is entirely corrected, when the adjustment will be completed. Should it be desired, at any time, the circle can be removed by the surveyor, and replaced at pleasure. Tur Leven on TELescopre.—The adjustment of this will be best considered when we come to speak of the Surveyors Transit. ADJUSTMENTS IN GENERAL.—We ought here to say that the above adjustments, as well as all the others which we have previously explained or may hereafter describe, are always made by us in person, but are given in this work in order that the, Surveyor and Engineer may fully understand their instruments and be enabled to detect and remedy errors and accidents which in practice will often occur. To Use the Vernier Transit. This instrument is used on the ordinary ball and spindle placed most commonly in the compass tripod as shown in Fig, 3. THE VERNIER TRANSIT. 83 Trirop Hrap.—Sometimes leveling screws with the parallel plates, and which together we shall designate the “tripod head” with a clamp and tangent movement, are used with this instrument as well as with the Surveyors Transit. This tripod head can be unscrewed from the legs, and is packed in the instrument box ; it is of very moderate cost, and in almost every situation is infinitely superior to a_ ball and socket support. Ban AND Socker.—This we also make in all cases where the tripod head is furnished by cutting a screw upon the lower end of the jacob staff, a ball and spindle being also supplied so that the Surveyor can use the same instrument either upon a jacob staff, a compass tripod, or a leveling tripod. Compounp Bati.—We also manufacture what may be termed a “compound ball spindle,” which has a tangent movement, and gives all the perfection of more costly arrangements, with a very moderate expense. As represented in the cut, it has an inte- rior spindle, around which an outside hollow cylinder is moved, by turning the double- headed tangent screw, which has in the mid- dle, an endless screw, working into teeth, cut spirally around in a groove of the cylinder. The compass, or other instrument, revolves on the outside socket, precisely as if placed (Fig. 9.] on a common ball spindle; but when a slower movement is required, can be made fast by the clamp screw, and then turned gradually around the interior spindle, by the tangent screw, until the slote of the sight, or the intersection of the wires, is made to bisect the object with the utmost cer- tainty. ‘The compound ball may be placed either in a jacob-staff socket, or compass tripod. 84 THE VERNIER TRANSIT. Tue Spring Carcau, described in our account of the Plain Compass, is always attached to the socket of this instrument, whether placed upon a ball or tripod, so that jt cannot slip off from the spindle in carrying. THE Ciamp Screw, in the side of the secleat of this instru- ment, is shown in Fig. 3, and by pressing a brass spring in the in- terior against the spindle, serves to fix the instrument in any position, THe VeRNIER is moved by the tangent screw, now always, placed above the plate, precisely as described in our account of the Vernier Compass, and is read to minutes in the same manner, There is also a clamp nut underneath the vernier by which it is securely fixed in any position, which must be loosened whenever the vernier is moved by the tangent screw. Tur Nerpie Lirtina Screw is the same as those of the compasses previously described. In SurveYING with this instrument, the operator proceeds pre- cisely as with the Vernier Compass, keeping the south end to- wards his person, reading the bearings of lines from the north end of the needle, and using the telescope in place of sights, revolving it as objects are selected in opposite directions. Parattax.—Before an observation is made with the telescope, the eye-piece should be moved in or out until the wires appear distinct to the eye of the operator ; the object glass may then be placed in position, by turning the pinion head on the top of the telescope until the object is seen clear and well defined, and the wires appear as if fastened to its surface. When on the contrary, the wires are not perfectly visible, the observer by moving his eye to either side of the small aperture of the eye-piece will cause the wires to “travel” on the object, and thus occasion what is termed the “error of parallax.” The intersection of the wires being the means by which the optical axis of the telescopes is defined, should be brought pre- cisely upon the centre of the object to which the mstrument is directed. THE VERNIER TRANSIT. 85 To Take ANGLES or ELevation.—Level the instrument care- fully, fix the zeros of the circle and vernier in line, and note the height cut upon the staff or other object by the horizontal wire ; then carry the staff up the elevation, fix the wire again upon the same point, and the angle of elevation will be read off by the vernier. By careful usage, the adjustments of the vernier transit will remain as permanent as those of the ordinary compass, the only one liable to derangement, being that of the line of collimation. This should be examined occasionally, and corrected in the manner previously described. Repairs of the Vernier Transit. These being in great part already spoken of, it will be neces- sary to consider only such as belong to the telescope. To RepLace THE Cross Wires.—Take out the eye-piece tube, together with the little rmg by which it is centered, and having removed two opposite cross wire screws, with the others turn the ring until one of the screw holes is brought into view; in this thrust a stout splinter of wood or a small wire, so as to hold the ring while the other screws are withdrawn ; the ring is then taken out and is ready for the wires. For these the web of the spider is to be preferred above any thing else, but when this is not obtainable a fine silk fibre may be substituted. We usually procure our webs from the living manufacturer directly, selecting those of a yellowish-brown color as furnishing the most perfect. product. The spider being held between the thumb and fingers of an as- sistant in such a posifion as to suffer no serious injury, and at the same time be unable to make any effectual resistance with his ex- tremities, the little fibre may be drawn out at pleasure, and being placed in the fine limes cut on the surface of the diaphragm, is then firmly cemented to its place by applying softened beeswax with the point of a knife blade. 36 THE VERNIER TRANSIT. In case the spider is not procurable, a fine strand of a web- which is free from dust and long enough to serve for both wires, may be selected. In such times as the spiders remain in their winter quarters, we have been able to procure very good fibres froma box in which a number had bgen confined. ‘ When the wires are cemented, the ring is returned to its posi- tion in the tube, and either pair of screws being inserted, the splinter or wire is removed and the ring turned until the other screws can be replaced. Care must also be taken that the same side of the ring is turned to the eye-piece as before it was removed. When this has been done, the eye tube is inserted and its center- ing ring brought into such a position that the screws im it can be replaced, and then by screwing on the end of the telescope, the little cover into which the eye tube is screwed, the operation will be completed. To CLeaAn tHe TreLescopr.—The only glasses that will ordi- narily require cleaning are the object glass on its outside surface, and the little eye lens, which is exposed when the cap of the eye tube is removed. To remove the dust from these use a very soft and clean silk or cotton cloth, and be careful not to rubythe same part of the cloth a second time on the surface of the glass. No one should ever be allowed to touch the glasses with the fingers or with a dusty cloth. Excellencies of the Vernier Transit. These are due chiefly to the telescope and its attachments, and from what has been already said, it will appear are such as to ren- der this instrument greatly superior to one provided with the or- dinary sights. 1. The magnifying power of the telescope enables the surveyor to take accurate observations at distances entirely beyond the reach of the naked eye. NEEDLE INSTRUMENTS. id 2. The fine intersection of the cross wires can be set precisely upon the centre of the object. 3. The revolving property of the telescope gives the means of running long lines up or down steep ascents or descents with per- fect ease, where, with the short sights of the ordinary compass, two or three observations would have to be taken. 4, The use of a telescope entirely avoids the incessant trying of the eyes, experienced in surveys with the ordinary sights. 5. With the telescope, lines can be run through the forest or brushwood, and the flagstaff distinguished with much greater cer- tainty than with the sights of a compass. This statement may appear very unreasonable to those not fami- liar with the instrument, and these in fact, raise the greatest ob- jection toa telescope, from its supposed unfitness for surveys in such locations. They have only to use it a few times in this kind of work, in connection with a flagstaff, painted white or covered with paper, to distinguish it from the surrounding objects, to be convinced of its great superiority. In the Vernier Transit, as furnished by us, is supplied, as we believe to the surveyor, the most perfect of all needle intruments, and this at a cost but little above that charged by other makers for a sight compass. The advantages of the telescope and its attachments are so great, that a surveyor, accustomed to them, would find it difficult to content himself with the ordinary compass, and such in fact is the universal testimony of those familiar with the Vernier Transit. GENERAL REMARKS. We have now described the instruments included under the division termed Needle Instruments, in the beginning of this work. 4 38 NEEDLE INSTRUMENTS. As there stated, the Plain and Vernier Compasses and the Ver- nier Transit depend for their accuracy and value, mainly upon the perfection of movement, of the magnetic needle. With such instruments, the greater part of the surveymg in our country has been, and will for a long time in the future, con- tinue to be done. With the improvements made in these instruments, a good sur- veyor may, with great care and skill, do work with a surpris- ing degree of accuracy and perfection, and yet all needles are liable to many irregularities. Imperfections of the Needle. These may arise either from the loss of magnetic virtue in the poles, the blunting of the centre pin, or the attraction exerted upon it by bodies of iron whose presence may be entirely unsus- pected. : The two first of these errors may be easily remedied in the manner we have described. Locan Arrraction.—This third and most frequent source of inaccuracy, may be detected by taking back sights as well as fore sights upon every line run with the needle, and by the agreement of the bearings the true direction of the line is determined. Sometimes a compass may have little particles of iron concealed within the surface of the metal circle or plates. It is the business of the maker to examine every instrument, in search of this defect, by trying the reversion of the needle upon all points of the divided circle. If the needle should fail to reverse when the compass is turned half around and the sights directed a second time upon any object, the instrument should be thrown aside and never sold. Besides the difficulties caused by the above imperfections, the variation of the needle is a frequent source of annoyance. What is termed the secular variation, we have already men- tioned in our account of the Vernier Compass, we will now speak of the NEEDLE INSTRUMENTS. 89 Drurnat Varration.—This is caused by the influence of the sun, which in summer will cause the needle to vary from ten to fifteen minutes in a few hours, when exposed to its fullest influence. To guard against these causes of inaccuracy in the use of ‘needle instruments, the surveyor will need the greatest care and attention; and yet, with all the precautions that can be suggested, the difficulty of measuring horizontal angles with certainty and to a sufficient degree of minuteness by the needle alone, has caused a demand to be felt more and more sensibly in all parts of the country for instruments, in the use of which, the surveyor may proceed with assured accuracy and precision. Indeed, in Canada, so great is the distrust of needle instru- ments, that the Provincial Land Surveyors are forbidden to use an instrument in their land surveys, unless it is capable of taking angles independently of the needle. To supply the demand thus created for increased perfection in the implements of the surveyor, we manufacture a variety of in- struments: two of which we shall now describe, under the names of The Railroad Compass, and The Surveyors’ Transit, SURVEYING INSTRUMENTS. THE RAIL ROAD COMPASS. Fig. 10. As shown in Fig. 10, this instrament has the main plate, levels, sights, and needle of the ordinary instrument, but is also provided with a circle on the outside of the compass box, divided all around and reading by two opposite verniers to single minutes of a degree. The opening through which the divided circle and verniers are seen, are closed by plates of glass, so as to effectually exclude the dust and moisture; the openings are now made on the sides, at~ right. angles to the position they oceupy in the cut, in order to read the divisions with greater convenience, THE RAIL ROAD COMPASS. Al The verniers are fixed to the main plate, and this, by a contri- vance of our own invention, has long sockets which give it great stability, and a motion around the circle almost perfectly free from friction. In this arrangement, the compass circle is very firmly attached to the socket, of which the lower part only is seen in the cut. The yvernier or main plate moves around the divided circle or limb, the divisions on both vernier and limb being horizontal and in the same plane. There is also, béneath the main plate, a clamp and tangent movement, by which, after the main plate has been moved nearly in position by the hand, it can be clamped to the socket, then with the tangent screw, the verniers, are moved slowly around the limb, and the sights fixed upon the desired object with the greatest precision. The graduated circle or limb is divided to half degrees, and figured in two rows, viz: from 0° to 90°, and from 0° to 360° ; sometimes but a single series is used, and then the figures run from 0° to 360°, or from 0° to 180° on each side. The figuring, which is the same upon this as in the other angu- lar instruments we shall hereafter describe, is varied according to the taste of the engineer, the first method is our usual practice. Tut VeERNtERS are double, having on each side of the zero mark thirty equal divisions, corresponding precisely with twenty- nine half degrees on the limb. They thus read to single minutes, and the number passed over is counted from the zero mark in the same direction in which the vernier is moved. The use of two opposite verniers in this and other mstruments gives the means of “ cross questioning” the graduations, the per- fection with which they are centered, and the dependence which ean be placed on the accuracy of the angles indicated. The movement of the vernier plate with the sights attached around the compass circle, gives the surveyor the power of laying 4% 7 49, THE RAIL ROAD COMPASS. off the variation of the needle, while the graduated circle enables him to take horizontal angles with great accuracy, and minute- ness entirely independent of the needle. Tur Nerepte of this instrument is about five and a half inches long, and made precisely like those previously described. Tur Apsustments of this instrument, with which the surveyor will have to do, have been already described. To use the Rail Road Compass. It can be set upon the common compass ball, or still better, the tangent ball already described, placed either in a jacob-staff socket, or, as most surveyors prefer, in a compass tripod. We have also adapted to many of these instruments, the level- ing tripod head, with clamp and tangent movement described on page 46, and this is preferable to any other support. To take Horizonran AneLES.—First level the plate, and set the limb at zero, fix the sights upon one of the objects selected, and clamping the whole instrument firmly to the spindle, un- clamp the vernier plate and turn it with the hand, until the sights are brought nearly upon the second object; then clamp to the limb, and with the tangent screw fix them precisely upon if. The number of degrees and minutes read off by the vernier, will give the angle between the two objects taken from the centre of the instrument. It will be understood that the horizontal angles can be taken in any position of the verniers, with reference to the zero point of the limb; we have given that above as being the usual method and liable to the fewest errors. It is advisable where great accuracy is required, in this and other instruments furnished with two verniers, to obtain the read- ings of the limb from both, add the two together and halve their sum; the result will be the mean of the two readings, and the true angle between the points observed. THE RAIL ROAD COMPASS. 43 Such a course is especially necessary when the readings of the verniers essentially disagree, as may sometimes happen when the instrument has been injured by an accident. TO TURN OFF THE VARIATION OF THE NEEDLE.—Having leveled the instrument, set the limb at zero, and place the sights upon the old line, note the reading of the needle, and make it agree with that given in the field notes of the former survey, by turning the whole instrument upon its spindle. Now clamp to the spindle, unclamp the vernier plate and again fix the sights upon the old lme; the number of degrees or minutes passed over by the vernier, will be the change of variation in the interval between the two surveys. To Survey with this instrument, the opeeator should fix the south side of the compass face, towards that end of the main plate which has the spirit level placed cross wise, and having brought the zeros of the limb, and vernier plate in contact, clamp them, and proceed as directed in our aecount of the Vernier Compass. Of course, it will be understood that lines can be run and angles measured, by the divided limb and verniers, entirely independent of the needle, which in localities where local attraction is mani- fested is very serviceable. The accuracy and minuteness of the horizontal angles, indicated by this instrument, together with its perfect adaption to all the purposes to which the Vernier Compass can be applied, have brought it into use in many localities, where the land is so valuable as to require more careful surveys than are practicable with a needle instrument. SURVEYING INSTRUMENTS. . THE SURVEYOR’ TRANSIT. Figs “V1. The Surveyors’ Transit, of which the above cut is a represen-. tation, is in principle, very similar to the instrument just described, Ronde from it mainly in the substitution of the telescope with its appendages, for the ordinary compass sights. THE SURVEYORS’ TRANSIT. 45 Tue TELEscorr is of somewhat finer quality than that used with the Vernier Transit; as here shown, it is furnished with a small level, having a ground bubble tube and a scale ; sometimes also a vertical circle is connected with its axis, Ture STanparps are made precisely like those of the Vernier Transit, the bearings of the axis of the telescope being conical and fitted with the utmost nicety ; there is also m one of them the movable piece for the adjustment of the wires to the tracing of a vertical line. Tur Spirit Levets are placed above the upper surface of the vernier plate, one being fixed on the standard so as not to obstruct the light which falls on the vernier opening beneath. Both levels are adjustable with the ordimary steel pin. Tur Neep ir, like that of the previous instrument, is five and a half inches long. THe Vernier Prats, which carries the verniers and telescope, is made to move with perfect ease and stability around the gradu- ated circle or limb, attached to the compass box, thus allowing the telescope and verniers to be set to any variation of the needle, and turn off horizontal angles m any direction. Tue VeERNIERS, as in all our angular instruments, are double reading either way from the centre mark, and to single minutes of a degree. There are two verniers placed on opposite sides of the imstru- ment at right angles to the telescope; only one of these is shown in the cut. Tur Divipep Circte or limb is graduated to half debrees, reads to minutes by the verniers, and is figured as described in our account of the previous instrument. Tur Cramp anp TanceNT movement of the vernier plate is the same as that of the Rail Road Compass; it is partly shown in the figure. Tue Trirop Hrav.—tThis instrument should always be used on a leveling tripod. 46 THE SURVEYORS’ TRANSIT. The one shown in the cut, and which is termed the Light Level- ing Tripod, has the upper parallel plate thickened on its under side, so as to give a long bearing for the four leveling screws. , The under plate supports the feet of the screws, and has beneath a cavity or bowl, in which moves a hemispherical nut screwed to the spindle of the tripod. This nut serves both to connect the plates together, and as a support on which the upper plate is moved by the- leveling SCreWS. The under parallel plate has also a screw on the under side, by which the tripod head may be disconnected from the legs, and packed in a box with the instrument. The leveling screws are made of bell metal, have a large double milled head and a deep screw of about forty threads to the inch ; their ends set into little brass cups, so that the screws are worked without indenting the under plate. Sometimes a piece of leather. is put in place of the cups. When the screws are loosened, the upper plate can be shifted around, so as to bring the leveling screws in any position with reference to the plates and telescope of the instrument. The clamp and tangent screws are seen on the upper plate of the tripod. The spindle of this tripod head rises above the upper plate, and the instrument can be removed from it, by pulling out a little pin made to spring into a groove, and thus keep the instrument — from falling when the tripod is carried upon the shoulder. In the lower end of the spindle and underneath the plates, is screwed the loop for attaching the string of the plumb-bob. In the operation of leveling the tripod, the engineer takes hold of the opposite screw heads with the thumb and fore finger of each hand, and turning both thumbs in or out, as may be necessary, raises one side of the upper parallel plate and depresses the other until the desired correction is made. THE SURVEYORS’ TRANSIT. 47 To Adjust the Surveyors’ Transit. Tue LEVELS are adjusted with a steel pin as those of the Ver- nier Transit, and it need only be added here, that in this as well as Oiher instuments having two plates moving upon sockets inde- pendent of each other, the levels, when adjusted on one plate, should still keep their position when both are clamped together and turned upon a common socket. Otherwise, however accurately the telescope might trace a ver- tical line, when revolved upon the socket of one plate, it would give a very different result as soon as the position of the other plate was changed. THe NEEDLE and telescope with its other attachments being ad- justed, as described in our account of the Vernier Transit, we shall here consider only that of the Levet on TrLescorr.—For the adjustment of this attachment we shall give two methods, the first bemg that usually prac- tised by us: 1. First level the instrument carefully, and with the clamp and tangent movement to the axis, make the telescope horizontal as near as may be with the eye, then having the line of collimation previously adjusted, find or place some good object. at a conve- nient distance, say from one to three hundred feet, which the hori¥ zontal wire will bisect; then, without moving the telescope, tarn the instrument upon the spindle, and with the same wire find or place another object in the opposite direction, and at the same distance from the instrument as the first point selected. These two points will be in the same horizontal line, however much the telescope may be out of level. Having determined these, and still retaining them, remove the instrument one or two hundred feet to one side of either of these points, level it again and bring the wires upon the nearest object. Then turn the instrument in the direction of the other, and note the position of the horizontal wire. If it does not bisect the point, the telescope is not horizontal, and the wire must be carried back over half the error, by moving 48 THE SURVEYORS’ TRANSIT. the telescope with the tangent screw. When this has been done, the engineer needs only to alter the position of the level, by the little nuts at the ends, until the bubble is brought into the centre of the tube, when, if the telescope has not been moved from the point where it was fixed, the adjustment will be completed. 2. Choose a piece of ground nearly level, and having set the instrument firmly, level the plates carefully, aud bring the bubble of the telescope into the centre with the tangent screw. Measure in any direction from the instrument, from one to three hundred ~ feet, and drive a stake, und on the stake set a staff and note the height cut by the horizontal wire, then take the same distance’ from the instrument in an opposite direction and drive another stake. On that stake set the staff and note the height cut by the wire when the telescope is turned in that direction. The difference of the two observations is evidently the differ. ence of level of the two stakes. Set the instrument over the lowest stake, or that upon which the greatest height was indicated, and bring the levels on the plates and telescope into adjustment as at first. Then, with the staff measure the perpendicular distance from . the top of the stake to the centre of the eye-piece; from that dis: tance subtract the difference of level between the two stakes, and mark the point on the staff thus found; place the staff on the other stake, and with the tangent screw bring the horizontal wire to the mark just found, and the line will be level. The telescope now being level, bring the bubble of the level into the centre, by turning the little nuts at the ends of the tube, and noting again if the wires cut the point on the staff; screw up © the nuts firmly and the adjustment will be completed. With such a level carefully adjusted, the engineer by taking equal fore and back sights, can run horizontal lines with great rapidity, anda good degree of accuracy. * THE SURVEYORS’ TRANSIT. 49 To use the Surveyors’ Transit. In surveying with this instrument, the plates must be set so that the zeros of the circle and the verniers correspond, and firmly clamped together, the south end of the compass face being turned towards the eye end of the telescope when it is in the position shown in Fig. 11. The surveyor may then proceed precisely as with the plain compass, ; To TurN orr AnNGLES.— When angles are to be measured inde- pendently of the needle, proceed precisely as directed in the description of the Rail Road Compass. The variation of the needle is also set off as mentioned in our account of that instrument. ; Sizes of the Surveyors’ Transit. We mike two sizes of the Surveyors’ Transit; the largest re- presented in the cut, having a needle five and a half inches long, a limb of seven inches diameter, and weighing from twelve to thirteen pounds, with the tripod head attached. The smaller instrument, has a four inch needle, a limb of six inches, and is about one-fourth lighter. The larger size is more generally preferred, on account of the greater length of the needle, which renders it more sensitive, and better adapted to the purpose of the surveyor. Merits of the Surveyors’ Transit. In this instrument, as just described, the surveyor will recog- nize advantages not possessed by any other instrument with which we are acquainted. Having a long needle, it is excellent merely as a needle instru- ment, and combining also all the advantages of a telescope with the accuracy of a divided limb and verniers, and having also the means for turning off the variation of the needle, it is for a mixed practice of accurate surveying and engineering, such indeed as is required of most city engineers, the best instrument ever constructed. 5 50 THE SURVEYORS’ TRANSIT. The arrangement of the sockets which we have alluded to in our account of the Rail Road Compass, is very perfect and stable, and the movement of the plates almost entirely free from friction. We made the first of our Surveyors’ Transits about three years ago, and, from that time to this, have found their sale continually increasing, and those that have been in use satisfying imvariably the best expectations of the purchaser. The peculiar construction of the sockets and plates of this in- strument are entirely our own invention, and we feel the utmost confidence in recommending it to all whose practice is such as to require the use of the needle combined with that of the divided circle and yerniers. ENGINEERS’ INSTRUMENTS. THE ENGINEERS’ TRANSIT. Fig. 12. Having now described the various instruments employed in sur- veying, we shall consider those whose use belongs more especially to the practice of the civil engineer, and of these the first in im. portance is that termed the Engineers’ Transit. D2 THE ENGINEERS’ TRANSIT. It differs from the instrument just described in having the com- pass circle, verniers and standards, attached to the same plate and moving together above the divided circle or limb, The cut, Fig. 12, shows the general arrangement of the parts, a detailed description of which we will now proceed to give. Tue TreLescore is from twelve to thirteen inches long, having an object glass of one and three-eighths of an inch aperture, an eye-piece of very high magnifying power, and is of the finest quality. Like all those of our own instruments, it is capable of reversion only at the object end, though we have often, when desired, made the other or even both ends to reverse. . The rack and pinion movement of the object glass is usually placed, as shown on the top of the telescope tube, though some- times on the side, as the engineer may prefer. Pryton ro Hye Guass.— We have often adapted to the eye- piece’ of this and our other Transits, a rack and pinion movement which is placed on the side of the tube and is very excellent in bringing the cross wires precisely into focus. * Tue SHapre.— - sioleterste Nid King puis, 25 Svie-c% se stasioreeate oly ale God ela 1 at shale aiaietaanteiataes Siac Masons) evel cvcecehicote sate ces eee 6 val Me eRe ieioe ses Miierom eer ls sia cers. oso ecertepetel paiers ao see io! bonis) ¢ 0 0 econ eens . GO 16 IWSOLEAG, .de-5 2's, d:0:shaie, s-or0/s, ors ahegerelert Deny Mhalseeata ey d sJeletaroiars 4 fs how, remagnetized.. 2 isst0. <..6c.. eeicie om eneeaiee ee < Variation: of diurnal; s-s../ssia cere serele Rie eters Sate “ s i $$ speCTlAar, ..siyieuSceo obe eke Semele 5 imperfections Off. ....6 6 ni. os vale sess cele Widedle: instrpmentere wil (0. ders eos o's 0 sore oleie recipe aici ia eeamaene Object glass, how composed,..........seeceeeoes < Aateare o's wake tf slide Bow. SO} UstOd, .~ «ie leia¢ olnie Carte niains on 5 Seles Parallax instrumental jccriysciese\sicls cleyereteretereaeieretre siete volre agile tf IO WHAV OLUOA se Liem o's c ieee tee eta nearest eavens Sate ae ee Paar. 85 11 19 31 36 71 12 37 16 53 7 12 46 59 72 72 62 16 TABLE OF CONTENTS. MIO SEIBESY Soda dived dune sin e o\etssie'.s6 urs bee cle sect sys 3% PRADO COMPAS) 6s. os oes sa oie enna AG Sine rst iid SURES NOW Gon Repairs of Compass, how made,..........+++eeeees Srey sabes hoes - se SoVornier Lransit,... 5... 0. MOS Cet cine. elas neta ts Sights of Compass,............+- act Caster kro ee Ret ears ae BEE SABTR Dyic: re 5c. 070 60 6's 5 HO goeAb OGS So erercastoKere A tic PE 6 Sa on telescope, . .. 6%... Srafelele's win iefd ocsltus Spires ew sinls oie IEEE OAVSIOB ye as ops moe 658 Sin op Se nce abe oie swt Essie Sensitiveness of a level bubble, degree of,.............e0e scene IERCERTOIESEODGI le cioieic s <2 ole ee vine 086 veins a s.r w\sic'e 0 e/3\es'inie Fe Spring, Catch,.......... SERIOR OS ARCO SC COLO DEO en bya ohitoger ar okets Tangent Scale on sights,............4. sipreteeycisseletctetst jal ere, cieisere : Telescope of transit, sectional view of,...... OF oes 9 © sielelsiale vine Ss pie level, S bic ae ers eh ae “ magnifying power of, how ascertained,............+- ‘« optical principles of,.......- Rus cbdoweoenet aa oose: BRMMATUUVOPUIGT Soha <'s'5. coo ce ne nerscce ess nope ts Soles eat seaieke Some BULVEY OTS, .... 0s s sepa SEO REEDED CLL CO OSS SORE bar =) -engmeers),...'...2...+ ASD SO UTOD daa Sb RLOt Ie CASS Tripod head, light,............ be Be Hie Vetewneis Camera % BMMEMOR VY 5 oc cco .0 ss 0b oman, 20/6 teed ne Goldin eo 0a 48 sinere SUMING EHIOFONG.S1Z69 Of, 6. 5.00%. vce e cinedcciceescee cos ae Two telescope instrument,.......... pike: et nite, *) eee 8 SECS Theodolite axis,...... Ra siavoitreyeze eictereisiete 1s etal UR yore Street CINE sig s'ms oo < no 3 60's patesets AGO Oc > cae aiaseteteconal crete Tapes, measuring, steel and metallic,............ ee ck ONE ee Wertieal CIPCle:. ....0seces ae sire, scapes tier oVersicl esis ae ose eheveo yrs é Vernier of compass,...... Sele heens sigaidiacgi er aers eseeees wisleje'ee es 7 a OG, ss how read,........ BARONE oot cis araane lelest ens NINE SREIIO DIG eriiate > ain oo anise sr5.ec ails ee oc 0 vice on o,0\0.cieinyo.es OUR erie: cas sos viess cect aos sais ocicc ve cs eet » i= SUPPLE MENT TO MANUAL, DRAWING INSTRUME NTS. To guide the surveyor aud engineer in the selection of Drawing Instruments, we here add a detailed description, with illustrations and prices of the separate pieces, and cases of the different kinds in general use. Those we shall first mention are of German and French manu- facture, are of good quality and finish, and such as the great ma- jority of purchasers select and use. . The Swiss instruments are of better quality and finish, and are held at much higher rates. The prices given with all the instruments described are the same as those of other importers. FRENCH AND GERMAN INSTRUMENTS. II DRAWING INSTRUMENTS. FIGURE. PRICE, 1. Brass Dividers, brass joints, rivet-heads, 5 inch 12 cts.,6inch $0,18 Laer ae Bu steel joints, screw-heads, 5 inch 25 ets., 6 inch sou 1. Fine Dividers, steel joints, turned cheeks, 4 inch 50 ets., 5 inch 62 cts, 6 inch, - - - - - - - - s75 2. Fine Dividers, steel joints, hair spring, 5 inch $1,00, 6 inch, 1,37 Daas Re iY «superior, 5 inch $1,837, 6inch 1,75 1. German Silver, steel joints, turned cheeks, superior, 5inch, - 15 L, x SF sf & se 6ineh, - 87 2 S as és hair spring, fine, 5 inch $1,50, Gineh 1,75 9, x i 4 “superior, 5 inch $1,75, 6 inch ~ 2,00 3. Three legged Dividers, brass, $2,62, Ger. Silver $2,75, to - 8,50 Bisecting, - - - - - - - - - ,50 4, Pocket Dividers, German Silver, - - E S = 2,00 5. Proportional Compasses, brass, $1,50 to $3; full divided $7 to 8,50 5. ae os German Silver, $7,25 to - - 9,00 6. Pillar Compasses, brass $5,50 and $5,75, Ger. Silver $6,75 and 6,00 7. Dividers, bfass, 3 inch, with pen and pencil point, med. quality, 1,25 ~ ly Ger. Silver, “ < & fine . 2,50 8 9 8. Dividers, brass, 5 inch, med. quality, with pen and pencil point, ,75 6 inch, . - - - - - - 87 8. ss « 5 inch, med. quality, with addition of length- ening bar, - - - - - - - - - 87 8. Dividers, German Silver, 6 inch, fine quality, pen, pencil, bar _ and needle point, - - - - - - - 8,25 9. Furniture for Beam Compasses, brass, $3; with adjusting screw, 3,75 9. ae Seas German Silver, $4,25 to - 5,00 + »~ 4 DRAWING INSTRUMENTS. III BOW PENS AND PENCILS, SPACING DIVIDERS AND DRAWING PENS. 12 FIGURE. PRICE. 10. Bow Pens, brass, 50 cts. to - - - - - - $1,25 dig 2S “with joint in each leg, German Silver, - - 2,25 Bow Pencils, <“‘ oC ts 8 sé - - 2:25 12. Bow Pens, with adjusting screw, brass $1,25; German Silver, — 1,50 Le as * Ly & “and hinge to pen, brass, - 1,50 German Silver, - - - - - - - - 2,00 12. Bow Pens and adj. screw and pencil point, German Silver, 2,25 12. Bow Pens with adjusting screw, German Silver, with pencil and needle point and extra pen point, - - - 3,50 13. Bow Pencils, solid steel German Silver or Ivory handies, — - 1,75 14. Spacing dividers, “ Ki a - 1,50 15. Bow Pens, % $6 e g - 1S 16, Drawing Pens, 25, 87 and - - - - - - 300 17. as “ with hinge, - - - - - - ,50 lie if Ses oats “« and protracting pin, 62 and - a) rh a € sf “extra fine, - - - - 1,25 17. a «all German Silver for red ink, : - Bil 18. us “double or Railroad Pens, $1,75 and - 2,50 19. Roulettes, for dotting lines, 50, 62 and - : = 2 s75 TV, DRAWING INSTRUMENTS. SQUARES, PROTRACTORS, &C FIGURE, 22, 23 20, Brass Protractors, assorted sizes, 124 ets. to - - “f « with steel blade, 2 to 8 feet long, - German Silver Protractors, with horn centre and movable arm, divided to 4 degrees, $4 to - - > German Sipord -rotractors, whole circle, horn centre and mo- vable arm, divided to + devrees, $4,75 to - =i Horn Protractors, 4 inch 124 cts, 5 inch 25 ets, 6 inch - Tvory Protractors for Engineers, 6 inch $1,50, $2, $2,50 and es He > oy 2} inch wide, very superior, 6 inches long, $3,50 and - - - - Tyory Protractors for Engineers, 12 inch extra wide and full, Ivory Seales, 6 inch usnal quality, - - . [very Seales, 12 inch, chain on edge only, 20x40, 30x50, 40x60 $2.25 to - - - - - - Toon Seales, 12 inch, chain on edge only, 50x109, - ¥ os 12 inch, for Architects, 2 2525, 2,50, -3,00sand «2 = Ivory Seales, 12 inch, 16 scales off edge, in tenths or twelfths, $3,50 and - - : - Boxwood Seales, 6 inch, usual quality, - - - ee Protracting Seales, 6 inch, - - - if Seales, 12 inch chain, 10 to 60 on edge. - - Hs “ 42 inch, 16 scales off edge in tenths and twelfths, ne “12 inch Architects, graduated from $ to 8 inches, “ce ce 3 sided chain, giving 6 scales all on edge, —- Boxwood Seales, 3 sided Architects, giving 12 scales all on edge, $2,50 to - 2 3 2 PRICE. $1,50 7,50 6,50 DRAWING INSTRUMENTS. Vv FIGURE. PRICE. - 23. Boxwood Gunter Seales 1 foot 87 and 75 cts, 2 feet - s15 o Pocket Rules, 1 foot, 4 fold, 25 to 75 ets, Ivory do, 62 ets. to - - - - - - 2,00 Paper Scales 18 inches long, in sets of six, graduated from 4 to 3 inches, per set - : : 3s : 1,25 28 © © 24 25 26 24. T Squares, wood, with arm, 18 to 30 inches long, - $0,75 0 i sf sf «* and swivel head, - - 1425 Bee sh $f ee a aD * and brass edges to arm, $1,75 to - - - - - 2,50 25. Irregular Curves, various sizes, 25 to 87 and - 00 26. Ebony Triangles, 87 cts, Pear wood do. 3 - 20 27, German Silver Squares and Triangles, 50 cts, to - 2,50 28. Pins to fasten paper to the drawing board, brass, 25, 87 and 50 cts. German Silver, per dozen, - - . ,60 29. Horn Centres, to prevent the dividers from marking the paper, ,18 VI “DRAWING INSTRUMENTS. FIGURE. PRIOR. 80. Parallel Rules, Ebony, 6 inch 87 ets, 9 in, 62,12 in..75, 15 in. —$1,00 80. ff « —“Tvery, 6inch, - - Tee aim 100 30. ae ‘Brass, fine, 9 in. $1,75, 12 in. 2,50, 16 in. * 3,12 st Ae “on rollers, 9 inch $4,25, 12 inch, ee ie fr) es «eo Ebony, *-12- in. 2,624 5 in 837 sae.! 4,00 ‘S “Ivory, “ . graduated edges, 12 in, “9 4,20 18 inch, : > 2 : - . 6,00 31. Pentagraphs of Ebony, very accurately made, - 14,00 82 pe of Brass, » “ us Ss . 22,00 CASES OF MATHEMATICAL DRAWING INSTRUMENTS. 53. No. 636, Morocco ease—small German Silver Instruments— Needle point, 4 inch dividers, fine quality, . pe dabG 35. No. 25, wood box, brass instruments, without needle points, medium quality, - - - - 1,25 34. No. 82, wood box, brass instruments, 5 inch dividers, medium - quality, box scale, 4 aie - - 1,75 ot, No. 88, wood box, brass instruments, 6 inch dividers, medium ~ quality, Ivory seale, - - - - sey A) 34. No. 600, Morocco, brass instruments, common quality, box protractor, (fig, 22), ; - : : 1,75 5é. No. 154, Moroéeo, German Silver instruments, fine quality, At Ivory protractor, (fig. 22), - - 3,50 35. No. 054, Moroceo, German Silver instruments, with addition of lengthening bar, - * - ‘ $4,95 a5 ° a ih ary . Co pve e . * 35. No. 645, Morocco, German Silver instruments, without plain dividers, - - - - Coe 00 : ~ , DRAWING INSTRUMENTS. Vil "FIGURE. PRICE, 35. No. 023, Morocco box, brass instruments, good quality, . 2,50 85. No. 599, do do do do common quality, box 3 protractor, ‘ . - - : 1,25 36. No. 786, Morocco box, German Silver instruments, fine quality Tyory protractor, - . - 6,50 87, No. 745, Morocco box, German Silver instruments, fine quality, 6,50 WL, a RY 4 88 88. No. 15, wood box, brass instruments, medium quality, 8,50 ms od. do - 29, do do do needle points, med. qual. 3,75 "39, do. 89; do do do do with bow pen, 4,25 5 a 39. No. 40, wood box, brass instruments, needle points, with bow ee. si pen and proportional compasses, - - $6,00 a : 89. No. 535, Morocco case, brass instruments, fine quality, "$50 VIII DRAWING INSTRUMENTS, Prose L FIGURE. 4() > AT 40. No, 805, wood box, German Silver Instruments, fine quality, 40. do 535, do do do with bow pen, 40. do 036, do do do do do and hair dividers, - - - 41. do 845, wood box, German Silver instruments, fine quality, 41, do 655, do do do with addition of Railroad Pen, (fig. 18) - 2 : 41, do 455, wood box, lock and key, superior quality, without the proportional compasses, but with double drawing pen, (fig. 18) and additional pen, (fig. 17) - 41. do 126, wood box, lock and key, German Silver instruments, superior quality, with addition of Railroad Pen, (fig. 18) and one Pen, (fig. 17) : - Sie do 826, Sameas No. 126, but with addition of furniture for Beam Compasses, (fig. 9) - - é 41 42. No. 5, Fish skin cases, brass instruments, box scale, - _ do55, do do do do Ivory seale, - do 57, — do do do do Ivory scale, steel joints, 2,50 2,75 3,00 “* RIGURE. PRICE, _ No. 1 A, Drawing Compass, joints in legs, 64 t0 7 inches long, with ; pen, pencil-holder, needle pt,lengthening bar and dot. pen, $6,00 No. 1 B, Drawing Compass, 6 inches long, with pen, pencil-holder, r lengthening bar and needle point, - - 4,75 9, Hair Spring Divider, 5-6 inch, = - 2,00 _* 8, Plain Divider, 44 inch, - - - 1,374 3. do do 5-6 do - - - 1,50 4, Uair do 44 do - - - 1,75 5, Drawing Compass, 4 in., with pen, pencil holder and needle pt. 38,75 - 6, The same, without the needle point, - - 3,00 x SWISS INSTRUMENTS. FIGURE, . Proportional Compass, with full division for lines and circles, 1. The same, with Micrometer Screw, - - ‘8. Beam Compass, 19-20 inches long, in 2 German Silver bars, ' 8. The same, 20 inches long, in 8 German Silver bars, 8. do do 86 do do 4 do do do 8. 1d do = 48 odo do 4 do do do 9. Triangular Compass, ° - - 10. Dotting Pen, - - = ee 11. Road Pen, - - - - 12. Pocket Divider, . - - 8. Whole and Half Divider, - - - 15. 16. 17. 18. 19, 20. 21. . 14 A, Universal Compass, with points to shift, - . 14 B, Universal Compass, with points to turn, . Large Steel Spring Divider, - - - Small Steel Stepping Divider, - - Small Steel Compass, with Pen, ria os - Drawing Pen, with joint 44 inches long, - do do do 54 do = = do do do ~ 6 do - - Horn Centre, with German Silver frame, : SWISS INSTRUMENTS. XI FIGURE, : PRICE. é 22, Bow Pen, : 4 ; : 1,80 23. Bow Pen, with pencil holder, : ’ 2 2,50 94, German Silver Centre, with handle, : 4 ee 25. German Silver Paper Pins, per doz., - = 50 25. Steel do do do - - ,60 A No. 26, Calliper, : é ‘ - 5,00 6: ae do English pattern, with two verniers, - 7,00 21, Eccentric Rule, < ee 28. Protractor, 44 inch diameter, whole degrees, - 1,25 ~ 28. do 5+ do half do i 1,50 » 928. do 6 do half do - 1,62 “98. do 64 do quarter do E 2,50 Horn Protractors, from 25 to 2 : 2 ,50 _ 28. Circular Protractor with arm, 8 inch diameter, quarter degrees, 8,00 28. do do do 10% “doar do do 10,50 TCs Nan ae (OT Csi dies Mn Pi ot Ma ee Tae TL Vuh aloe 29 Circular Protractor with vernier, 8 inch diam., quarter deg. 12,00 do do do 10 do do 13,00 X= SWISS INSTRUMENTS. FIGURE. PRICE, 29. Half Circle Protractor with vernier, 54 inch diam., half deg. $7,50 29. do do do 8 do quarter do 9,00 30. Beam Compass furniture, for wood beams, - 5,00 — 81, 88 and 34. Horn Curves, each _ - 50! 82. Drawing Compass, 4 inches, with long ivory handle, spring, ' and micrometer, with 2 pens, pencil holder and needle pt., 5,00 35. Parallel Rule, with rollers, - - * 9,00 86. Protractor Seale, divided to 4°, _ - 215 86. - do do do 4°, - - 8,75 A No. 87. Bow Compass, fast needle point and pen, with joints in both legs, - = _ 2,00. B No. 87. Bow See fast needle point and pencil holder, with joints in both leg - - - 2,00 . 88. Lengthening ee - - - 12,00 Persons desiring a complete Case have but to name the vehi of the N Instruments they want in the Box. The price of the Box is always according to the size and finish, 3 the. | same, Raa 4