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U. S. DEPARTMENT OF AGRICULTURE. 
 
 WEATHER BUREAU. 
 
 INSTRUCTIONS 
 
 FOR 
 
 Obtaining and Transcribing Records from 
 Recording Instruments. 
 
 CIRCULAR A, INSTRUMENT ROQM. 
 Revised Editjon. 
 
 PREPARED UNBJCR DIRECTION OF 
 
 THECHIEF OK-ll HE WEATHER BUREAU 
 
 C. F\ MARVIN, 
 
 Profeitor of Meteorology. 
 
 PUBLISHED BY AUTHORITY OF THE SECRETARY OF AflRlClJlTIJBE. 
 
 , WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 "1-89 4. 
 
Cornell University 
 Library 
 
 The original of this book is in 
 the Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924003566688 
 
U. S. DEPARTMENT OF AGRICULTURE. 
 
 WEATHER BUREAU. 
 
 INSTRUCTIONS 
 
 FOE 
 
 Obtaining and Transcribing Records from 
 Recording Instruments. 
 
 CIRCULAR A, INSTRUMENT ROOM. 
 
 Revised Edition. 
 
 PREPARED UNDER DIRECTION OP 
 
 THE CHIEF OF THE WEATHER BUREAU 
 
 BY 
 
 C. F\ MARVIN, 
 
 Professor of Meteorology. 
 
 PUBLISHED BV AUTHORITY OF THK SECRETARY OF AGRICULTURE. 
 
 WASHINGTON: 
 
 GOVERNMENT PRINTING OFFICE. 
 1894. 
 
LETTER OF TRANSMITTAL. 
 
 U. S. Department of Agriculture, 
 
 Weather Bureau, 
 Washington, D. C, October 2, 1894. 
 Sir : I have the honor to transmit herewith manuscript copy for a 
 new and revised edition of Circular A, Instrument Eoom, containing 
 instructions to observers of the Weather Bureau relative to the proper 
 manner of compiling and transcribing meteorological data from record- 
 ing instruments, and to request that the same be published. 
 The first edition, printed in 1892, has become exhausted. 
 Very respectfully, 
 
 Mark W. Harrington, 
 Chief of Weather Bureau. 
 Hon. J. Sterling Morton, 
 
 Secretary of Agriculture. 
 
SPECIAL INSTRUCTIONS. 
 
 The rapid increase in the number and variety of the continuously 
 recording meteorological instruments in use at the stations of the 
 Weather Bureau necessitates increased vigilance on the part of observ- 
 ers having any of these instruments in charge, that loss of records and 
 other defects do not occur. The Chief of the Weather Bureau feels con- 
 strained to impress, emphatically, upon each observer the great impor- 
 tance of presenting only plain and unaltered facts in both the ordinary 
 regular observational data and also in record sheets from automatic 
 instruments and tabular data compiled therefrom. 
 
 Any portion of these records may be required in courts of justice, 
 and, by decision of the Supreme Court of the United States, is admis- 
 sible as evidence. 
 
 The object of paramount importance is to secure the highest attain- 
 able degree of accuracy, and no effort is spared at this office to dis- 
 cover and eliminate, as far as possible, the effects of all occasional 
 and accidental imperfections and interruptions in automatic records 
 and the usual mistakes of calculation, inattention, etc. 
 
 Any action on the part of observers which tends to conceal the true 
 circumstances, such as attempting to fill in missing records in a man- 
 ner that makes them appear to be automatic and original, is liable to 
 wholly defeat the aim of scientific observation to ascertain the truth, 
 and therefore it is imperative that every modification of the automatic 
 records shall be accompanied by a marginal note plainly stating the 
 facts in the case. 
 
 It is expected that observers will be on the alert not only to prevent 
 the occurrence of errors or imperfections of any kind, but also to dis- 
 cover and remedy defects, and, by special observation, secure such 
 data as may aid in supplying missing records and help to bridge over 
 interruptions. 
 
 The instructions herein are furnished for the guidance of observers in 
 the preparation of records from recording instruments, and will replace 
 and take precedence of all similar instructions heretofore issued. 
 
 Mark W. Harrington, 
 
 Chief of Weather Bureau. 
 
 Washington, D. C, October 2, 1894. 
 
 5 
 
INSTRUCTIONS FOR OBTAINING AND TRANSCRIBING RECORDS FROM 
 RECORDING INSTRUMENTS. 
 
 In all cases of the failure of the instruments to record for a longer or 
 shorter period, it is desired and intended that observers supply the missing 
 data whenever possible, yet this should in no case be done except in such 
 manner as to shoto conspicuously on its face fas, for example, by the use 
 of ink of different color J that this insertion is not a genuine instrumental 
 record. 
 
 Also, if, through a failure or imperfect performance of the clock, or a 
 delay on the part of the observer to properly adjust the instrument or change 
 the slieets at the times required, the instrument makes an abnormal or 
 improperly placed record, such portions should not, under any circum- 
 stances, be erased from the sheet. 
 
 Brief marginal notes of explanation should always be given-. 
 
 Sheets containing imperfect records must never be destroyed, 
 
 NEATNESS REQUIRED IN RECORDS. 
 
 1. When either the triple, double, or single registers are in proper 
 condition and adjustment wind velocities of 90 miles per hour can be 
 recorded without difficulty, but if the pens are neglected and smeared 
 on the outside with ink, or improperly adjusted and forced with excess- 
 ive pressure against the paper, the points soon become worn and 
 clogged with dry ink , dust, and fibers of paper so that lines become 
 heavy and the mile marks merge together at velocities of even 40 miles 
 per hour. 
 
 The blotted, imperfect, and untidy ink records sometimes obtained at 
 stations equipped with automatic instruments using pens can be wholly 
 avoided, and fine, clear records can easily be secured by a little atten- 
 tion to neatness and the exercise of care in the inking and adjustment 
 of pens, as follows : 
 
 2. Pens. Only the special ink provided for registering instruments, 
 such as furnished with barographs or thermographs, should be used. 
 The ink should be replenished daily, and only enough applied to insure 
 a supply during the next twenty-four hours. Avoid smearing the ink 
 upon the outside of the pen and over the nibs by which the pen is 
 secured to the arm. These precautions will, in a measure, prevent an 
 accumulation of dried ink and dust about the sides of the pen. 
 
 7 
 
8 
 
 3. The adjustment of the pen should be such as to injure the light- 
 est possible contact at all parts of the sheet. It is found observers in 
 many cases press thepen entirely too hard against the cylinder, thereby 
 wearing away the point much more rapidly than is necessary, and at 
 the same time clogging it with particles of paper. Be careful to avoid 
 this fault. 
 
 Owing to imperfections in the old single registers the cylinders are 
 not true and a considerable pressure of pens may sometimes be neces- 
 sary to prevent loss of record at certain points. The attention of the 
 office should be called to instruments that are seriously defective in 
 this respect, but the. observer is expected to adjust the register pens 
 with no greater pressure than is actually necessary. The best way to 
 judge of the amount of pressure between the pen and cylinder is to 
 catch a pencil point under the end of the arm ..near the pen so as to lift 
 the- latter slightly a few times from the paper, thus ascertaining the 
 amount of pressure to the spring arm. 
 
 4. The pen arm of single registers should be curved so as to cause 
 the extreme point of the pen only to come in contact with the paper. 
 It is an advantage also to bend a little the pen itself just back of the 
 rounded portion, thus causing the point to touch the paper at a high 
 angle. 
 
 5. To start the flow of ink in a new or freshly filled pen, draw a 
 piece of writing paper carefully between the points so as to wet the 
 faces, but in a manner that will not bend or deform the points or spring 
 them too far apart. 
 
 6. The lateral movement or stroke of the pen should be considerably 
 less than formerly allowed on old register with pencils. One-sixteenth 
 of an inch is ample. A long stroke has a tendency to throw ink from 
 the pen when too much has been added, and cause bad blotches upon 
 the records. This may be partly prevented by inserting a very small 
 fragment of sponge in the end of the pen. The sponge must not be 
 crowded into the pen, but must fit loosely; otherwise, insufficient ink 
 will be absorbed. 
 
 7. Pens cleaned.— -The pens should be removed from the instrument 
 from time to time and thoroughly washed in water, scraping the parts 
 of the pen a little with a knife blade to remove dried sediment from the 
 ink that is not washed off by the water. 
 
 8. In cleaning the pens care must be exercised not to spread or 
 otherwise injure the points. . In order to give satisfactory results these 
 points must be quite sharp, and must very nearly touch each other. 
 Otherwise, too wide a mark will be made on the form and records of 
 high wind velocities will be indistinct. If, after cleaning, the flow of 
 ink does not start, draw the edge of a thin sheet of paper between the 
 points of the pen. 
 
 9. Whenever the pen becomes worn so that a neat and distinct record 
 can not be obtained, replace it by the extra pen kept at station, and 
 
9 
 
 return the old one immediately to this office by mail, in a package 
 marked "Instrument Room," the pen being carefully protected from 
 injury, using regulation mailing case, if possible. When received at 
 this office, the pen will be repaired and returned, or a new one supplied) 
 as occasion may require. In case an extra serviceable pen is not at 
 station, application should be made for one. 
 
 10. Sheets blotted. — In removing the sheet from the cylinder the lat- 
 ter portion of the record will probably not be thoroughly dry, owing to 
 the special properties of the ink, and it is therefore necessary to use 
 care in slipping off the rubber bands, etc., in order to avoid blurring 
 and smearing the record. When removed from the cylinder, sheets 
 should therefore be laid carefully aside to dry or the superfluous ink 
 removed with a blotter: 
 
 11. The barograph and thermograph pens being mounted on flexi- 
 ble springs, are easily set to gentle pressure against the cylinder, but 
 the pens must be cleaned occasionally and every effort made to secure 
 fine, clear lines. 
 
 12. Wind-direction ink pads. — These should be carefully inked, and 
 in such a manner as to avoid smearing the ink over all the adjaeeut 
 parts of the instrument. The quantity should be sufficient to carry 
 the record for twenty-four hours, but not enough to cause bad blurs 
 and blotches next after inking. The pad should be removed from the 
 instrument by withdrawing the pin holding it in place, and the ink then 
 worked into the pad, applying it with slight pressure by a small stick 
 or flattened wire to both the top and under side of the felt, so that the 
 latter is moistened with ink through and through, thus leading to a 
 uniform strength in the record obtained. • 
 
 13. Felt ink pads renewed. — Occasionally the felt of the pad will 
 need to be lowered and the end cut off, or a new piece of cloth inserted. 
 This is easily done by removing the small metal plate covering and 
 holding the pad. New felt can be furnished upon application. 
 
 14. Points of direction arms cleaned. — The points of the direction 
 arms also need occasionally to be cleaned from the accumulations of 
 dust, dried ink, fibers from pad, etc. A brush such as used in clean- 
 ing the typewriter can be employed with advantage, the magnet plate 
 being turned back on its hinge and the ink pad removed, so as to give 
 free access to the points of the direction arms. 
 
 15. Observers can not be too strongly impressed with the impor- 
 tance of keeping recording instruments in a neat and clean condition. 
 The whole question of clean and legible records is simply a question 
 of daily neatness and a little intelligent care and attention. 
 
 RECORDS FROM SINGLE, DOUBLE, AND TRIPLE REGISTERS. 
 
 16. Sheets should be changed as nearly as possible at 12 noon, and the 
 clock regulated to correctly keep seventy-fifth meridian time. Should 
 the sheet be changed after 12 noon, and the clock is correct, the record 
 
10 
 
 will extend beyond the noon line. That portion of the record on the 
 old sheet occurring after 12 noon, correct time, belongs properly on the 
 new sheet, and should be omitted in counting up the record from the old 
 sheet and added to the record from the new sheet. 
 
 17. An effort has been made to have all forms trimmed, except at one 
 end, to exactly fit the various instruments; but as this is difficult to 
 do perfectly in great number, observers should examine each form and, 
 if necessary, trim it to the correct dimensions, as indicated by dotted 
 lines, which may be seen near the edges of imperfect forms. 
 
 18. Sheets should be wrapped closely about the cylinder and held by 
 rubber bands. The pen or pencil should be adjusted laterally so that 
 the point will closely follow the proper line, and start the record on the 
 sheet at the hour and minute corresponding 'as nearly as practicable 
 to the correct time at the moment at which the cylinder is clamped to 
 the clockwork. If pencils are used, about one-eighth of an inch side 
 movement of the point for closure of circuit is considered sufficient. 
 The pencil leads must be kept pointed, and the pressure so regulated 
 that a plain, distinct record may be secured. 
 
 19. Wind direction records centered. — Wind direction records must 
 be carefully centered in the appropriate space on the form, so that the 
 respective arms strike over the corresponding letters upon the sheet. 
 This is readily accomplished by the thumbscrew adjustment attached 
 to the magnet plate of the older forms of registers, and in the latest 
 pattern by slipping the cylinder upon its own axis. The cylinder is 
 held by one hand, and the axis (which must not be clamped to the 
 clock) is revolved by aid of the enlarged portion at the left end of the 
 cylinder until the direction arms are nicely centered over the proper 
 letters on the record sheet. This adjustment can be made at any part 
 of the sheet and the cylinder afterwards turned on its axis up to the 
 noon or any other time line in the ordinary way. This adjustment of 
 the record must be made each day when the sheet is changed, unless, 
 after being once set, a mark is made on the -cylinder at the end of the 
 record sheet and the- new sheets from day to day thereafter placed upon 
 the -cylinder so that their ends come exactly at this mark. 
 
 20. Time adjustment on triple registers. — It is of great importance 
 that the records of the different elements obtained by the triple regis- 
 ter be strictly simultaneous. To test the instrument in this respect 
 set one of the time lines of the cylinder exactly under the points of the 
 wind-direction arms when pressed against'the'paper; the points of the 
 rainfall and velocity pens should fall as nearly as possible upon the 
 same line. Observers will adjust their registers to satisfy this condi- 
 tion as well as they can, calling serious defects to the attention of this 
 office. 
 
 21. The points of the velocity or rainfall and sunshine pens must not 
 be adjusted to follow each other, but must be placed side by side and so 
 that their respective records will be about one-eighth of an inch apart 
 
11 
 
 and at equal distances on either side of the longitudinal spiral lines 
 ruled on the sheet. 
 
 22. Lost motion in record cylinders. — In starting a record sheet, a cor- 
 rect time setting can be obtained only by taking up properly the slack 
 or unavoidable looseness in the connections between the cylinder and 
 the driving clock. The proper setting is secured if the pens indicate 
 correct time, while the finger tip is drawn gently across the flange of 
 the cylinder in such a manner as to tend to rotate it in a direction oppo- 
 site to that in which it normally revolves. (See par. 71, Circular D, 
 Instrument Room.) 
 
 The most accurate adjustment of the record to the correct time is 
 made after the cylinder is clamped to- the clock, by slipping it a little 
 on its axis, just as the hands of a clock are slipped and set as may be 
 desired. 
 
 23. Incomplete records. — Whenever the record is incomplete a margi- 
 nal note must be made explaining the cause; and if the anemometer 
 fails to make a record, the dial should be read as soon after discovering 
 the failure as possible, also at each 8 o'clock observation and at each 
 noon during the incomplete record. A dial reading will again be made 
 when the record is started. These readings, together with the time at 
 which taken, will be entered on the lower margin of the form. 
 
 In case of the loss of record for a period of twenty-four hours or more, 
 blank sheets for the period must be filled up with the name of the sta- 
 tion, dates, and such data as can be obtained, and forwarded with the 
 regular monthly package. 
 
 24. Record sheets, how mailed. — The sheets from 12 noon of the first 
 day of one month to 12 noon of the first day of the succeeding month 
 will be folded and mailed not later than the second day of the month. 
 Forms 1017 must be mailed not later than the fourth day of each mouth. 
 
 25. Register examined.^-The register will be examined frequently. 
 Form 1017 must be mailed not later than the fourth day of the mont h. 
 Every effort will be made to keep the instrument in perfect running 
 order, and the clock regulated to correct time. If a proper record is 
 not secured, observers will endeavor to at once locate and remedy the 
 fault. Should repairs be necessary that can not be made without 
 expense, or should the observer be unable to put the instrument in work- 
 ing order, this office will be immediately informed of the fact by mail. 
 
 26. Current velocity, how obtained from register. — To obtain the cur- 
 rent velocity from the anemometer record, take the number of spaces . 
 and parts of spaces between the mile marks recorded in the five niiu- 
 utes preceding the moment considered and multiply the result by 
 twelve, except when the wind lias blown less than 12 miles and hour, 
 when the velocity for that hour will be determined as shown by the 
 second example below. 
 
 First example: Suppose the number of spaces indicating mile marks 
 between 7: 55 p. m. and 8 p. m. was 1£, then the velocity of the wind 
 to be recorded at 8 p. m. is 1^ x 12 = 15 miles per hour. 
 
12 
 
 Second example: If the interval between the last two mile marks is 
 7 minutes, then the current hourly velocity would be obtained by 
 dividing 60 by 7 = 8* miles, recorded as 9 miles. 
 
 When the anemometer cups are not moving at the time of observa- 
 tion, the wind will be recorded as calm, whether or not one or more 
 miles have been recorded during the last hour, and "cups not moving" 
 entered on margin of register sheet; if the cups are moving, a velocity 
 of 1 mile or more will be recorded. 
 
 27. Maximum velocity, how obtained from register. — The maximum 
 velocity of wind for any period will be obtained by considering the 
 number of spaces and fractions thereof between the mile marks in any 
 five minutes where the velocity is the greatest and multiplying the 
 result by twelve, the product will be the maximum velocity for that 
 period. 
 
 If the shortest space between two mile marks in the period covers 
 more than five minutes of time, then the time expiring in said space 
 will be the basis of the calculation. Example: If the shortest space 
 between two mile marks is thirteen minutes, then 60-^-13=4.6 miles 
 per hour for the maximum velocity, which will be recorded on Form 
 1001 as 5 miles. 
 
 28. Extreme velocity. — The extreme velocity will be ascertained each 
 day (from midnight to midnight) and will be computed from the mile 
 of wind recorded in the shortest time, thus: Find the two mile marks 
 nearest each other on the anemometer sheets from midnight to mid- 
 night. Measure accurately the time, in minutes and tenths, between 
 these marks (from beginning to beginning or from ending to ending), 
 using the engraved brass scale of minutes (referred to in paragraph 29). 
 Divide 60 by the time and the quotient will be the extreme velocity. 
 Example: Suppose the time on the scale is 1.6 minutes, then, 60-^1.6 = 
 37.5, which is the extreme velocity for the day, and will be recorded on 
 Form 1001 as 38. In this connection see paragraph 50. 
 
 29. Minute scales. — To secure greater accuracy in the calculation of 
 wind velocities from anemometer records, especially " extreme" veloc- 
 ities, some sort of scale, accurately graduated to minutes, should be 
 used in measuring the time between mile marks. Such minute scales 
 engraved in brass are now furnished for station use. 
 
 30. Maximum and extreme velocities entered on wind sheets. — The 
 " maximum" wind velocity (in any five minutes) occurring in each twelve 
 hours between the hours of observation at 8 and 8, and the "extreme" 
 velocity (1 mile in the shortest time) occurring between the hours of 
 midnight and midnight, will be entered in ink on Forms jSTo. 1015 and 
 No. 1017 immediately under or over these velocities as recorded by the 
 self-register. Care will be taken not to obliterate any record, and the 
 words maximum and extreme will be abbreviated thus : Max. 20, Ex. 30. 
 
 31. Current wind veloeity, how obtained from dial. — To obtain the cur- 
 rent velocity of the wind from the anemometer make two readings of 
 
13 
 
 the outer dial with an interval of five minutes between them. The 
 difference between these readings will be the distance, in miles and 
 tenths, traveled by the wind in that interval. This, multiplied by 12, 
 will give the indicated velocity in miles per hour. Example: Suppose 
 the index of the anemometer to be at 3.4 ou the outer dial when the 
 first reading is taken and at 4.1 five minutes after, the difference, 0.7 
 mile, is the distance traveled in that time ; and this, multiplied by 12, 
 gives a velocity of 8.4 miles per hour. Whole numbers only will be 
 used in expressing the velocity ; when the decimal is over five-tenths, 
 the whole number will be increased by one; when less than five-tenths, 
 it will be dropped; when just five-tenths, an odd unit's figure will be 
 increased by one, but an even number will not be changed ; for example, 
 such numbers as 13.5 will be changed to 14, the "3" being odd, while 
 12.5 will remain simply 12, the "2" being even. 
 
 32. The total movement by register for any period will be obtained by 
 counting the number of marks in the period. 
 
 33. Wind movement from noon to noon by dial. — To obtain the total 
 movement of the wind from noon to noon, subtract the reading of the 
 anemometer dial at 12 noon of the preceding day from the reading 
 taken at 12 noon of the current day, the difference will be the total 
 movement. When the reading of the anemometer is less than the read- 
 in g of the preceding day, 990 miles will be added to it, and the remain- 
 der, after subtracting the reading of the preceding day, will be the 
 total movement. Example: The dial reading of to-day is 91, and that 
 of yesterday was 950, hence we have 91 + 990 = 1081; 1081—950 = 131, 
 the total movement of the wind in miles from noon to noon. 
 
 • 34. Velocity of wind, estimated. — Whenever, through failure or other- 
 wise, instruments are not available for directly measuring the wind 
 velocity it will be estimated by reference to the following scale: 
 
 Kamo. 
 
 Miles per 
 hour. 
 
 Apparent effect. 
 
 Calm 
 
 
 1 to 2 
 3 to 5 
 6 to 14 
 15 to 24 
 25 to 39 
 40 to 59 
 60 to 79 
 80 or more. 
 
 
 Light 
 
 
 
 
 
 Moves small braoches of trees and blows up duBt. 
 Good sailing breeze and makes white caps. 
 
 
 
 
 Dangerous for sailing vessels. 
 Prostrates exposed trees and frail houses. 
 Prostrates everything. 
 
 
 
 
 35. Monthly maximum velocities. — In order to obtain the true max- 
 imum velocity of wind for the month, the anemometer sheets from mid- 
 night to 8 a. m. of the 1st, and from 8 p. m. to midnight of the last day 
 of the month will be examined in connection with the daily maximum 
 velocities since the last observation. 
 
 Example: The maximum wind velocity reported at 8 a. m. of the 1st 
 of June is 40 miles, occurring at 10 p. m. of May 31. The wind then 
 diminishes in force, but increases somewhat after midnight, attaining 
 
14 
 
 a velocity of 36 miles at 2:30 a. m. of June 1. This last velocity does 
 not appear among the daily "maximum velocities since last observa- 
 tion" during June, and should the wind reach a velocity of but 30 miles 
 on the subsequent days of- the month, the probabilities are that the 
 velocity of 36 miles on the 1st would be overlooked in recording the 
 maximum velocity for the month. 
 
 36. Dial readings. — A reading of the anemometer dial will be made 
 at noon on the first day of each month, and at noon each Monday dur- 
 ing the month, and will be recorded on the sheet just taken from the 
 register. Only actual dial readings will be recorded. 
 
 The accuracy of the anemometer record for each month may be veri- 
 fied at the end of the month as follows : Ascertain the total wind move- 
 ment by register from 12 noon of the 1st day of the month in question 
 to 12 noon of the 1st day of the succeeding month; add to this the dial 
 reading on the 1st day of the month being verified and divide the sum 
 by 990; the remainder should equal the dial reading on the 1st day of 
 the succeeding mouth. 
 
 Example. 
 
 Total movement, midnight to midnight , 3,283 
 
 12 hours preceding noon of the 1st 70 
 
 3,213 
 
 12 midnight to 12 noon of first of succeeding month 22 
 
 Dial reading on first day of month , 303 
 
 990)3, 538(3 
 2,970 
 
 Dial reading on first day of succeeding month 568 • 
 
 37. Anemometers changed. — "When the anemometer is changed a note 
 will be made on the lower margin of the anemometer record sheet, giv- 
 ing the date and hour of the change and the dial reading of both old 
 and new instruments. If changed at noon, both readings will be 
 recorded on the sheet just taken from the register. 
 
 38. Hourly wind movement. — This record for each day on Form Xo. 
 1022-Met'l must be completed on the day following that for which the 
 entries are made, or as soon thereafter as practicable, and the total for 
 each day compared with the total from midnight to midnight, for the 
 same period of time, entered on the face of the wind sheet. If the work 
 is correct, the totals from register and Form Xo. 1022-Met'l should 
 agree. 
 
 39. Miles and direction. — Enter on page 5, Form 1001-Met'l the total 
 number of miles and length of time, in hours and (nearest five) minutes, 
 midnight to midnight, of the wind from each direction, as shown on 
 the face of Forms 1017. A deviation of five minutes from a general 
 direction will hot be considered as changing that direction. Calin will 
 be recorded only when more than one hour has been consumed in 
 recording one mile. 
 
15 
 
 The time recorded as calm will be computed from "closing to closing," 
 or, from "opening to opening," of the circuit, whichever is shorter, a 
 movement of 1 mile being credited for each case. 
 
 A direction will be given whenever the movement is jnst 1 mile in 
 1 hour. 
 
 If the circuit remains closed on a single mile pin for more than 1 
 hour, the wind will be regarded as calm, but the movement will be 
 recorded as " OP 
 
 Each period of calm, as defined above, will be inclosed on Form 1017 
 in pencil brackets, and the sums of the periods and movements entered 
 in the appropriate columns on the margin of the form. 
 
 40. Hourly wind direction. — Enter on Form 1021-Met'l the prevailing 
 direction of the wind for each hour of the day, as recorded by the reg- 
 istering instruments. When the wind has blown an equal (or almost 
 equal) length of time from two or three directions, each will be recorded ; 
 but when the wind has been variable, rapidly shifting from one quarter 
 to another, the prevailing direction only will be entered, with an index 
 letter "v" to indicate "variable" immediately following the entry of 
 prevailing direction, thus " Sv." Whenever the hourly velocity is from 
 1 to 4 miles the direction entered from the register will be underscored. 
 When the wind movement is less than 1 mile per hour the entry will 
 be "0." 
 
 The prevailing direction for each hour, and for the day, will be the 
 direction or directions which occur most frequently in the respective 
 columns. The prevailing direction for the month will be taken from 
 the summary of Form No. 1001. 
 
 Form ~So. 1021 will be forwarded to the Chief of Weather Bureau 
 not later than the fifth day of the month succeeding that for which it is 
 the record; a letter-press copy being retained at the station. 
 
 41. Eainfall. — The total quantity of rain collected in the record- 
 ing float-gauge will be measured by stick at noon, after rain has 
 occurred, and the gauge emptied, except when rain is rapidly falling, in 
 which case it will be measured and emptied as soon as a pause or ces- 
 sation of the rain permits without serious or probable interference with 
 the record. Under such circumstances a note or mark will be made on 
 the record to indicate the time at which the gauge was emptied. 
 
 42. Total rainfalls measured by stick as above, together with rain- 
 falls of less than 0.05 inch, also measured by stick, will be entered on 
 
 Form 1017 in the space provided : "By stick ," which, in all cases, 
 
 refers to the stick measurements in the recording gauge and not in the 
 station gauge. 
 
 When the amounts by register and stick measurements for each day 
 do not agree (within 0.05 inch) a brief explanation of the cause of the 
 discrepancy should be noted upon the form upon which the disagree- 
 ment appears. 
 
16 
 
 43. In case of heavy or long-continued rainfall, which would probably 
 cause the gauge to overflow before the end of the twenty -four hours, it 
 should be emptied, if practicable, shortly before the overflow occurs. 
 The gauge reading or stick measurement, before being emptied, 
 together with the time, will be entered below the rainfall record on the 
 face of the form. 
 
 The hourly amounts of precipitation wifl be entered in red ink near 
 the middle of the hour period on the record sheet; for example, the 
 amount during the hour from 1 to 2 p. m. will be entered near the 1:30 
 p. m. line on the sheet. 
 
 Any information that will aid in determining the hourly amounts and 
 rates of rainfall, when imperfectly recorded, should be given. 
 
 44. When Form No. 1015-Met'l is used for rainfall record from the 
 recording float- gauge, the necessary changes will be made in ink in the 
 various headings. The sheets will be changed at noon only when rain- 
 fall has occur ed in the preceding twenty -four hours. The dates of no rain- 
 fall (12 noon to 12 noon) will, however, be entered in the blank space 
 of the lower right-hand corner of the sheet when changed. 
 
 45. Maximum rainfall. — On each day when precipitation occurs the 
 maximum amount of rain falling in five minutes, ten minutes, and in 
 one hour, together with the dates thereof, respectively, will be tab- 
 ulated in the spaces printed on the form, provided the precipitation has 
 amounted to at least 0.25 of an inch. The maximum for the month, 
 under the heads given above, will be underscored in red ink. 
 
 See also paragraphs 122 to 127 for additional instructions respecting 
 the tabulation of rainfall data. 
 
 46. Thermometric sunshine records. — The instructions following 
 relate, to the operation of the electrical sunshine recorder, which records 
 on the triple register sheet. 
 
 Full details of the electrical circuits when this recorder is made to 
 register, either alone or in connection with the float rain gauge, will 
 be found in Circular D, pp. 31 and 32. 
 
 47. Critical condition for registration. — The inclination of the 
 recorder will be adjusted at such an angle that the mercury column will 
 just close the electrical circuit during times when the disk of the sun 
 can just be faintly seen through the clouds. If the cloudiness is such 
 that the observer can not clearly distinguish the sun's disk, then the 
 mercury should not rise high enough to close the circuit. Several 
 trials on successive days may be necessary to secure the best adjust- 
 ment. In altering the inclination of the recorder it is best to first make 
 a chalk or pencil mark across the edges of the hinge joint of the sup- 
 port before it is loosened. Any change made in the inclination of the 
 tube is then clearly shown by the amount the lines on the two parts of 
 the hinge separate from each other. If it is desired to make a subse- 
 quent adjustment the first lines are easily erased and a new mark 
 made. 
 
17 
 
 48. When both sunshine and rain are recorded ou the same sheet, 
 the portion representing rain will be clearly marked by brackets, etc., 
 and such footnotes added as may be necessary to completely identify 
 the records, in case there is likely to be uncertainty. 
 
 49. Form 1070. — The data obtained from the automatic electrical reg- 
 istration of sunshine will be tabulated on Form 1070- Met'l, in accord- 
 ance with the instructions in paragraphs 84 to 95. 
 
 50. Caution against errors. — In older forms of triple registers with 
 five-minute contacts the cylinders, not being perfectly balanced, and 
 being sometimes held a few seconds by the wind direction points, 
 revolve in a slightly irregular manner, the effect of which, during high 
 wind velocities, is to cause some of the mile marks to be abnormally 
 close together, indicating thereby a false extreme wind velocity. 
 These false extreme velocities are likely to be isolated and widely dif- 
 ferent from the velocities recorded just before and after, whereas the 
 true extreme velocities will differ but little from the associated veloci- 
 ties and will occur iu a group of mile marks all comparatively close 
 together. 
 
 Observers will bear this matter in mind and will not report extreme 
 velocities which, in their judgment, are the result of imperfect action of 
 the instrument. A marginal note will be made in each case of a false 
 record. 
 
 RECORDS FROM BAROGRAPHS AND THERMOGRAPHS. 
 
 51. Sheets. — Barograph and thermograph sheets will each - be clearly 
 marked on the face of the sheet with the name of station and date, each 
 day's record being dated as near the noon line for that day as practi- 
 cable. 
 
 52. The sheets for the iveelcly instruments will be changed at about 
 noon, Monday. New sheets will not be used on the beginning of a 
 month, except, of course, it be Monday as well. 
 
 53. When an instrument is first put in operation the trace on the 
 sheet should start at the proper date and hour, even if near the end of 
 the sheet. 
 
 54. At stations supplied with instruments the cylinders of which 
 make two revolutions per week, the sheets will be changed on Mon- 
 day a. m., in the usual manner. On Thursday, at about 9 p. m., lift 
 the pen and turn the cylinder around to the left until the pen stands 
 at the corresponding hour a. m. of the preceding Monday, at which 
 point the record for the last half of the week will be started. Little 
 or no confusion should result from this double record if care is observed 
 in dating the lines and curves. The time lines of the sheet represent- 
 ing the noon hours will be properly dated before the sheet is put on the 
 instrument, and the temperature curves will also be dated near the 
 point of starting and ending, as shown in diagram, Fig. 1. 
 
 6581 2 
 
18 
 
 55. The lower edge of the sheet should rest closely against the flange 
 at the bottom of the cylinder, and the pen be adjusted to the proper 
 temperature, or pressure, as the case may be. The barograph should 
 be made to agree as nearly as possible with the mercurial barometer 
 when the latter is corrected for temperature and instrumental error. 
 
 56. Thermograph and barograph set for time, temperature, and pres- 
 sure. — After the record sheet is on the cylinder, the pen of the thermo- 
 graph may be set to indicate the true temperature by adjusting the 
 small screw over the bulb of the thermometer. This screw is turned 
 by the aid of the small end of thekey used is winding the clock move- 
 ment of the instrument. 
 
 57. The barograph is set to the true pressure by turning a screw 
 under the base of the instrument. The instrument must be held up in 
 one hand for this purpose and the screw turned by the clock key. 
 
 58. In setting, it is best to tap or jostle the instrument somewhat 
 in order to cause the various parts and levers to settle into their normal 
 
 ITig. 1. — Weekly thermogram on semiweekly record sheet. 
 
 positions; otherwise the pen, which may seem to be correctly set for a 
 time, is likely to change its position without apparent cause. In any 
 case, however, it is scarcely possible to set the pens exactly to the true 
 temperature or pressure, and slight corrections are almost always 
 required. 
 
 59. The barograph and thermograph -records are set to correct 
 time by forcibly turning the cylinder on its axis either forward or back 
 so that the pen indicates the exact time. It is not necessary to twist 
 the sheet around on the cylinder nor to lift the latter partly upon its 
 axis. 
 
 60. Lost motion. — As explained in paragraph 22, it is necessary to con- 
 sider the looseness in register cylinders when setting the record to correct 
 time. Touch the flange or edge of the cylinder lightly with the finger tip, 
 and draw it off in a manner that will tend gently to revolve the cylin- 
 der in a direction opposite to that in which it revolves. Repeat the 
 operation once or twice. If the pen does not then indicate the correct 
 time, the cylinder must be shifted until a satisfactory setting is 
 obtained. 
 
19 
 
 61. At the time of adjusting the barograph or thermograph pen, or 
 when changing the record sheet, a reading of the station barometer (or 
 dry thermometer) will be made and entered on Form 1026, together 
 with the correction (in red ink) necessary to reduce the reading of the 
 register to the standard. The corrections to be used for hours between 
 this reading and the regular 8 o'clock, or other readings before and 
 after, will be determined from the correction card by use of a pin, or 
 pins, as explained in paragraph 69. 
 
 62. Thermograph time error. — At the time of taking the 8 a. m. 
 observation the observer will carefully touch with a lead pencil the 
 lever projecting from the thermograph bulb so as to cause the pen to 
 make a short vertical mark on the sheet. A proper memorandum note 
 must be made as to the exact time and date the mark was made, and 
 when the sheet is removed the appropriate hour and minute will be 
 entered in black ink at the proper place on the sheet. If the mark is 
 made at precisely 8 a. m. (or within a minute or so), no note need be 
 made on the sheet. 
 
 63. Barograph time error. — The actual time error of barograph 
 clocks will be noted in like manner at 12 noon each day, by delicately 
 touching the pen arm about 2 inches from the pen. 
 
 In producing these marks great care must be exercised not to strain 
 the lever mechanism in any way. The weight of an ordinary lead pencil 
 is amply sufficient to make the mark, which should not be more than 
 one-eighth of an inch in length. 
 
 61. When the pressure or temperature at any particular station is such 
 that the record might pass off the edge of the sheet, or not be at all 
 included in the rulings, observers will change the numbering of the 
 lines by some convenient whole number aud adjust the pen of the instru- 
 ment accordingly. 
 
 65. Clocks. — Every effort should be made to properly regulate the 
 clocks to correctly keep seventy- fifth meridian time, winding them once 
 a week, or oftener, if necessary. The instruments should be inspected 
 each day, by, the observer in charge, and properly adjusted by him, 
 when necessary. Whenever they are adjusted a marginal note, stat- 
 ing the fact, will be connected with the proper hour. 
 
 66. Pens.— Pens should be kept neat and clean. Only the standard 
 thermographic ink should be used. Care must be observed, however, 
 in cleaning a pen not to bend or deform the points and render it unserv- 
 iceable. 
 
 67. Corrections. — Owing to imperfections in barographs and ther- 
 mographs, more or less frequent comparisons should be made with 
 standard instruments. The difference between the indications of the 
 two constitutes a correction by which the automatic records are reduced 
 to standard values. Such corrections apply not only to the hours _at 
 which the comparisons are made, but also affect values for intermediate .■ 
 
20 
 
 hours, and, as the correction may change from time to time, the deter- 
 mination of the most probable correction for any particular hour is 
 greatly facilitated by the use of the device known as the "Thermograph 
 correction card." 
 68. Correction card, how used. — Ascertain the difference between the 
 
 thermograph reading and the dry- 
 bulb thermometer reading at any 
 8 o'clock observation under con- 
 sideration; then set the rubber 
 band on the card in a notch at the 
 left-hand edge corresponding to 
 this difference. 
 
 If this difference, or correction, 
 must be added to the thermo- 
 graph reading to make it agree 
 with the dry-bulb reading, then 
 the band must be set above the 
 middle line, or, if the difference 
 must be subtracted, set the band 
 below. 
 
 In a similar manner set the 
 band in a notch at the right-hand 
 edge of the card corresponding to 
 the difference between the ther- 
 mograph reading and the dry- 
 bulb thermometer reading at the 
 next 8 o'clock observation. 
 
 The thermograph correction at 
 any hour between the 8 o'clock 
 observations is the distance above 
 
 I /J 
 
 
 
 
 
 
 
 
 
 
 
 fS J 
 
 [ >4 
 
 
 
 
 
 
 
 
 
 
 
 M- J 
 
 [ /3 
 
 
 
 
 
 
 
 
 
 
 
 13 J 
 
 \/2 
 
 
 
 
 
 
 
 
 
 
 
 12 J 
 
 [ // 
 
 
 
 
 
 
 
 
 
 
 
 /./ J 
 
 [ /O 
 
 
 
 
 
 
 
 
 
 
 
 10 J 
 
 
 
 
 
 
 
 
 
 
 
 
 9 j 
 
 I 3 
 
 
 
 
 
 
 
 
 
 
 
 a J 
 
 L ? 
 
 
 
 
 
 
 
 
 
 
 
 ? J 
 
 L 6 
 
 
 
 
 
 
 
 
 
 
 
 6 J 
 
 I 5 
 
 
 
 
 
 
 
 
 
 
 
 5 J 
 
 L 4 
 
 
 
 
 / 
 
 / 
 
 
 
 
 
 
 *■« J 
 
 I 3 
 
 
 
 
 / 
 
 
 
 
 f 
 
 s 
 
 / 
 
 3 J 
 
 L 2 
 
 
 
 
 
 
 
 / 
 
 
 
 
 8 J 
 
 1 J^ 
 
 
 
 
 
 
 \ 
 
 // 
 
 
 
 
 / J 
 
 w ' 
 
 1 It 
 
 ? 7 
 
 f 7 
 
 7 
 
 f ' 
 
 > 
 
 } 
 
 r 
 
 
 ? " 
 
 7 t5s 
 
 IV o 
 
 I / 
 
 
 
 
 
 
 
 
 
 
 
 / J 
 
 I ?< 
 
 
 
 
 
 
 
 
 
 
 
 2 J 
 
 I 3 
 
 
 
 
 
 
 
 
 
 
 
 J J 
 
 L 4 
 
 
 
 
 
 
 
 
 
 
 
 4 J 
 
 ? 5 
 
 
 
 
 
 
 
 
 
 
 
 S J 
 
 { es 
 
 
 
 
 
 
 
 
 
 
 
 (S ) 
 
 I 7 
 
 
 
 
 
 
 
 
 
 
 
 p J 
 
 L & 
 
 
 
 
 
 
 
 
 
 
 
 s \ 
 
 \ 9 
 
 
 
 
 
 
 
 
 
 
 
 9 J 
 
 I ro 
 
 
 
 
 
 
 
 
 
 
 
 fQ J 
 
 L rt 
 
 
 
 
 
 
 
 
 
 
 
 // J 
 
 1/2 
 
 
 
 
 
 
 
 
 
 
 
 72 J 
 
 \/3 
 
 
 
 
 
 
 
 
 
 
 
 /3 J 
 
 \/4 
 
 
 
 
 
 
 
 
 
 
 
 m\ 
 
 [ /s 
 
 
 
 
 
 
 
 
 
 
 
 /S } 
 
 [ 
 
 
 
 
 
 
 
 
 
 
 
 
 3?IQ. 2. — Thermograph correction card. 
 
 or below the middle line of the point at which the band crosses that 
 particular hour line. 
 
 Example. 
 
 Difference at first 8 o'clock observation: +2 (band above middle line). 
 Difference at next 8 o'clock observation : — 3 (band below middle line). 
 
 Hourly correction taken to the nearest unit. 
 
 9 10 11 12 1 2 3 4 5 6 7 
 + 2 + 1 + 1 000-1-1-2-2-3 
 
 This card will also be used in a similar manner tor correcting baro- 
 graph readings. 
 
 60. Eye readings of the thermometer and barometer at exact hours, 
 as provided for in paragraph 67, should be used to check and correct the 
 corresponding recording instruments. If the correction at 12 o'clock, 
 
21 
 
 or example, was + 3, and at 3 o'clock + 1, then if pins be stuck in 
 the card at these points the rubber band may be deflected in the man- 
 ner shown in the figure, and a complete series of corrections for the 
 twelve-hour period from 8 to 8 determined. 
 
 70. Hourly readings. — The hourly readings of the thermograph and 
 barograph, after being corrected for instrumental error in accordance 
 with the above instructions, will be entered in black ink on Form 
 1026-Met'l, in whole numbers for temperatures and two decimal places 
 for pressures. At 8 a. m. and 8 p. m., and at all other hours at which 
 eye readings are made, the black ink figures will be the readings of 
 the standard instruments (corrected for temperature and instrumental 
 error in case of barometric readings), and in the same hour column will 
 be icritten, in red ink, with its appropriate sign, the correction for the 
 self -registering instrument. 
 
 71. Daily range. — The data entered in the columns of Form 1026-Met'l 
 (hourly thermograph readings) headed "Max.," "Min.," and "Eange," 
 respectively, will be taken from the observed readings of the station maxi- 
 mum and minimum thermometers, and will be an exact transcript of the 
 first three columns on page 6, Form 1001-Met'l. 
 
 72. Enter in column headed " Range of thermograph" the daily range 
 of temperature as shown by the corrected thermograph readings. 
 
 73. Base number. — With a view to reducing the labor of preparing 
 Form 1026-Met'l (hourly barograph readings), observers will enter in 
 the body of said form the fractional or decimal part of the readings 
 only; the integer which is constant will be called the base number, and 
 will be entered once for all on the upper left-hand margin of the form, 
 thus, 29. + inches, or 26. + inches, as the case may be, according to the 
 elevation of the station. 
 
 Thus, if the base number is 29 inches, 29.06 will be entered .06; 29.90, 
 .90; 30.10, 1.10. 
 
 Readings below the base number will be entered as above, except 
 that they will be preceded by the minus sign ; thus, if the base num- 
 ber is 29., the reading 28.60 will be entered — .40. As a rule the base 
 number will be low enough to probably preclude the occurrence of 
 any considerable number of readings involving the entry of minus 
 quantities. 
 
 74. Footings. — The sums and means will be determined from the 
 data entered in accordance with the foregoing instructions. The ther- 
 mograph means and averages being recorded to tenths, and barograph 
 means and averages to thousandths. 
 
 75. Form 1026-Met'l, together with the corresponding trace sheets 
 (which must include the trace for the whole of the last day of the 
 month), will be forwarded, in an envelope marked "Records," to the 
 Chief of the Weather Bureau not later than the 12th of the month 
 succeeding that for which it is the record. 
 
22 
 
 Automatic records of sunshine. 
 
 16, The sensitized cliarts for the photographic recorder will be pre- 
 pared by trimming off across the bottom of the sheet at the line just 
 beneath the name of the month for which the sheet is to be the record. 
 The top will be trimmed to the dotted line and the sides and center cut 
 along the -.-.-.-. line. The two parts of the sheet (that is, the 
 part for the forenoon and the part for the afternoon sunshine, respec- 
 tively) will then be slipped into their appropriate compartments of the 
 Instrument, taking care that the chart for the forenoon record will face 
 toward the east and that for the afternoon record face toward the west 
 and that the sheet is not upside down. 
 
 77. These operations are most safely performed in a darkened room 
 or, preferably, at nighttime by artificial light. The charts should, 
 therefore, be carefully prepared and placed in the recorder after sunset 
 of the last day of the month (except when it is desired to commence a 
 record other than on the first of a month), the slides of the recorder 
 set to their proper places to register for the first day of the month, and 
 the instrument replaced on its support on the roof of the office building 
 or other point selected for the exposure. 
 
 78. While the blank sensitized charts may be used during an entire 
 month, it has been found that much better records are obtained if 
 sheets are changed on the 1st and 15th of each month. Charts will, 
 therefore, be changed twice a month at such stations as receive two 
 sets per month. 
 
 79. Great care must be taken before the prepared charts are used not 
 to expose them to daylight, as they will thus be rendered worthless for 
 the purpose for which they are intended. The metal cylinder should, 
 therefore, always be removed to the office room before opening. 
 
 80. Each night, after sunset, the slides will be moved downward one 
 notch, in order that the recorder may be in readiness for the next day's 
 record. 
 
 81. After sunset of the last day (or 15th) of the month, the cylinder 
 will be removed to the office, the charts taken therefrom, and the record 
 rendered permanent in accordance with the instructions contained in 
 the next paragraph. New sensitized charts will then be inserted and 
 the instrument exposed. 
 
 82. The records obtained are rendered permanent when taken from 
 the instrument by simply washing the charts in water and afterwards 
 drying them between sheets of blotting paper in a letterpress. The 
 charts should be immersed in running water, if possible, for a half 
 hour, or more, or until the surface of the paper becomes nearly white 
 and the sunshine record is brought out in a bright, blue color. 
 
 PREPARATION OF FORMS 1065 AND 1070-MET'L. 
 
 83. The photographic charts containing the month's record of sun- 
 shine will be neatly pasted in the appropriate spaces on Form 1065, 
 which will be filled out with proper dates and headings. 
 
'23 
 
 The meteorological data compiled from these charts and also from 
 the electrical record on Form 1017 will be tabulated on Form 1070. 
 
 84. The actual time sunshine was recorded during each hour will be 
 entered to the nearest tenth of an hour in tlie appropriate columns 
 under heading " Sunshine recorded during hours ending" (5 a. m. to 8 
 p. in., local time). 
 
 85. The photographic record of sunshine obtained on the sensitized 
 charts is, of course, recorded on local time. When the record is obtained 
 from an electrical instrument recording on Form 1017-Met'l, it should 
 be remembered that the record is made on seventy-fifth meridian time, 
 and in tabulating the record on this form (No. 1070), the difference 
 between local time and seventy-fifth meridian time must be considered. 
 
 For example: If the local time of the station is twenty minutes faster 
 than seventy-fifth meridian time, in reading off the sunshine record, 
 the hour lines ruled on Form 1017 must be considered as having been 
 moved back twenty minutes, so that the 6 a. in. line will fall at 5:40 a. 
 m. and the noon line 11 :40 a. m., etc. Or, if the local time is one hour 
 and thirty- five minutes slower than seventy-fifth meridian time, then 
 before reading off the sunshine record the observer must consider the 
 hour lines ruled on Form 1017 to have been moved ahead one hour and 
 thirty -five minutes; 6 a. m. would then fall on the 7:35 a. m. line and 
 noon would fall on the 1 : 35 p. m. line, etc. The sunshine record for 
 hours ending 5 a. m. to 8. p. m. would then be obtained with reference 
 to these adjusted hour lines. 
 
 8G. The "Character ot sunrise and sunset " will be recorded as clear 
 or cloudy, depending upon whether the horizon was clear or obscured 
 by clouds at the time of sunrise and sunset, and the word "clear" or 
 "cloudy," as the case may be, will also be recorded on Form 1017 in 
 pencil at the time of sunrise and sunset, respectively. 
 
 87. It is not intended that observers shall go on duty at unreason- 
 ably early hours in order that the character of sunrise may be deter- 
 mined; but it is believed that without much inconvenience sufficiently 
 accurate data can be obtained by noticing the character of sunshine 
 immediately upon rising and by inquiry of persons who may have 
 occasion to be up at time of sunrise. 
 
 88. Twilight correction. — When the sun is just above the horizon, 
 either morning or evening, the intensity of its action on both the 
 thermometric and photographic recorders is greatly diminished, even 
 with clear skies, so that a portion of early morning and late afternoon 
 sunshine will not generally be recorded, and allowance therefor must 
 be made in order to ascertain more accurately the actual amount of 
 sunshine. For convenience this allowance will be called the " Twilight 
 correction." In the forenoon it will be the difference between the 
 time of sunrise for the latitude of the station (as shown by table of 
 Sunrise and Sunset, Table I), and the local time at which the sunshine 
 record commenced, provided the sun was not obscured by clouds or 
 
'24 
 
 thick haze during the period. The afternoon twilight correction simi- 
 larly will he the difference between the actual time of sunset and the 
 time the record of sunshine stops. These corrections will be appor- 
 tioned between the appropriate hours of early morning and late after- 
 noon and entered in the upper left hand part of the space in red ink, 
 on Form 1070, as follows : 
 
 Suppose Table I gives sunrise at 5.87 hours and the record of sunshine begins at 
 7.2 hours ; also, that the ' ' Character of sunrise " was ' ' clear" ; then the total forenoon 
 twilight correction will be 7.2— 5.87=1.33 hours. Of this 0.13 (see paragraph 95) 
 will be entered in red ink in the column headed 6; 1.0 will be entered in red ink in 
 column headed 7; and finally 0.2 will be entered in red ink in column headed 8. This 
 latter column will also contain the entry 0.8 in black ink, that being the amount of 
 sunshine recorded during the hour in question. The twilight correction for after- 
 noon sunshine will be apportioned in a similar manner. 
 
 89. If the character of sunrise or sunset is cloudy, the twilight cor- 
 rection will then be regarded as zero, but when the observer knows 
 that cloudiness has prevailed but part of the time he will employ such 
 a value of twilight correction as will represent, in his judgment, the 
 actual sunshine not recorded. 
 
 90. The column headed " Twilight correction " will contain the sum 
 of the forenoon and afternoon corrections, expressed to the nearest 
 tenth of an hour. 
 
 91. The column headed " Total," under " Hours of sunshine," will 
 contain the daily sums (expressed to the nearest tenth of an hour) of all 
 the hourly entries for each day, including the red ink twilight correc- 
 tions. 
 
 92. The hours of possible sunshine will be taken from Table II, 
 "Approximate hours of possible sunshine," furnished also in card 
 form. 
 
 93. " The percentage of possible " will be obtained by dividing the 
 total sunshine by the possible sunshine for the same day, and will be 
 recorded to the nearest whole per cent. 
 
 The monthly percentage of possible sunshine, by hours, will be 
 obtained by dividing the "sum" in the same vertical column by the 
 number of hours of possible sunshine for the entire month for that par- 
 ticular hour of the day. The divisor will, of course, equal the number 
 of days in the month, except for those hours that end shortly after the 
 time of sunrise and sunset, which hours are entitled to only a fraction 
 of an hour of sunshine each day. 
 
 94. The divisor to be used in such a case is the sum for the whole month 
 of these fractional portions which change from day to day with the time 
 of sunrise. Table III (also furnished in card form) contains these sums 
 or divisors for different latitudes and for each month, and will be used 
 by observers who will take therefrom the proper divisors to be used in 
 compiling Form 1070. 
 
 The sums and means will be recorded to the same number of decimal 
 places as the data from which they are obtained. 
 
25 
 
 95. Accumulation of errors avoided. — The first portion of morning 
 and the last portion of afternoon sunshine are apportioned and recorded 
 on Form 1070 as twilight corrections. If these entries are recorded to 
 the nearest tenth of an hour only, the error made by neglecting a few 
 hundredths each day accumulates and causes a serious discordance 
 both between the daily "total" and "possible," and more particularly 
 between the divisors taken from Table III, and the first and last " sums" 
 in the columns headed "Hours ending.'' 
 
 To prevent such discordance the first and last portions of twilight 
 correction for each day will be recorded to the nearest hundreth of an 
 hour; provided the sun, when at the horizon, was not obscured by 
 clouds. All other entries will be to the nearest tenth of an hour. 
 
 AUTOMATIC RECORDS OF PRECIPITATION. 
 
 96. Beginning and ending of precipitation. — -The precise time of begin- 
 ning and ending of precipitation can not be obtained from automatic 
 records with uniform accuracy under all conditions. The beginning 
 and ending of sudden and heavy showers may be shown with very 
 considerable accurracy, but the record of very gentle rain and snow 
 falls, however, may begin an hour or more after the very first precipi- 
 tation. 
 
 Observers will, therefore, as far as possible, make eye observations 
 from day to day of the time of beginning and ending of the several 
 periods of precipitation that may occur. 
 
 97. Such eye observations will be recorded on the automatic record 
 sheets (Forms 1017 (1015) and 1028) by direct and reversed check 
 marks, thus, (•) (V), accompanied by the letters B and E, respect- 
 ively; said check marks being placed alongside the record at the points 
 corresponding in time on the sheet to the observed times of beginning 
 and ending of precipitation. Whenever the time of beginning or end- 
 ing is doubtful the entry will be accompanied by a query mark ( !). 
 Any information that will aid in determining the hourly amounts and 
 rates of rainfall, when imperfectly recorded, should be given. 
 
 98. The characters B. D. N. or E. D. N. will be used to denote the 
 beginning and ending of precipitation during the night. 
 
 99. Records from recording float gauge. — See paragraphs 41 to 45 
 
 100. Records from weighing gauge. — The clock movement of the reg- 
 ister will be wound at noon each day, and, if necessary, the clock set 
 and regulated to correctly keep seventy-fifth meridian time. 
 
 Sheets will be changed at noon under the following provisions: 
 
 101. A new sheet being upon the register, the observer will, by actual 
 trial and setting, if necessary, be assured that the weighing mechan- 
 isms are in equilibrium, as explained in paragraph 45, Circular E, 
 Inst. Room, the pen during this operation being lifted from the sheet. 
 Equilibrium being established, the pen point will be adjusted to follow 
 the top line of the sheet, the index pointing to zero on the notched 
 wheel. (See paragraphs 24 and 25, Circular E, Inst. Booin.) 
 
26 
 
 102. If precipitation does not occur in the ensuing twenty-four hours 
 retain the sheet upon the cylinder and at noon set the pen at the tenth 
 line, marked .10, on the form. This adjustment of the pen is to be 
 effected by lifting the crescent-shaped nut from the thread of the screw 
 and shifting the sleeve and nut the required distance, being careful 
 not to move the pen laterally in its own bearings, and to enter the nut 
 into the left-hand thread, that is, the one, that will carry the pen toward 
 the bottom of the sheet. 
 
 103. If twenty-four hours again pass without rainfall, the pen will be 
 set at the .20 line on tbe sheet, and so on. 
 
 104. At noon, ending the sixth day without rainfall, the pen will have 
 traced the bottom line of the sheet, which will then be removed and a 
 new sheet started, with the pen set at the top line. The several lines 
 traced by the pen upon the sheet just removed will be separately and 
 plainly marked, each, with the day of the month of which it is the record 
 of the absence of precipitation, the sheet being further dated and 
 marked as called for by the blanks of the form. 
 
 105. At noon, when precipitation has occurred, the pen will be lifted 
 from the record sheet, making due note' of the reading of the sheet and 
 notched wheel ; the gauge will be emptied and readjusted and the sheet 
 changed, except as specified in paragraph 106. The sheet removed 
 will be dated and the actual amount of precipitation entered in the 
 blank space on the form. Whenever the precipitation is in the form 
 of snow, this circumstance will be appropriately noted on the face of 
 the record. 
 
 106. When rain or snow, already partly recorded, is falling heavily at 
 noon, the sheet will be allowed to run another day without resetting the 
 pen or emptying the gauge. 
 
 107. When it is raining lightly, or upon rainy, wet days, when precipi- 
 tation is probable at any time, the sheet may be changed at noon, but 
 the gauge need not be emptied unless it contains a large quantity of 
 water, in which case there is danger of losing record by the weighing 
 limit of the gauge being surpassed. The limit is about 3 inches of 
 rain. 
 
 The gauge m such an emergency may be emptied at any time, and, if 
 possible, readjusted during a cessation of rainfall, always entering an 
 asterisk and explanatory footnote at the break in the continuity of the 
 record necessarily occasioned. 
 
 108. When, for any reason, the gauge is emptied at any hour other than 
 noon, first make note of the reading of the notched wheel of the reg- 
 ister. Lift the pen from the sheet without moving it laterally, and re- 
 adjust the gauge'. The sheet will not be changed. The pen will be set as 
 follows: (a) If rain be not falling, turn the notched wheel to the same 
 graduation as before, and, by shifting the sleeve, set the pen on the line 
 previously traced; or (b) if the gauge was emptied during the rain, a 
 small portion of the record may be lost, and the pen must then be set 
 
27 
 
 so as to trace the most probable continuation of the preceding record. 
 Explanatory footnotes will be entered in all such cases. 
 
 109. When tlie guage is about to be emptied after rainfall, the ob- 
 server will ascertain, by pressing upon tbe balance with the finger, 
 whether it is in equilibrium or not. 
 
 110. Scale readings. — When the weighing gauge is in equilibrium, 
 the total quantity of water in the receptacle is accurately indicated by 
 the scale readings (see paragraphs 31 and 35, Circular E). Due 
 account, however, must be taken of the scale reading when the gauge 
 is empty. This latter reading may be made zero (0) (and need not then 
 be considered) by adjusting the counterpoise, as described in para- 
 graph 26, Circular E. 
 
 If the gauge recorded properly throughout a period of precipitation, 
 the scale reading is a correct measure of the total rainfall, even though 
 some of the water may escape by evaporation. 
 
 111. If the electrical actions fail to bring about equilibrium, the 
 observer may himself set the sliding weight by hand, so that the gauge 
 is in almost perfect equilibrium. The scale reading then indicates the 
 total rainfall. 
 
 112. Stick measurements. — At noon, after each precipitation, the 
 observer will note that the total precipitation indicated by the record 
 sheet agrees with the scale reading of the gauge, and, if the observer is 
 in any doubt about the matter, the water in the weighing gauge will 
 be carefully poured into and measured in the measuring tube of the 
 station gauge. Such stick measurements or such gauge readings will 
 be entered on the record sheet. 
 
 113. At noon each day, after the absence of rainfall, the observer will 
 note whether or not the notched wheel of the register stands at zero as 
 set the day before, and he will take such action as may be necessary 
 both to readjust the gauge and to ascertain and eliminate the cause of 
 the disturbance. The wind is often the cause of slight disturbances 
 of a few notches. 
 
 114. If the accidental disturbance of the equilibrium is sufficient to 
 show upon the sheet, proper footnote will be made in explanation. 
 
 115. Whenever the equilibrium is accidentally disturbed sufficient to 
 show upon the sheet, the gauge will be readjusted as soon as the fact 
 is discovered, setting the pen at the proper line and the notched wheel 
 at zero. 
 
 116. Before leaving the gauge after readjustment secure the iron cover 
 firmly to the base by the hooks provided and latch the door. 
 
 117. A thorough test of the condition of the gauge, batteries, etc., will 
 be made at least once each week. During the test the pen will be lifted 
 from the sheet. Dust and foreign matter that may lodge on the bal- 
 ance, especially the beam traversed by the sliding weight, should be 
 removed with a rag moistened with a little oil. Slide the carriage back 
 and forth to see that it is free. 
 
28 
 
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 118. Explanation of rec- 
 ordsheet. — A singlesheet 
 is expected to coutain 
 the record for twenty- 
 four hours. The pen is 
 set at the top (at the left) 
 andonthenoon line when 
 the sheet is changed. If 
 rain does not fall in the 
 first twelve hours, the 
 pen will trace a line over 
 the top line of the sheet. 
 The twelve hours follow- 
 ing the pen will, in case 
 there is still no rain, re- 
 trace the same line. The 
 record will always show, 
 therefore, -whether the 
 rain occurred in the first 
 or second twelve -hour 
 period. If in the first, 
 an ink line will extend 
 only part way across the 
 sheet; if in the second, 
 there will be a continu- 
 ous ink line clear across 
 the sheet at the top, and 
 the rain record will ex- 
 tend transversely across 
 the sheet. 
 
 119. Fig. 3 shows a 
 sample record. Two pe- 
 riods of rainfall are re- 
 corded. Rain began at 
 2:38 p. m. (note the ab- 
 sence of ink line at top 
 of sheet after 2:38). 
 Prom 2:38 to 2:57 the 
 line inclines sharply 
 across the sheet. This 
 indicates a rather rapid 
 rate of precipitation. 
 After 2 : 57 the rain grad- 
 ually ceases, stopping 
 entirely by 3:30 p. m. 
 The amount of rain up to 
 
29 
 
 this time is a little over : 14 inch. Eain began again at 3 minutes past 
 10 p. m. The rate at first is less rapid in this case; it increases later, 
 however, raining steadily as shown by the straightness of the line, until 
 11 : 20 p. in., continuing thereafter at a slower and less regular rate until 
 2 : 25 a. m., at which time rainfall ceased. The total rainfall is seen to be 
 0.50 (from top to bottom), plus 0.42 (from bottom upward), equals 0.92, 
 that is, the total rainfall is ninety-two hundredths of an inch. 
 
 120. Rate of rainfall. — The rate of rainfall is shown by the inclination 
 of the trace to the time lines of the sheet. One way of ascertaining the 
 rate at any portion of the record is to prolong the trace by a pencil line 
 and note the number of spaces crossed by the line from one hour line 
 to the next. Example: To find the rate at the portion of the record 
 marked a, prolong the trace as shown by the broken line. We find that 
 this line crosses, in all, eleven spaces of the longitudinal rulings in the 
 hour between 1 and 2; that is, the rate is 0.11 inch per hour. 
 
 121. A much better way of ascertaining rates is by the use of a rectan- 
 gular plate of glass or transparent celluloid, having smooth edges and 
 a few inclined lines scratched or engraved upon one face. This plate 
 is laid over the record and one of its lines superposed exactly over the 
 portion of trace where the rate is desired. Holding the glass in posi- 
 tion, a straightedge is placed against one edge of the plate, which we 
 now slide along the edge as a guide, so that the engraved line intersects, 
 let us say, the top line of the sheet exactly at one of the hour lines. 
 Following the engraved line across the sheet, with the eye, we note the 
 number of longitudinal rulings crossed in one hour, or some convenient 
 fraction thereof, as one-half hour. 
 
 PREPARATION OF FORM 1040; HOURLY PRECIPITATION READINGS. 
 
 122. The records of precipitation obtained from automatic instru- 
 ments will be tabulated as fully as x>ossible on Form 1040— "Hourly 
 precipitation readings." 
 
 123. The stick measurements of total rainfall made at 8 a. m. and 8 
 p. m., from the, regular station gauge, will be entered in red ink in the 
 columns headed " Total standard." 
 
 124. All data obtained from snow or mixed snow or rain will be 
 entered in red ink. Data from mixed snow and rain will be marked 
 with an x . 
 
 125. The time of beginning and ending of precipitation will be indi- 
 cated on Form 1040 by the use of direct and reverse check marks 
 (V), (V ) placed within the hour space and on the top line for the 
 date in question. A time like 9:15 a. in., for example, will be indi- 
 cated by placing the check mark in the column headed "10 a. m.," and 
 at a point one fourth the distance from the left-hand side of the column. 
 Other fractional parts of hours will be indicated in like manner. The 
 check marks will be in red ink for eye readings, which are preferred, 
 and in black ink if the readings are from the automatic record. (See 
 paragraph 96.) 
 
30 
 
 126. When precipitation occurs during the night and the time limits 
 are not known, the total amount only will be entered in tbe column 
 headed, " Total register" 8 a. m., and the letters B. and E. D. N. will 
 be placed in the upper part of the space headed "0 to 1." 
 
 127. Similarly, in cases of precipitation only partly recorded, the 
 hourly amounts for the period during which the record was defective 
 will be estimated if sufficient data is available, otherwise they will be 
 omitted, but the totals "by stick" for preceding 12 hours will in every 
 case be entered in the proper 8 a. m. or 8. p. in. column. 
 
 128. Maximum rates of rainfall as provided for in paragraph 45 will 
 also be recorded in the columns headed " Maximum fall in." 
 
 129. Snowfall. — The measurement of precipitation in the form of 
 snow is attended with grave uncertainties due to the action of the wind 
 in drifting the snow and preventing it from entering gauges or blowing 
 out portions of snow that have entered. The best automatic gauges act 
 by weighing the snow fall collected, but in all forms thus far devised the 
 mechanisms, being of necessity somewhat exposed to the wind, are 
 somewhat disturbed by gusts. 
 
 130. When the amount of snowfall at the station gauge since the last 
 observation has been affected by the action of the wind, the observer 
 will make at least three measurements of the depth at open places in 
 the vicinity of the office, going to some distance if necessary in order 
 to obtain a good record. The mean of these measurements will be 
 recorded as the depth of snow, the snow ''not melted) in the station 
 gauge being given in a footnote. 
 
 131. When it is not practicable to melt the snow in the gauge, or that 
 measured elsewhere, one tenth the depth, giving explanatory footnote, 
 will be recorded as the water equivalent of the precipitation. 
 
 The following suggestions are given for the guidance of observers in the measure- 
 ment of snowfall : 
 
 While one-tenth the depth is arbitrarily adopted as the water equivalent of snow, 
 yet this is only coarsely approximate, and observers should always endeavor to 
 determine the actual equivalent by some of the following methods : 
 
 First method. — Select a place where the precipitation is as little disturbed aspossible 
 and cut out a section with the snow gauge, or 8-inch overflow of rain guage, by sinking 
 the gauge inverted through the snow and covering the mouth with a sheet of tin or 
 a thin board. The 8-inch cylindrical section of snow thus secured is then most con- 
 veniently measured by weighing either in the gauge itself, the weight of which is 
 afterwards deducted, or after first emptying the snow into some smaller or lighter 
 vessel. If this weight can be ascertained with an accuracy of within one-fourth 
 of an ounce, the water equivalent will be given to the nearest hundredth of an inch 
 by use of Table IV. 
 
 Second method. — If the snow is melted and measured in the measuring tube of the 
 rain guage, care must be taken that loss does not occur by evaporation. Rapid 
 melting must be avoided. The best results are obtained, not by melting directly, 
 but by mixing a measured quantity of warm water with the snow and then measuring 
 the slushy mixture, just as if the snow were all melted, deducting, of course, the 
 amount of warm water added. Ten or even five inches of warm water in the meas- 
 uring tube are sufficient for effecting the measurement of n very considerable 6now 
 fall. Care must be taken in changing the snow or water from one vessel to another i 
 
31 
 
 SITIVSHIIVE TABLE I. 
 LOCAL TIME OF SUNRISE AND SUNSET FOE NORTH LATITUDES FROM 25° TO 49°, INCLUSIVE. 
 
 SUNRISE. 
 
 (Ub6 latitude of station, interpolating wlien necessary.] 
 
 HOUKS AND HUNDREDTHS. 
 
 A. M. 
 
 A.M. 
 
 
 Date. 
 
 
 1 
 
 
 11 
 
 
 21 
 
 Feb. 
 
 1 
 
 
 11 
 
 
 21 
 
 
 1 
 
 
 11 
 
 
 21 
 
 Apr. 
 
 1 
 
 11 
 
 
 21 
 
 May 
 
 1 
 
 11 
 
 
 21 
 
 
 1 
 
 
 11 
 
 
 21 
 
 Julv 
 
 1 
 
 
 11 
 
 
 21 
 
 Aug. 
 
 1 
 
 11 
 
 
 21 
 
 Sept. 
 
 1 
 
 
 
 21 
 
 Oct. 
 
 1 
 
 
 11 
 
 
 21 
 
 
 1 
 
 
 11 
 
 
 21 
 
 Dec. 
 
 1 
 
 
 11 
 
 21 
 
 
 
 25° 27° 29° I 31° 33° 35° 3' 
 
 0.78 
 6.78 
 
 6.72 
 6.03 
 6.50 
 
 6.38 
 6.20 
 
 0.03 
 
 5.87 
 5.70 
 5.55 
 
 5.40 
 5.28 
 5.20 
 
 5.15 
 5.15 
 5.17 
 
 5.22 
 
 5.28 
 5.35 
 
 5.43 
 5.52 
 5.60 
 
 5.68 
 5.75 
 5.80 
 
 5.87 
 5.93 
 
 6.0:; 
 
 6.13 
 6.23 
 6.35 
 
 0.83 
 0.85 
 0.83 
 
 0.77 
 6.67 
 6.53 
 
 0.42 
 
 6.22 
 
 0.03 
 
 5.85 
 5.67 
 
 5.50 
 
 5.35 
 5.23 
 5.13 
 
 5.08 
 5.08 
 5.08 
 
 5.15 
 5.22 
 5.30 
 
 5.40 
 5.48 
 5.57 
 
 5.65 
 5.73 
 5.80 
 
 5.97 
 
 0.05 
 
 6. 17 
 0.28 
 0.40 
 
 0. 47 6. 53 
 0. 60 0. 67 
 6.08 I 6.77 
 
 6.90 
 6.92 
 6.90 
 
 0.80 
 6.70 
 6.55 
 
 6.43 
 6.22 
 0.03 
 
 5.83 
 5.63 
 5.47 
 
 5.32 
 5.17 
 5.08 
 
 5. 02 
 5.02 
 5.02 
 
 5.08 
 5.15 
 
 5.23 
 
 5.33 
 
 5. 43 
 5.52 
 
 5.62 
 5.70 
 5.78 
 
 5. SS 
 5.98 
 
 6.60 
 0.73 
 6.83 
 
 0.97 
 6.98 
 6.97 
 
 6.87 
 
 0.75 
 6.58 
 
 6.47 
 6.23 
 6.03 
 
 5.82 
 5.60 
 
 5.43 
 
 5.25 
 5.12 
 
 5.00 
 
 4.92 
 4.92 
 4.93 
 
 4.98 
 5.07 
 5.17 
 
 5.27 
 5.38 
 5. 48 
 
 5. 
 
 6.02 
 
 6.13 
 
 6.27 
 6.38 
 6.53 
 
 7.05 
 7.07 
 7.02 
 
 5.80 
 
 5. 58 
 5.38 
 
 5.20 
 5.05 
 4.92 
 
 4.83 
 4.82 
 4.85 
 
 4.90 
 4.98 
 5.08 
 
 5.20 
 5.32 
 5.45 
 
 5. 58 5. 55 
 5.70 ! 5.68 
 5. 78 5. 78 
 
 5.92 
 6.03 
 6.17 
 
 0.45 
 6.00 
 
 6.75 
 0.88 
 .02 
 
 7.13 
 7.13 
 7.08 
 
 i. 93 
 
 6.82 6.85 
 i. 62 6. 67 
 
 6.50 
 6.27 
 6.02 
 
 5.78 
 5.55 
 5.35 
 
 4.77 
 4.73 
 4.75 
 
 4.80 
 4.90 
 5.00 
 
 5.15 
 5.27 
 5.40 
 
 5.53 
 5.67 
 5.78 
 
 5.92 
 6.05 
 0.20 
 
 6.37 
 6.52 
 
 7.22 
 
 7.22 
 7.17 
 
 7.05 
 
 6.90 
 6.72 
 
 0.53 
 6.27 
 6.02 
 
 5.77 
 5.53 
 5.32 
 
 5.08 
 
 4.92 
 4.78 
 
 4.07 
 4.03 
 4.65 
 
 4.70 
 4.80 
 4.92 
 
 5.07 
 5.20 
 5.37 
 
 5.50 
 5. 65 
 5.78 
 
 5.93 
 6.07 
 6.25 
 
 6.42 
 6.58 
 0.75 
 
 0.92 
 7.07 
 7.17 
 
 39° 
 
 41= 
 
 7.32 
 
 7.42 
 
 7.30 
 
 7.40 
 
 7.25 
 
 7.33 
 
 7.12 
 
 7.18 
 
 6.95 
 
 7.00 
 
 0.75 
 
 6.78 
 
 6.55 
 
 6.58 
 
 C.28 
 
 6.28 
 
 6.02 
 
 6.02 
 
 5.75 
 
 5.73 
 
 5.50 
 
 5.47 
 
 5.27 
 
 5.22 
 
 5.02 
 
 4.97 
 
 4 83 
 
 4.75 
 
 4.70 
 
 4.60 
 
 4.58 
 
 4.48 
 
 4.55 
 
 4.45 
 
 4. 55 
 
 4.45 
 
 4.00 
 
 4.52 
 
 4.70 
 
 4.62 
 
 4.83 
 
 4.75 
 
 5.00 
 
 4.92 
 
 5.15 
 
 5.07 
 
 5.32 
 
 5.25 
 
 5.47 
 
 5.43 
 
 5.62 
 
 5.60 
 
 5.77 
 
 5.77 
 
 5.95 
 
 5.95 
 
 6.10 
 
 6.12 
 
 6.28 
 
 6.33 
 
 6.47 
 
 6.52 
 
 6.65 
 
 6.72 
 
 6.83 
 
 6.92 
 
 7.00 
 
 7.08 
 
 7.15 
 
 7.25 
 
 7.27 
 
 7.38 
 
 7 53 
 7.50 
 7.42 
 
 7.05 
 6.83 
 
 0.62 
 6.30 
 6.00 
 
 5.72 
 5.42 
 5.17 
 
 4.90 
 4.68 
 4.50 
 
 4.37 
 4.32 
 4.32 
 
 4.38 
 4.50 
 4.05 
 
 4.83 
 5.00 
 5. 20 
 
 5. 40 
 5.58 
 5.75 
 
 5.07 
 6.15 
 6.37 
 
 6.58 
 6.80 
 7. 00 
 
 7.20 
 7.37 
 7.50 
 
 45° 
 
 47° 
 
 7.05 
 
 7.78 
 
 7.60 
 
 7.72 
 
 7.52 
 
 7.62 
 
 7.33 
 
 7.42 
 
 7.12 
 
 7.20 
 
 6.87 
 
 6.92 
 
 6.65 
 
 6.68 
 
 6.32 
 
 6.33 
 
 6.00 
 
 6.00 
 
 5.68 
 
 5.67 
 
 5.38 
 
 5.35 
 
 5.16 
 
 5.03 
 
 4.82 
 
 4.73 
 
 4.00 
 
 4.50 
 
 4.40 
 
 4.28 
 
 4.25 
 
 4.12 
 
 4.20 
 
 4.05 
 
 4.20 
 
 4.05 
 
 4.27 
 
 4.13 
 
 4.38 
 
 4.25 
 
 4.55 
 
 4.42 
 
 4.75 
 
 4.65 
 
 4.92 
 
 4.83 
 
 5.13 
 
 5.07 
 
 5.37 
 
 5.33 
 
 5.57 
 
 5.53 
 
 5.75 
 
 5.73 
 
 5.98 
 
 5.98 
 
 6.18 
 
 6.22 
 
 6.40 
 
 6.45 
 
 0.65 
 
 6.72 
 
 6.87 
 
 6.97 
 
 7.10 
 
 7.22 
 
 7.30 
 
 7.42 
 
 7.48 
 
 7.62 
 
 7.60 
 
 7.73 
 
32 
 
 SUNSHINE TABLE I. 
 LOCAL TIME OP SUXBISE AND SUNSET FOB NOBTH LATITUDES FEOM 26° TO 49°, INCLUSIVE. 
 
 SUNSET. 
 
 fUse latitude of station, interpolating "when necessary.) 
 
 HOURS AND HUNDREDTHS. 
 
 Date. 
 
 P.M. 
 
 P.M. 
 
 25° 
 
 5.37 
 5.50 
 5.62 
 
 5.75 
 5.87 
 5.97 
 
 6.05 
 6.13 
 6.20 
 
 6.28 
 6.35 
 6. J 3 
 
 6.52 
 6. f.8 
 
 G. 67 
 
 6.75 
 6.82 
 6.87 
 
 6. 88 
 6.88 
 6.83 
 
 6. 75 
 0.03 
 0.50 
 
 6.33 
 6.15 
 5.97 
 
 5.80 
 5.62 
 5.47 
 
 5.33 
 5.23 
 5.20 
 
 5.17 
 5.20 
 5.27 
 
 27° 
 
 5.30 
 5.43 
 5.57 
 
 5.70 
 5.83 
 
 6.03 
 6.12 
 6.20 
 
 6.30 
 6.37 
 
 6.47 
 
 6.55 
 6.63 
 6.73 
 
 6.82 
 6.88 
 6.95 
 
 6.95 
 6.95 
 6.90 
 
 6.80 
 6.68 
 6.53 
 
 6.35 
 
 6.17 
 5.97 
 
 5.78 
 5.60 
 5. 45 
 
 5.30 
 5.18 
 5.13 
 
 5.10 
 5.13 
 5.20 
 
 29° 
 
 5.23 
 5.37 
 5.50 
 
 5.65 
 5.78 
 5.90 
 
 6.02 
 6.10 
 6.20 
 
 6.32 
 6.40 
 6.50 
 
 6.70 
 6.80 
 
 6.90 
 6.97 
 7.02 
 
 7.03 
 7.03 
 6.97 
 
 6.85 
 6.72 
 6.57 
 
 6.38 
 6.18 
 5.98 
 
 5.77 
 5.58 
 5.42 
 
 5.25 
 5.13 
 5.07 
 
 5.03 
 5.07 
 5.12 
 
 31° 
 
 5.15 
 5.30 
 5.43 
 
 5.60 
 5.75 
 5.88 
 
 6.00 
 6.08 
 
 0.20 
 
 6.33 
 6.42 
 6.55 
 
 6.65 
 6.77 
 6.87 
 
 6.97 
 7.03 
 7.08 
 
 7.10 
 7.12 
 7.05 
 
 6.92 
 6.78 
 6.62 
 
 6.40 
 6.20 
 5.98 
 
 5.77 
 5.57 
 5.37 
 
 5.20 
 5.07 
 5.00 
 
 4.97 
 5.00 
 5.05 
 
 33° 
 
 5. C8 
 5.23 
 5.37 
 
 5.53 
 5.70 
 5.85 
 
 5.97 
 6.07 
 6.22 
 
 6.35 
 6.45 
 6.58 
 
 6.72 
 6.83 
 6.95 
 
 7.05 
 7.13 
 7.18 
 
 7.20 
 7.20 
 7.13 
 
 0.98 
 6.83 
 6.67 
 
 6.43 
 6.22 
 5.98 
 
 5. 75 
 5.53 
 5.33 
 
 5.15 
 5.00 
 4.93 
 
 4.88 
 4. SO 
 4.97 
 
 35° 
 
 37° 
 
 A 
 
 
 6.00 
 
 4.90 
 
 5.15 
 
 5.07 
 
 5,32 
 
 5.23 
 
 5.48 
 
 5.42 
 
 5.65 
 
 5.62 
 
 5.80 
 
 5.77 
 
 5.93 
 
 5.92 
 
 6.07 
 
 6.05 
 
 6.22 
 
 6.22 
 
 6.37 
 
 6.38 
 
 6.48 
 
 6.52 
 
 6.63 
 
 6.68 
 
 6.77 
 
 6.82 
 
 6.88 
 
 6.95 
 
 7.02 
 
 7.10 
 
 7.13 
 
 7.22 
 
 7.23 
 
 7.32 
 
 7.28 
 
 7.38 
 
 7.30 
 
 7.38 
 
 7.27 
 
 7.35 
 
 7.20 
 
 7.28 
 
 7.05 
 
 7.12 
 
 0.90 
 
 6.95 
 
 6.70 
 
 6.73 
 
 6.47 
 
 6.50 
 
 0.23 
 
 6.25 
 
 5.98 
 
 5.98 
 
 5.75 
 
 5.73 
 
 5.52 
 
 5.48 
 
 5.30 
 
 5.27 
 
 5.10 
 
 5.05 
 
 4.95 
 
 4.88 
 
 4.87 
 
 4.78 
 
 4.80 
 
 4.72 
 
 4.82 
 
 4.72 
 
 4.88 
 
 4.78 
 
 39° 
 
 4.80 
 4.98 
 5.13 
 
 5.35 
 5.55 
 5.73 
 
 5.90 
 6.05 
 6.22 
 
 6.40 
 6.55 
 6.73 
 
 7.02 
 7.18 
 
 7.32 
 
 7.42 
 7.48 
 
 7.48 
 7.45 
 7.35 
 
 7.20 
 7. CO 
 6.78 
 
 0.53 
 6.27 
 5.98 
 
 5.72 
 5.47 
 5.23 
 
 5.00 
 4.82 
 4.70 
 
 4.63 
 4.63 
 4.70 
 
 41° 
 
 4.72 
 4.88 
 5. 05 
 
 5.27 
 5.52 
 5.68 
 
 5.87 
 6.03 
 0.22 
 
 6.42 
 6.58 
 6.78 
 
 6.95 
 7.10 
 7.27 
 
 7.42 
 7.52 
 7.58 
 
 7.60 
 7.55 
 7.45 
 
 7.28 
 7.07 
 6.83 
 
 6.57 
 6.28 
 
 5.72 
 5.45 
 5.18 
 
 4.95 
 
 4.75 
 4.62 
 
 4.55 
 4.55 
 4.60 
 
 43° 
 
 4.60 
 4.78 
 4,97 
 
 5.20 
 5.45 
 5.65 
 
 5.83 
 6.03 
 6.23 
 
 6.43 
 0.62 
 6.83 
 
 7.02 
 7.20 
 7.37 
 
 7.53 
 7.63 
 7.72 
 
 7.72 
 7.67 
 7.55 
 
 7.37 
 7.15 
 6.90 
 
 6.60 
 6.30 
 6.00 
 
 5.70 
 5.42 
 5.13 
 
 4.88 
 4.67 
 4.53 
 
 4.45 
 4.43 
 4.48 
 
 
 45° 
 
 4.48 
 4.68 
 
 4.88 
 
 5.13 
 5.38 
 5.60 
 
 5.80 
 6.02 
 
 0.23 
 
 6.47 
 6.67 
 6.90 
 
 7.10 
 7.28 
 7.47 
 
 7.65 
 
 7.77 
 7.83 
 
 7.83 
 7.78 
 7.65 
 
 7.45 
 7.23 
 0.95 
 
 6.63 
 6.33 
 6.00 
 
 5.68 
 5.38 
 5.10 
 
 4.82 
 4.60 
 4.43 
 
 4.33 
 4.32 
 4.37 
 
 47° 
 
 4.35 
 4.57 
 4.78 
 
 5.05 
 5.30 
 5.57 
 
 5.77 
 6.00 
 6.23 
 
 6.48 
 6.72 
 6.97 
 
 7.18 
 7.38 
 7.60 
 
 7.78 
 7.92 
 7.98 
 
 7,98 
 7.92 
 
 7.77 
 
 7.55 
 7.32 
 7,02 
 
 6.35 
 6.00 
 
 5.67 
 5.35 
 5.03 
 
 4.75 
 4.50 
 4.32 
 
 4.22 
 4.18 
 4.23 
 
33 
 
 Date. 
 
 Apr. 
 
 I. 
 11. 
 21. 
 
 1- 
 11. 
 21. 
 
 1-. 
 11. 
 21.. 
 
 1.. 
 11.. 
 21.. 
 
 1. 
 11. 
 21. 
 
 1. 
 
 11. 
 21. 
 
 Mf-V'SHI-VE TABLE II. 
 
 TABLE OF APPROXIMATE HOURS OF POSSIBLE SUNSHINE. 
 FROM 25° TO 49° NORTH LATITUDE, INCLUSIVE. 
 
 [Use latitude of station, interpolating when necessary.] 
 
 26= i 27° 29" 31° 
 
 10.6 
 
 10.7 
 10.8 
 
 10. 5 | 10. 3 
 
 10. 6 I 10. 4 
 
 10.7 10.6 
 
 May 
 
 1 
 
 11 
 
 
 21 
 
 
 1 
 
 
 11 
 
 21 
 
 July 
 
 1 
 
 11 
 
 
 21 
 
 Aug. 
 
 1 
 
 11 
 
 
 21 
 
 Sept. 
 
 
 11 
 
 
 21 
 
 Oft. 
 
 1 
 
 
 
 
 21 
 
 
 
 11.0 I 10.9 
 11.2 I 11.2 
 
 11.5 I 11 4 
 
 I 
 
 11.9 
 12.2 
 
 12.4 
 12.7 
 13.0 
 
 13.2 
 13.4 
 13.6 
 
 13.7 
 13.8 
 13.9 
 
 13.8 
 13.7 
 13.6 
 
 13.4 
 13.2 
 13.0 
 
 12.7 
 12.4 
 12.2 
 
 11.9 
 11.0 
 
 11.4 
 
 11.1 
 10.9 
 
 10.7 
 
 10.0 
 10.5 
 10.4 
 
 11.7 
 11.9 
 
 12.2 
 
 12.4 
 
 12.6 
 
 12.9 
 
 13.1 
 
 13.3 
 
 13.5 
 
 13.6 
 
 13.7 
 
 13.7 
 
 13.7 
 
 13.6 
 
 13.5 
 
 13.3 
 
 13.1 
 
 12.9 
 
 12.6 
 
 12.4 
 
 12.2 
 
 11.9 
 
 11.7 
 
 11.4 
 
 11. 
 
 11.0 
 10.8 
 
 10.7 
 10.6 
 10.6 
 
 10. 8 
 11.1 
 11.4 
 
 11.0 
 11.9 
 12.2 
 
 12.5 
 12.8 
 13.0 
 
 13.3 
 13.5 
 13.7 
 
 13.9 
 14.0 
 14.0 
 
 14.0 
 13.9' 
 13.7 
 
 13.5 
 13.3 
 13.0 
 
 12.8 
 12.5 
 12.2 
 
 11.9 
 11.0 
 11.3 
 
 11.0 
 
 10.8 
 10.6 
 
 10.4 
 10.3 
 10.3 
 
 10.2 
 10.3 
 
 10.5 
 
 10.7 
 11.0 
 11.3 
 
 11.5 
 11.8 
 12.2 
 
 12.5 
 12.8 
 13.1 
 
 13.4 
 13. C 
 13.9 
 
 14.0 
 14.1 
 14.1 
 
 14.1 
 14.0 
 13.9 
 
 13.6 
 13.4 
 13.1 
 
 12.8 
 12.5 
 12.2 
 
 11.9 
 11.6 
 11.2 
 
 10.9 
 10.7 
 10.5 
 
 10.3 
 10.2 
 10.1 
 
 33° 
 
 35° 
 
 10.0 
 
 9.9 
 
 10.2 
 
 10.0 
 
 10.4 
 
 10.2 
 
 10.6 
 
 10.5 i 
 
 12.0 
 12.9 
 13.2 
 
 13.5 
 13.8 
 
 14.0 
 
 14.2 
 14.3 
 14.3 
 
 14.3 
 14.2 
 14.0 
 
 13.8 
 13.5 
 13.2 
 
 12.9 
 12.5 
 
 12.2 
 
 11.8 
 
 11.5 
 11.2 
 
 10.8 
 10.6 
 
 10.3 
 
 10. 1 
 10.0 
 10.0 
 
 12.6 
 12.9 
 13.3 
 
 13.6 
 13.9 
 
 14.2 
 
 14.4 
 14.5 
 14.5 
 
 14.5 
 14.4 
 14.2 
 
 13.9 
 13.6 
 13.3 
 
 12.9 
 12.6 
 12.2 
 
 11.8 
 11.5 
 11.1 
 
 10.7 
 10.4 
 10.2 
 
 10.0 
 9.8 
 9.8 
 
 10.4 
 
 10.9 10.8 | 10.7 
 11.2 11.1 ! 11.0 
 
 11.5 ' 11.4 11.4 
 11.8 i 11.8 11.8 
 12. 2 12. 2 | 12. 2 
 
 12.6 
 13.0 
 13.4 
 
 13.7 
 14.0 
 14.3 
 
 14.6 
 
 14.7 
 14.7 
 
 14.7 
 14.6 
 14.4 
 
 14.0 
 13.8 
 13.4 
 
 13.0 
 12.6 
 12.2 
 
 11.8 
 1X4 
 11.0 
 
 10.6 
 10.3 
 
 10.0 
 
 9.8 
 9.0 
 9.0 
 
 39° 
 
 10.2 
 10.6 
 11.0 
 
 11.4 
 11.8 
 12.2 
 
 12.6 
 13.0 
 13.5 
 
 13.9 
 
 14.2 
 14.5 
 
 14.7 
 14.9 
 14.9 
 
 14.9 
 14.8 
 14.5 
 
 14.2 
 13.8 
 13.5 
 
 13.1 
 12.6 
 12.2 
 
 11.8 
 11.4 
 11.0 
 
 10.5 
 10.2 
 
 9.5 
 
 9.4 
 
 9.3 
 9.5 
 
 9.7 
 
 10.1 
 10.5 
 10.9 
 
 11.3 
 
 11.8 
 
 12.2 
 
 12.7 
 
 13.1 
 
 13.6 
 
 14.0 
 
 14.4 
 
 14.7 
 
 14.9 
 
 15.1 
 
 15.1 
 
 15.1 
 
 14.9 
 
 14.7 
 
 14.4 
 
 14.0 
 
 13.6 
 
 13.1 
 
 12.7 
 
 12.2 
 
 11.8 
 
 11.3 
 
 10.8 
 
 10.4 
 
 10.0 
 
 9.7 
 
 9.5 
 
 9.3 
 
 9.2 
 
 10.0 
 10.4 
 10.8 
 
 11.2 
 
 11.7 
 12.2 
 
 12.7 
 13.2 
 
 13.7 
 
 14.1 
 
 14. 5 
 14.9 
 
 15.2 
 15.3 
 15.4 
 
 15.3 
 15.2 
 14.9 
 
 14.5 
 14.2 
 13.7 
 
 13.2 
 12.7 
 12.2 
 
 11.7 
 11.3 
 
 10.8 
 
 10.3 
 
 10.7 
 
 11.2 
 11.7 
 12.2 
 
 9.1 
 
 9.0 
 
 12.8 
 
 13.3 
 
 13.8 
 
 14.3 
 
 14.7 
 
 15.1 
 
 15.4 
 
 15.6 
 
 15.6 
 
 15.6 
 
 15.4 
 
 15.1 
 
 14.7 
 
 14.3 
 
 13.8 
 
 13.3 
 
 12.8 
 
 12.2 
 
 11.7 
 
 11.2 
 
 10.7 
 
 10.2 
 
 9.7 
 
 9.3 
 
 9.0 
 
 8.8 
 
 8.8 
 
 47° 
 
 8.6 
 
 8.8 
 
 9.2 
 
 9.6 
 
 10.1 
 
 10.6 
 
 11.1 
 
 11.7 
 
 12.2 
 
 12.8 
 
 13.4 
 
 13.9 
 
 14.4 
 
 14.9 
 
 15.3 
 
 15.7 
 
 15.9 
 
 15.9 
 
 15.8 
 
 15.7 
 
 15.4 
 
 14.9 
 
 14.5 
 
 14.0 
 
 13.4 
 
 12.8 
 
 12.3 
 
 11.7 
 
 11.1 
 
 10.6 
 
 10.0 
 
 9.5 
 
 9.1 
 
 8.8 
 
 6581- 
 
 -3 
 
34 
 
 SUNSHINE TABLE III. 
 
 MONTHLY AMOUNTS OP POSSIBLE SUNSHINE FOK HOURS ENDING— 
 
 SHORTLY AFTER SUNRISE. 
 
 [From 25° to 49° north latitude, inclusive.] 
 
 HOURS AND TENTHS. 
 
 Month. 
 
 A.M. 
 
 25° 
 
 27° 
 
 29° 
 
 31° 
 
 83° 
 
 35° 
 
 37° 
 
 39° 
 
 41° 
 
 43° 
 
 45- 
 
 47- 
 
 49° 
 
 
 7 
 8 
 
 7 
 
 8 
 7 
 
 S 
 
 6 
 
 r 
 
 6 
 
 5 
 
 <> 
 
 4 
 
 5 
 6 
 
 5 
 
 
 5 
 6 
 
 
 
 6 
 
 7 
 
 7 
 
 8 
 
 7 
 
 8 
 
 7.1 
 
 5.3 
 
 3.4 
 
 1.4 
 
 0.3 
 30.0 
 
 7.4 
 
 
 
 
 
 
 
 
 28.2 
 6.4 
 
 25.7 
 
 5.1 
 27.9 
 
 5.5 
 28.9 
 
 1.1 
 25.4 
 
 23.1 
 
 4.2 
 27.5 
 
 4.5 
 28.5 
 
 1.2 
 25.2 
 
 20.3 
 
 3.5 
 27.0 
 
 3.8 
 28.0 
 
 1.2 
 24.8 
 
 17.5 
 
 2.7 
 26.3 
 
 3.0 
 27.3 
 
 1.2 
 24.6 
 
 0.1 
 20.6 
 
 12.2 
 
 14.4 
 
 2.1 
 25.3 
 
 2.4 
 20.3 
 
 1.5 
 24.2 
 
 0.5 
 
 11.0 
 
 1.6 
 24.0 
 
 1.8 
 25.0 
 
 1.6 
 
 23.9 
 
 1 
 
 
 Feb. 28d 
 
 11.8 
 
 10.8 
 
 10.1 
 
 8.8 
 
 1.1 
 22.7 
 
 Feb. 29d 
 
 12.4 
 
 11.3 
 
 10.6 
 
 9.3 
 
 7.9 
 
 6.8 
 
 1.3 
 23.1 
 
 Mar 
 
 April 
 
 May 
 
 0.5 
 26.7 
 
 0.6 
 26.4 
 
 0.7 
 26.3 
 
 0.8 
 26.0 
 
 0.9 
 25.8 
 
 1.0 
 25.6 
 
 1.8 
 23. a 
 
 1 8 
 
 10.0 
 
 12.1 
 
 13.0 
 
 14.1 
 
 0.4 
 28.4 
 
 15.1 
 
 1.0 
 29.5 
 
 16.1 
 
 2.6 
 30.2 
 
 17.0 
 
 4.6 
 30.8 
 
 18.2 
 7.0 
 
 19.3 
 9.5 
 
 21.7 22.6 
 15. 1 1 8. 4 
 
 23.1 
 21.8 
 
 23.0 
 
 24.8 
 
 26.6 
 
 
 
 
 
 i 
 
 t 
 
 
 2 1 
 
 
 
 
 
 
 2.0 
 
 4.7 
 
 7.3 
 
 10.3 
 
 13.1 
 
 16.0 
 
 19.9 
 
 23.4 
 
 27.8 
 
 
 
 23. 
 
 27.2 
 
 29.2 
 
 
 July 
 
 
 0.6 
 29.3 
 
 2.2 
 30.3 
 
 4.4 
 30.9 
 
 7.0 
 
 9.6 
 
 12.9 
 
 16.2 
 
 20.1 
 
 24.) 
 
 21.1 
 
 22.8 
 
 24.9 
 
 27.3 
 
 
 Aug 
 
 Sept 
 
 
 0.2 
 25.7 
 
 9.7 
 
 0.1 
 23.9 
 
 6.1 
 29.8 
 
 0.9 
 26.9 
 
 10.1 
 
 2.0 
 27.9 
 
 10.3 
 
 3.3 
 
 28.8 
 110 
 
 5.0 
 
 13.7 
 
 0.8 
 
 1.2 
 30.1 
 
 21.4 
 
 14.7 
 
 7.0 
 
 0.8 
 2!). 7 
 
 19.9 
 
 16.3 
 
 7.7 
 
 0.8 
 29.2 
 
 18.2 
 
 17.8 
 
 7.9 
 
 0.5 
 28.2 
 
 16.4 
 
 19.3 
 
 8.2 
 
 0.4 
 27.5 
 
 14.4 
 
 20.7 
 
 8.5 
 
 0.3 
 26.7 
 
 12.4 
 
 22.4 
 
 8.8 
 
 0.2 
 25.8 
 
 10.2 
 
 23. a 
 
 9.3 
 
 0.1 
 24.9 
 
 8.1 
 
 29.6 
 11.4 
 
 Oct 
 
 
 
 Nov 
 
 22.8 
 
 4.2 
 29.1 
 
 21.7 
 
 3.0 
 27.9 
 
 20. (i 
 
 1.7 
 20.0 
 
 19.2 
 
 0.9 
 23.8 
 
 Dec 
 
 11.4 
 
 9.2 
 
 7.2 
 
 4.8 
 
 2.5 
 
 1.0 
 29.0 
 
 0.2 
 
 27.7 
 
 
 
 
 25.2 
 
 21.9 
 
 18.3 
 
 15.0 
 
 11.0 
 
 
 
 
 
 
 
 
 
 SHORTLY AFTER SUNSET. 
 
 Month. 
 
 P.M. 
 
 25° 
 
 27° 
 
 29° 
 
 31° 
 
 33° 
 
 35° 
 
 37° 
 
 30.6 
 5.0 
 
 18.6 
 
 39° 
 
 29.8 
 3.1 
 
 17.2 
 
 41° 
 
 43° 
 
 45° 
 
 47° 
 
 49° 
 
 Jan 
 
 5 
 « 
 
 6 
 
 7 
 6 
 
 7 
 
 6 
 7 
 
 7 
 
 8 
 7 
 8 
 
 7 
 
 8 
 9 
 
 7 
 8 
 9 
 
 7 
 8 
 
 6 
 
 7 
 
 5 
 « 
 
 5 
 6 
 
 5 
 6 
 
 
 
 
 
 
 
 28.4 
 1.7 
 
 15.9 
 
 20.5 
 0.9 
 
 14.4 
 
 24.1 
 0.3 
 
 12.9 
 
 21.1 
 
 17.4 
 
 17.2 
 
 25.0 
 0.1 
 
 26.0 
 0.1 
 
 15.4 
 24.1 
 
 13.4 
 23.0 
 
 11.3 
 22.2 
 
 9.3 
 21.0 
 
 7.2 
 19.6 
 
 
 Feb. 28d 
 
 11.1 
 
 9.4 
 
 Feb. 29d 
 
 25.1 
 
 24.0 
 
 23.2 
 
 21.8 
 
 20.5 
 
 19.4 
 
 18.0 
 
 16.6 
 
 15.2 
 
 13.6 
 
 ii.8 
 
 10.0 
 
 Mar 
 
 
 
 
 30.9 
 4.6 
 
 15.4 
 
 30.8 
 4.6 
 
 16.6 
 
 30.7 
 4.5 
 
 17.8 
 
 30.6 
 4.6' 
 
 19.0 
 
 30.4 
 4.6 
 
 20.2 
 
 30.2 
 4.8 
 21.5 
 
 30.0 
 4.9 
 
 23.1 
 0.2 
 
 29.8 
 4.9 
 
 24.2 
 0.7 
 
 29.3 
 
 April 
 
 5.2 
 11.8 
 
 5.0 
 12.5 
 
 4.9 
 13.4 
 
 4.6 
 
 14.4 
 
 5.2 
 
 25.2 
 1.4 
 
 Ma ' 
 
 19.5 
 
 21.1 
 
 23.1 
 
 25.1 
 
 27.4 
 0.1 
 
 28.6 
 0.7 
 
 29.6 
 2.0 
 
 30.4 
 3.6 
 
 30.9 
 5.7 
 
 
 
 • 
 
 8.6 
 
 11.6 
 
 15.1 
 
 18.6 
 
 j 
 
 25.0 
 
 27.2 
 
 29.2 
 0.3 
 
 29.9 
 1.6 
 
 
 
 4.4 
 
 7.2 
 
 9.9 
 
 12.9 
 
 16.0 
 
 19.7 
 
 23.3 
 
 27.8 
 
 29.7 
 
 
 
 
 2.3 
 
 Jul 
 
 26.2 
 
 28.2 
 
 30.1 
 0.4 
 
 30.8 
 2.1 
 
 
 
 
 
 
 
 
 
 
 ^ 
 
 4.4 
 
 6.6 
 
 9.1 
 
 11.9 
 
 15.0 
 
 18.2 
 
 21.5 
 
 25.3 
 
 28.3 
 
 
 
 
 0.9 
 
 
 17.4 
 
 18.6 
 
 19.7 
 
 21.3 
 
 22.9 
 
 24.3 
 0.1 
 
 28.8 
 4.8 
 
 25.3 
 0.5 
 
 28.7 
 5.1 
 
 26.4 
 1.1 
 
 28.7 
 5.5 
 
 27.3 
 2.0 
 
 28.7 
 5.9 
 
 28.1 
 3.2 
 
 28.7 
 6.3 
 
 30.7 
 9.1 
 
 18.8 
 
 28.8 
 4.6 
 
 28.6 
 6.8 
 
 30.5 
 8.3 
 
 16.4 
 
 29.5 
 6.3 
 
 28.5 
 7.2 
 
 29.9 
 7.4 
 
 13.2 
 
 30.1 
 
 
 
 Sept 
 
 28.9 
 3.2 
 
 28.8 
 3.4 
 
 28.8 
 3.8 
 
 28.8 
 4.1 
 
 28.8 
 4.4 
 
 28.5 
 7.8 
 
 29.2 
 
 
 17.2 
 
 16.6 
 
 15.7 
 
 14.7 
 
 29.8 
 1.8 
 
 30.8 
 1.3 
 
 13.7 
 
 28.8 
 0.8 
 
 29.2 
 0.3 
 
 12.9 
 
 27.4 
 0.4 
 
 26.9 
 
 11.8 
 
 25.6 
 0.1 
 
 23.9 
 
 10.8 
 23.5 
 
 10.2 
 21.3 
 
 6.7 
 10.2 
 
 
 6.9 
 
 5.2 
 
 3.5 
 
 
 
 21.2 
 
 18.4 
 
 14.9 
 
 11.3 
 
 7.2 
 
 3.2 
 
 
 7.6 
 
 5.5 
 
 3.3 
 
 
 
 
 
 
 
 
 
 i 
 
 (Use latitude of station, interpolating when necessary.) 
 
 Note Owing to the peculiar law of Tariation of the numbers in this table, interpolation in certain 
 
 cases is attended with considerable difficulty. If an observer is in doubt in any case of this kind he 
 will write to this office for the correct number. 
 
35 
 
 TABLE IV. 
 
 SHOWING DEPTH OP PRECIPITATION CORRESPONDING TO GIVEN WEIGHTS. 
 
 [Computed for 8-incli circular collector; water at maximum density: 39° F.] 
 
 Weight.! 
 
 Rainfall (inches). 
 
 |i 
 
 j oz. ! \ oz. £ oz. \ oz. ; 
 
 Rainfall (inches). 
 
 oz. \ oz. 4. oz - £ oz - 
 
 Lbs. i 
 
 1 
 1 
 
 1 2 
 1 3 
 1 4 
 1 5 
 1 6 
 1 7 
 1 8 
 1 9 
 1 10 
 1 11 
 1 12 
 1 13 
 
 .00 
 .03 
 :07 
 .10 
 .14 
 .17 
 .21 
 .24 
 .28 
 .31 
 .34 
 .38 
 .41 
 .45 
 .48 
 .52 
 .55 
 .58 
 .62 
 .65 
 .69 
 .72 
 .76 
 
 .93 
 
 .96 
 
 1.00 
 
 .01 
 .04 
 .08 
 .11 
 .15 
 .18 
 .22 
 .25 
 .28 
 .32 
 .35 
 .39 
 .42 
 .46 
 .49 
 .52 
 .56 
 .59 
 .63 
 .00 
 .70 
 .73 
 .77 
 
 .87 
 .90 
 .94 
 
 .02 
 .05 
 .09 
 .12 
 .15 
 .19 
 .22 
 .26 
 .29 
 .33 
 .36 
 .40 
 .43 
 .40 
 .50 
 .53 
 .57 
 .60 
 .04 
 .67 
 
 .03 
 .06 
 .09 
 .13 
 .16 
 .20 
 .23 
 .27 
 .30 
 .34 
 .37 
 .41 
 .44 
 .47 
 .51 
 .54 
 .58 
 .61 
 .65 
 
 .71 
 
 .71 
 
 .74 
 
 .75 
 
 .77 
 
 .78 
 
 .81 
 
 .82 
 
 .84 
 
 .85 
 
 .88 
 
 .89 
 
 .91 
 
 .92 
 
 .94 
 
 .95 
 
 .98 
 
 .99 
 
 1.01 
 
 1.02 
 
 Lbs. oz. 
 1 14 
 
 1 15 
 
 2 
 2 1 
 
 2 8 
 2 9 
 2 10 
 2 11 
 2 12 
 2 13 
 2 14 
 
 2 15 
 
 3 
 3 1 
 
 3 2 
 3 3 
 3 4 
 3 5 
 3 6 
 3 7 
 3 8 
 3 9 
 3 10 
 3 11 
 
 1.03 
 
 1.07 
 1.10 
 1.14 
 1.17 
 1.20 
 1.24 
 1.27 
 1.31 
 1.34 
 1. 38 
 1.41 
 1.44 
 1.48 
 1.51 
 1. 55 
 1.58 
 1.62 
 1.65 
 1.69 
 1.72 
 1.75 
 1.79 
 1.82 
 1.86 
 1.89 
 1.93 
 1.96 
 2.00 
 2.03 
 
 1 1.04 
 
 [ 1.08 
 
 ! 1.11 
 
 j 1.14 
 
 1 1.18 
 
 I 1.21 
 
 I 
 
 I 1.25 
 
 1.28 
 1.32 
 1.35 
 1. 38 
 1.12 
 1.45 
 1.49 
 1.52 
 1.50 
 1.59 
 1.03 
 1.06 
 1.09 
 1.73 
 1.76 
 1.80 
 1.83 
 1.87 
 1.90 
 1.94 
 1.97 
 2.00 
 2.04 
 
 1.05 
 1.08 
 1.12 
 1.15 
 1.19 
 1.22 
 1.26 
 1.29 
 1.32 
 1.36 
 1.39 
 1.43 
 1.40 
 1.50 
 1.53 
 1.57 
 1.00 
 1.63 
 1.67 
 1.70 
 1.74 
 1.77 
 1.81 
 1.84 
 1.87 
 1.91 
 1.94 
 1.98 
 2.01 
 2.05 
 
 1.00 
 1.09 
 1.13 
 1.16 
 1.20 
 1.23 
 1.26 
 1.30 
 1.33 
 1.37 
 1.10 
 1.44 
 1.47 
 ].5I 
 1.54 
 1.57 
 1.61 
 1.64 
 1.68 
 1.71 
 1.75 
 1.78 
 1.81 
 1.85 
 1.88 
 1.92 
 1.95 
 1.99 
 2.02 
 2.06 
 
 Weight 
 
 Lbs. oz. 
 3 12 
 3 13 
 3 14 
 
 3 15 
 
 4 
 4 1 
 4 2 
 4 3 
 4 4 
 4 5 
 
 Rainfall (inches). 
 
 oz. j i oz. 4. oz. 2 <>z 
 
 l 2.06 
 [ 2.10 
 
 2.13 
 j 2.17 
 1 2.20 
 
 2.24 
 
 4 6 
 4 7 
 1 8 
 4 9 
 4 10 
 4 11 
 4 12 
 4 13 
 4 14 
 
 4 15 
 
 5 
 5 1 
 o 2 
 
 3 
 4 
 
 2.30 
 2.34 
 
 2.37 
 2.41 
 2.44 
 2.48 
 2.51 
 2.55 
 2.58 
 2.01 
 2.65 
 2.68 
 2.72 
 2.75 
 2.79 
 
 2.92 
 2.96 
 2.99 
 
 2.07 
 2.11 
 2.14 
 2.18 
 2.21 
 2.24 
 2.28 
 2.31 
 2.35 
 2.38 
 2.42 
 2.45 
 2.49 
 2.52 
 2.56 
 2.59 
 2.62 
 2.66 
 2.69 
 2.73 
 2.76 
 2.80 
 2.83 
 2.86 
 2.90 
 2.93 
 2.97 
 3.00 
 
 2.08 
 2.12 
 2.15 
 2.18 
 2.22 
 2.25 
 2.29 
 2.32 
 2.36 
 2.39 
 2.43 
 2.46 
 2.49 
 2.53 
 2, 50 
 2.60 
 2 63 
 
 2.67 
 
 2.70 
 
 2.73 
 
 2.77 
 
 2.60 
 
 2.84 
 
 2.87 
 
 2.91 
 
 2.94 
 
 2.98 
 
 3.01 
 
 2.09 
 2.12 
 2.16 
 2.19 
 2.23 
 2.26 
 2.30 
 2 33 
 2.37 
 2.40 
 2.43 
 2.47 
 2.50 
 2.54 
 2.57 
 2.61 
 2.64 
 2.67 
 2.71 
 2.74 
 2.78 
 2.81 
 2.85 
 2.88 
 2.92 
 2.95 
 2.08 
 3.02 
 
 Note. — This table is designed especially for the measurement of Snowfall, and is 
 compiled for use in connection with the standard U. S. Weather Bureau 8-inch gauge. 
 
INDEX. 
 
 Paragraph. 
 
 Anemometers changed, how noted 37 
 
 Barograph, set to true pressure '. 57 
 
 Set for time 59 
 
 Time error 63 
 
 Base number, Form 1026 73 
 
 Calm, how recorded 39 
 
 Charts, sunshine, sensitized, care of, before use 79 
 
 How prepared 76 
 
 When prepared 77 
 
 When changed 78 
 
 How changed 81 
 
 How made permanent 8^ 
 
 How preserved 83 
 
 Check marks, direct and reverse 97 
 
 Clocks, how regulated 65 
 
 Correction card (thermograph), how used 68 
 
 Corrections to barograph and thermograph, how obtained 69 
 
 Corrections to barograph or thermograph, at special readings, how used 61 
 
 Correction to instrumental record, how entered on Form 1026 70 
 
 Cylinders, lost motion in 22 
 
 Daily range (Form 1026) 71 
 
 Dial readings 23, 36 
 
 Divisors for obtaining percentages of possible sunshine 94 
 
 Eye readings 69 
 
 Footings (Form 1026) 74 
 
 Form 1001-Metl., miles and directions, how entered.- 39 
 
 1015-Metl., when used for rainfall record 44 
 
 1021-Metl., hourly wind direction, how recorded 40 
 
 When forwarded 40 
 
 1022-Metl., hourly wind movement, how entered 38 
 
 1026-Metl. (base number) 73 
 
 (Footings) 74 
 
 (Hourly readings) 70 
 
 (Range of temperature) ..-. 71 
 
 (Eange of thermograph) 72 
 
 When mailed 75 
 
 1040-Metl., incomplete rainfall records, how tabulated 127 
 
 Maximum rates of precipitation, how recorded 128 
 
 Mixed rain and snow, how recorded 124 
 
 Precipitation, during night, time not kuown, how tabulated 126 
 
 Rainfall by station gauge 123 
 
 Snowfall, how recorded 124 
 
 Tabulation of rainfall records 122 
 
 Time of beginning and ending of precipation, how recorded 125 
 
 37 
 
38 
 
 Paragraph. 
 
 Form 1065-Metl. , how prepared 83 
 
 1070-Metl., accumulation of twilight correction error, how avoided 95 
 
 Data tabulated on 83 
 
 Decimals in sums and means 94 
 
 Duration of sunshine, how recorded 84 
 
 How prepared 49 
 
 Percentage of possible sunshine 93 
 
 Sunshine tabulated on local time • 85 
 
 "Total" 91 
 
 Twilight correction 88 
 
 Hourly readings, how entered on Form 1026 : 70 
 
 Hours of possible sunshine : 92 
 
 Ink, kind used in registering pens 66 
 
 Ink pads, wind direction, felt renewed 12, 13 
 
 Instructions, special, as to value, etc Page 5. . 
 
 Lost motion of cylinders 22, 60 
 
 Maximum temperature (Form 1 026) 71 
 
 Minimum temperature (Form 1026) 71 
 
 Pens, how cared for 66 
 
 Barograph, adjustment of 55, 58 
 
 Thermograph, adjustment of 55, 58 
 
 Register, adjustment ou triple register 21 
 
 Care of 1-9 
 
 Rainfall and sunshine 21 
 
 When renewed 9 
 
 Percentage of possible sunshine (Form 1070) .. .' 93 
 
 Divisors for obtaining 94 
 
 Precipitation, beginning and ending of, how determined 96 
 
 How recorded 97 
 
 During night, how recorded 98 
 
 "Range of thermograph" (Form 1026) 72 
 
 Rainfall, hourly amounts, how entered on record sheet 43 
 
 Maximum rate, how recorded 45 
 
 Raiu gauge, recording float, emptied before overflow 43 
 
 Precipitation data from, entered on Form 1017 42 
 
 Stick measurements from 41 
 
 Weighing, how adjusted for new sheet 101 
 
 Adj ustment after rainfall 105 
 
 Not adjusted at noon during rainfall 107 
 
 Adjusted other than at noon 108 
 
 Readjustment after. accidental disturbance 115 
 
 Clock, how wound and regulated 100 
 
 Disturbed by wind 113 
 
 Explanation of record sheets from . - .• 118 
 
 Explanation of sample record 1 19 
 
 False record to be noted 114 
 
 Pen reset at noon _ 102, 103 
 
 Rate of rainfall, how determined 120, 121 
 
 Scale reading 110 
 
 Scale readings during absence of rainfall 113 
 
 Scale reading, how obtained when gauge fails to record Ill 
 
 Securing cover and door 116 
 
 Sheets changed and dated 104 
 
 Sheet changed at noon 100 
 
 Sheet not changed at noon 106 
 
39 
 
 Eain gauge — Continued. 
 
 Weighing — Continued. Paragraph. 
 
 Sheet changed after rain 105 
 
 Stick measurements, when taken 112 
 
 Test before emptying 109 
 
 Weekly test of 117 
 
 Time of precipitation, how determined 118 
 
 Recording instruments to be kept neat and clean 15 
 
 Register clocks examined . 25 
 
 Registers, triple, double, or single, wind velocities from 1 
 
 Records from recording float gauge 99 
 
 Sunshine and rainfall, when recorded on same sheet 48 
 
 Sunshine, triple register, adjustment of pen 21 
 
 Wind velocity, triple register, adj ustment of pen 21 
 
 Wind direction, centered 1& 
 
 From triple registers, caution against errors in 50 
 
 Imperfect, not to he destroyed Page 7 . . 
 
 Imperfect, how to treat Page 7 .. 1 
 
 Incomplete, how treated 23 
 
 Record sheets " blotted" 10 
 
 When changed . 16 
 
 How mailed 21 
 
 Barograph and thermograph, when mailed 75 
 
 How placed on registers 18 
 
 How trimmed 17 
 
 Barograph and thermograph, adjustment of 55 
 
 When changed 52, 53, 54 
 
 How marked 51, 51 
 
 Renumbered for extreme temperature or pressure 61 
 
 Slides of sunshine recorder, when set 8C 
 
 Snowfall, difficulty of measuring 12S 
 
 Depth of, how determined _ 130 
 
 Water equivalent, how determined 131 
 
 Noted on Form 1028 105 
 
 Sunrise and sunset, character of, how determined 87 
 
 How recorded 80 
 
 Sunshine, hours of possible 92 
 
 Percentage of possible, how obtained 93, 94 
 
 Sunshine charts, photographic, care of, before using 79 
 
 When prepared 77 
 
 How prepared 76 
 
 When changed 78 
 
 How changed 81 
 
 How made permanent 82 
 
 How preserved 83 
 
 ' Sunshine, data compiled 83 
 
 Duration of, recorded 84 
 
 Tabulated on local time 83 
 
 Sunshine recorder, slides of, when set 80 
 
 Sunshine records, thermometrie 4(j 
 
 Best adjustment for instrument il 
 
 Conditions of registration 4/J 
 
 Table I. Local time of sunrise and sunset Page 32.. 88 
 
 II. Approximate hours of possible sunshine Page 33.. 92 
 
 III. Monthly amounts of possible sunshine Page 34.. 94 
 
 IV. Dejrth of precipitation corresponding to given weights Page 35 . . 131 
 
40 
 
 Paragraph. 
 
 Thermograph, set to true temperature 56 
 
 Set for time 59 
 
 Time error 62 
 
 Time adjustment, triple registers 20 
 
 "Total," Form 1070 91 
 
 Trace sheets, barograph arid thermograph, when mailed 75 
 
 Twilight correction, column headed, Form 1070 90 
 
 How determined from Table 1 88 
 
 With cloudy or partly cloudy weather 89 
 
 Accumulation of error avoided 95 
 
 Velocity of wind, how estimated 34 
 
 Monthly maximum 35 
 
 Wind direction, how obtained, miles and direction, Form 1001 39 
 
 How recorded hourly on Form 1021 40 
 
 How recorded when 1 mile or less per hour 39, 40 
 
 How recorded calm 39 
 
 Wind direction points cleaned 14 
 
 Wind movement, how obtained, total by register 32 
 
 From noon to noon, by dial 33 
 
 Hourly, how recorded, Form 1022 38 
 
 Monthly, checked by dial readings 36 
 
 Wind velocities, perfect records, how obtained from triple, double, and single 
 
 registers 1 
 
 Wind velocity, current, from register, how obtained. 26 
 
 How obtained, current, from dial 31 
 
 Estimated 34 
 
 Maximum, from register, how obtained 27 
 
 Extreme, from register, how obtained 28 
 
 Maximum and extreme, how entered on Form 1017 30 
 
 Monthly maximum, how obtained 35 
 
 Caution against errors in maximum and extreme 50 
 
 Minute scales for 29 
 
 o 
 
Cornell University Library 
 QC 871.M39 
 
 Instructions for obtaining and transcrib 
 
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