STO ^^^^^^^^^^^^^^^^^^^^^^i^^^^"^^"^^ ^/- REESE LIBRARY. OF THK UNIVERSITY OF CALIFORNIA. Received 518 BROADWAY, (Opp. St. Nicholas Hotel.) NEW Yofl# MAGNETIC VARIATION IN THE UNITED STATES BEING A COMPILATION OF OBSERVATIONS MADE IN AMERICA FROM THE YEAR 1640 TO THE PRESENT DATE J TABULATED AND ARRANGED FOR THE USE OF SURVEYORS, WITH A BRIEF ACCOUNT OF THE NATURE OF TERRESTRIAL MAGNETISM, Its various theories as to the Origin, its Change in Intensity and Direction, and the progress of MAGNETIC OBSERV^Troil. OF THE UNIVEKSITY' J. B. STONE, Ph.B., C. E., Formerly instructor in Mathematics in the Sheffield Scientific School of Yale College. NEW YORK: i Entered according to Act of Congress, in the year 1878, ^//J/ in the Office of the Librarian of Congress at Washington, D. C. PRICE $1.50. ]. B. STONE, C.E., P. O. Box, 446, BOONTON, N. ]. SMITH & VANDEN HOUTEN, PRINTERS, 181 WILLIAM STREET, NEW YORK. PREFACE HAVING frequently been called upon to retrace property lines according to surveys of from twenty to eighty years ago, I was much surprised, by reference to the tables of my text-books, to find no means for answering almost the first question that would arise, viz. , what allowance must I make for the difference in variation ? In default of this information I must first asc rta'n if two adjacent known points can u ; found upon which line a t taring may be taken and compared with the original. If this cannot be done, then I must run, comparatively at random, until I reach a second known point, and from a plotting or calculation, both of my own work and the original, I may arrive at this difference a method involving con- siderable work. Upon inquiry as to what work to procure that I might gain this information, I was referred to various volumes of " Silliman's Jour- nal,'' ditto of "Transactions" of "Associations," and numerous records from the various departments of the Government. Some of these I was able to procure and others not. Fortunately I obtained sufficient to cover practically what was needed to accomplish the design of this work. The author lays no claim to originality whatever ; his object has been simply to make a compilation of the recorded facts in relation (iii.) PREFACE. to his subject having a practical bearing only, and of especial use in surveys by the compass for the recovery of old lines. He has not hesitated to copy liberally or literally from the published papers of the various departments of the Government wherever the matter or its presentation has pleased him, and the article on the methods of ascertaining the variation by observation with compass or theodolite is taken wholly from the Department "Instructions to the Surveyors General of Public Lands." The tables are compiled principally from the papers of the Coast Survey by Mr. Schott. A brief resume is given of the progress in the investigation of the subject of magnetic variation from the earliest periods of its discovery in England to the present time. The author has given as an example the method he used for reduc- ing the variation at adjacent points to that at his own place, and he recommends it as being simple and sufficiently accurate for the pur- pose required. He would respectfully recommend to each surveyor the compilation of a similar table for his own particular locality, from which, by inspection, the variation at any date may be known. To enable him to do this without the preliminary labor involved in the collecting and sifting from a disconnected mass of matter pub- lished on the subject the information desired, the author has compiled this little work, thinking that, though imperfect as it may be, it yet may meet a practical need that others beside himself have felt. TABLE OF CONTENTS. PAOH PREFACE < 6 PART I. DISCOVERY OP VARIATION AND DIP 11 RESEARCHES or HALLEY, HUMBOLDT AND Boss 11 TABLE OF VARIATION IN LONDON FROM 1576 TO 1865 12 CHANGE AND REVERSION OF CHANGE IN VARIATION 13 " MAGNETIC CRUSADE " F 1835 15 FIRST COMPILATION IN AMERICA 14 CAUSE OF TERRESTRIAL MAGNETISM 19 THEORIES OF MAYER, GAUSS, AMPERE AND NORTON 17 MAGNETIC STORMS Looms' CONCLUSIONS 19 MAGNETIC INTENSITY, REMARKS AND TABLE 21 ACCURACY OF SURVEYS BY THE COMPASS 22 LACK OF INFORMATION CONCERNING VARIATION IN TEXT BOOKS ON SURVEYING 23 METHOD OF ASCERTAINING VARIATION BY THEODOLITE AND COMPASS 28 FORMATION OF VARIATION TABLES OF ANY LOCALITY 33 AUTHORS METHOD OF INTERPOLATION 34 AUTHOR'S REQUEST FOR REPORTS OF OBSERVATIONS 37 PART II. DESCRIPTION OF TABLES 41 PART m. TABLES OF VARIATION, DIP AND INTENSITY 61 INDEX 131 (TO.) MAGNETIC VARIATION. HELLER & BRIGHTLY, Engineering & Surveying Instruments 33 N. SEVENTH ST., PHILA. Without decreasing size of any part of our "Engineers' Transit," we have reduced the weight one-half. An ordinary Transit Telescope magnifies from 10 to 12 diameters, our new Tran- sit Telescope (length 10)^ inches, shows objects erect and not inverted) magnifies 28 diameters and will read time on a watch-dial at 98H feet. For description of our new Mining Transit (weighl 6% Ibs.) and Plummet Lamp, see Van Nostrand's Engineering Magazine, June, Io73. Extract from report of Coinmitte of Civ. Engs. appointed by Franklin Inst. to examine H. & B.'s new Transit (Dec., 1871): "It exhibits several novelties of construction, which, in the opinion of the Committee, render it superior to those now in usa, and in its opinion the deviations which they have made from the common styles ot Transit are decided improvements." JOHN C. TEAUTWINE, Chairman. We have just (January 1878) placed on the tripods of our Surveying Instru- ments a patented improvement for instantaneously setting up and leveling, to which we would call the attention of those interested ; also to our new Transit Compass which combines the telescope accuracy of the Engineer's Transit, with the portability of the Surveyors' Compass. The attention of those Surveyors and Enpineers to whom a sensitive magnetic needle is of importance, is called to the magnetic needles attached to our make of in- struments. The steel of these needles is so selected as to obtain 1 he greatest amount of magnetism with the least weight; particular attention being given to the hardening, tempering and magnetizing. Attention is also called to an unsuspected cause ot error in magnetic readings from the material of the frames of which the ordinary hand magnifiers are made, these in a majority of cases having either magnetic attraction in themselves, orin the material being such that the least friction, such as carrying in the pockets, exciting the frame electrically. The ordinary hand magnifier for reading verniers and needle bearings, that has a vulcanite or hard rubber frame, is peculiarly liable to this electrical state, as the following simple experiment will show : Tear tissue paper or newspaper into small shreds, rub the frame of one of these hard rubber magnifiers briskly on the coat eleeve for a few moments, this friction will so electrify the frame that the paper will fly upward and stick to the frame, if the frame is held above them, or after reading a bearing rub the frame in the same manner, and approach the needle with it, when a diffwence of sometimes over half a de- gree will be noticed from tbe first reading. In consequence of these defects we are supplying to Engineers and Surveyors a magnifier free of these evils. For much valuable information respecting magnetic needles, defects of Surveying Compasses, see pamphlet published by us, entitled " Kemarks on Engineers' Surveying Instruments." This il'ustrated pamphlet of 100 pages will be sent to any address, post-paid, on receipts of 10 cents ia stamps. I, MAGNETIC VARIATION. SINCE the first discovery of Terrestrial Magnetism its variability in direction and intensity has been the subject of much research and observation. The first to point out the divergence of the magnetic needle from the true north point, and that it was different at different points, was the English philosopher, Gilbert, who also maintained that it was constant for the same place. The change in variation in proceeding from place to place was hardly known, though it had been noticed and marked on an atlas by Andreas Bianco, in 1436, and its discovery was one of the most serious causes for alarm to the companions of Columbus on his voyage of discovery in 1492. Owing to primitive needles being floated in basins of water, and to crudeness in manufacture of those first suspended, the dip of the needle was not discovered until the year 1576. From the time the difference of the variation of the needle became universally recognized, it was especially important to mariners to register the variation in all points of the world. During the reign of William and Mary the astronomer Halley was appointed to the command of a ship in the Royal Navy with instructions ' ' to seek by observation the discovery of the rule for the variation of the compass." He published " Magnetic Charts" as the result of his investigations, which were afterward revised and corrected. Humboldt also gave the subject much attention and collected many observations. All these observations seemed to indicate a magnetic pole below the surface of the earth at some point north-west of Hudson Bay, and Captain Ross on his second voyage is supposed to have reached it, in latitude N. 70 53' and longitude west from Greenwich 95 45' -8, the dipping needle there 12 MAGNETIC VARIATION. pointing vertically downward and the variation compass turning toward this point when placed at points adjacent. The earlier observations could not have been very close or connected, as the variation at London was supposed to be constant until the year 1633 when Gillebrand discov- ered that it had receded from n east in 1580, to 4 east. Since that time in Europe, the needle has been slowly turning westward until the year 1815 when it reached its maximum westerly deflection, then it began slowly to turn eastward again. The following table exhibits the progressive changes ob- served in London from 1576 to 1865 : YEAR. OBSERVER. VARIATION. I' 1662 >- No variation. 1666.. o 14 W 1670 26" 1700 940 1720 13 o 1740 16 IQ 1760 iq *?o 1774 22 2O 1778 22 II 1790 23 30 1800 o jy 24 16 1806 . 24 8 1813.. Col. Beaufort 24 20 1815 ... . do 24 27 (Max.) 1816 24 17 1820 24 ii 182^.. 24 10 1831 . 24 o 1865.. 21 MAGNETIC VARIATION. The dip was found also to be a variable angle, differing at different places, as the following table exhibits from observations made at London : YEAR. OBSERVER. 1720 Graham.. 1773 Heberden 1780 Gilpin 1790 i " .-. 1800 1 " ... 1818 Kater.... 1821 Sabine . . . 1828 ; " ... 1830 I " ... 1863.. ANGLE OF DIP. 74 72 72 70 70 6^ 53 35 34 3 47 From which we observe that while the variation in dec- lination underwent a reversion in 1815, the variation in dip has been constantly diminishing by a rate compara- tively uniform. The variation at one place is but a poor guide for the variation at others more or less remote. While the variation at London was undergoing the changes recorded above, in America, as recorded at Que- bec, Canada, the needle reached a westerly maximum in 1660, and then began turning easterly, until about the year 1 800. When, according to the record, at New York City, it reached an easterly maximum, and from that date again reversed its motion and began turning Westward, which is the direction of its present motion. The varia- tion and periods of reversion at other places were different, but at present the needle has a westerly motion through- out the entire United States and Canadas, except at the Pacific Coast Sometimes there is a marked difference in deflection, even though the places are comparatively near each other. Again there are particular parts of the earth's surface, as 14 NAGNETIC VARIATION. in the Western part of the Antilles, and in Spitzenberg, where the means declination of the needle has scarcely undergone any sensible change in the course of the last hundred years, and sinceji66o the needle has been per- manent in the Island of Jamaica, of which Sir John Hers- chel remarks in Cosmos, Sabine's Translation, vol. I, p. 419. "The whole mass of West India property has been / saved from the bottomless pit of endless litigation, by the ' invariability of the magnetic declination in Jamaica and the surrounding archipelago, as during the whole of the last century all surveys of property were conducted solely by the compass. " | Another important fact was discovered in 1724, by Mr. Graham, a philosophical instrument maker of London, viz. : that there was also a small diurnal motion of the needle. This daily variation was established by 1,000 observations, and afterward confirmed by 4,000 more made by Canton. It appeared also by Canton's researches that the diurnal variation undergoes an annual change, being greatest in summer, or about one-quarter of a degree, while in winter it is but one-half that quantity. The subject of magnetic variation did not receive general attention in Europe until about the year 1835, when at the instance of Baron Von Humboldt, a magnetic crusade was organized and numerous observations were establish- ed, by the various governments and philosophical societies, at many and distant parts of the world, and a systematic method of daily observations instituted. The facts observed at each station were the intensity of the magnetic force, the declination of the needle from the true meridian, or variation, and the inclination to the horizon, or dip. Those established in America were, at Toronto, Cam- bridge, Philadelphia and Washington. In addition to these, were the observations made by the several Arctic and Antarctic exploring expeditions. The whole was also discussed by Professor Lloyd, of Dublin, MAGNETIC VARIATION. 15 and Col. Sabine, director of the observatory at Toronto, Canada, and their results exhibited in the ' ' Philosophical Transactions of the British Association" for 1843. From these observations magnetic charts were published, showing the curves of equal variation and dip, also the magnetic equator, or curve of no dip. One has recently been published by the British govern- ment, from its magnetic surveys of i855-'yo. From its inspection we note the singularity of some of its curves of equal variation. %First, the main line of no variation passes from the N. magnetic pole at lat. 70 N., long. 95 W. to the N. E. shore of Lake Superior ; thence to near Wheeling, W. Va. ; thence S. E. to the mouth of the Amazon ; thence S. through South Americi, reaching the Atlantic coast a little west of Rio Janeiro ; thence S. 20 + E. to the S. magnetic pole. From the polar regions, where we lose sight of it, it emerges in lat. 70 S., long. 138 E., and proceeds north through Australia, where it bends to the west, running N. of W., crossing the equator at long. 75 E., thence proceeding N. 30+ W., touching the west shore of the Caspian Sea, passing about 4 east of St. Petersburgh, and out of sight at lat 70 N., long. 31 E. There is also another curve of no variation, elliptical in form, about which lines of variation to the extent of from 5 to 8 circulate entirely, others partly, and then proceed towards the magnetic poles. This ellipse has its major axis on the meridian 130 E., and extends from lat. 15 N. to 68 N., while its minor axis extends from 108 to 151 E. long. Within, this immense ellipse of no variation, parallel isogenic curves of W. variation circulate to the limit of 6 variation. Without, all the curves of E variation running from the N. to the S. magnetic poles embrace it, except the curve i variation. In the Pacific Ocean, at a point in lat 1 1 N. , long. 1 6 MAGNETIC VARIATION. 06 W., the line of 8 variation makes a lov.p, extending from lat. 17 N. to 25 S., and to long. 171 W. Within this the curves of 7, 6, and 5 E. variation circulate in elliptical form. The latter has its major axis on the equator, and extends from long. 120 to 149 W., its minor axis being 13 in length. COMPILATION OF MAGNETIC OBSERVATIONS. The first effort made towards a compilation of obesrva- tions in America, was in the year 1835, by Professor Loomis of Yale College, then of Western Reserve College. He, in the name, of the "Connecticut Academy of Arts and Sciences," wrote a great number of letters asking re- sults of observations, to which answers were generally received. These observations he compiled and published in Sullivan's Journal, "Vol. XXXIV., 1838. Additional compilations were made by him and pub- lished in Vols. XXXIX. and XL. ; and in a discussion published in Vol. XLIIL, these observations were re- duced to the epoch of 1840, and the annual motion com- puted for that period. A combination of these form Table 7. Concerning which he remarks : ' ' From an attentive examination of this table, it will be seen that from the time of the earliest observations down to about the com- mencement of the present century, the westerly variation was decreasing, and the easterly increasing in every part of the United States ; that more recently the reverse has taken place ; that is, thatx a retrogade movement of the needle has commenced. The precise year when this change took place cannot be certainly known. To determine this we need more numerous and more accurate observations. All the observations, however, agree in this, that the change began as early as 1819, while the Philadelphia observations make it as early as 1793, and those at Newbern, N. C, not far from the same year. The annual motion is much greater in the Eastern States than in the east and west. 1 have carefully compared all the MAGNETIC VARIATION. I/ observations contained in the preceding table, and without giving the particulars of this discussion, will state at once the conclusion at which I have arrived, viz. : that the westerly variation is at present increasing, and the easterly diminishing in every part of the United States ; that thij change commenced between the years 1793 an ^ J 8i9, probably not everywhere simultaneously ; and that the present annual change of variation is about "2' in the Southern and Western States ; from 3' to 4' in the Middle States ; and from 5' to 7' in the New England States." In the same number were published tables of dip ob- servations, which are given in Table 5 of this work. The effort to discover a specific law governing magnetic variation has not been as productive of definite results as was hoped for, the evidence tending to show that, what- ever the general law may be, it is so modified by local or other influences, that, as M. Duperry remarks in (Annales de Chimie, 1830,) "We are led by the phenomenon of the dip, as well as the variation, to conclude that every place has its own magnetic axis, with its own pole and its own equator." CAUSE OF TERRESTRIAL MAGNETISM. > Numerous theories have been advanced as to the cause of terrestrial magnetism. Among the first was that of Dr. Mayer about the middle of the last century, which was that the earth contained a huge single magnet near its centre, with its axis passing through the earth's centre at right angles with the magnetic equator. Both Humboldt and Biot independently adopted this theory. The next hypothesis of any importance was advanced by Hansteen, of Norway. He substituted two magnets ex- ccntrically arranged, and of unequal power. In 1838 Gauss published his celebrated memoir on ter- restrial magnetism. He regards the earth as an infinite assemblage of magnets, or in effect the whole earth as a magnet, [e determined certain relatipns between the 1 8 MAGNETIC VARIATION. components of these magnetic forces, and expressed these components by general formulas, the constants of which can be obtained by observation. He showed that only two poles can exist. Gauss compared the results reached by his calculations with accurate observation made at 91 magnetic stations. In a majority of cases the difference between calculation and observation was about equal to the errors of observa- tion, and frequently not greater than those made by practised observers at the same station. His calculated position for the north pole was within i of the point observed by Captain Ross, and his calculated intensity at the poles was N. 1,701, S. 2.253. His theory involved the idea of two magnetic fluids giv- ing magnetic polarity to each terrestrial particle, or, in other words, of a repulsive and attractive force acting in- versely at the square of the distance. No change need be involved in this by the adoption of the later theory of Am- pere, viz., that the northernly and southernly magnetic currents are due to easterly and westerly electric currents; thus transforming the earth into an immense electro mag- net. Professor W. A. Norton, of the Sheffield Scientific School of Yale College, in his papers on the subject of " Mole- cular Physics, '' adopting the theory of Ampere, proposes a theory as to the causes of these electric currents, based upon his theory of the constitution of the ultimate atom of matter, as follows, viz. : That they are due primarily to the impact of the ether of terrestrial matter upon the ether of space, and that the diurnal motion of the needle is mainly due to the difference in the force of impact of that part of the earth opposite to the sun to that part adjacent; the im- pact of the former being due to the sum of the earth's yearly and daily motion, while in the latter instance it is due to the difference only, of these two motions.* *In a recent conversation Professor Norton remarked that the re- sults of later observations and discussions had verified his theory in numerous instances of detail, and that he was now more than ever confident of its correctness, MAGNETIC VARIATION. 19 In addition to the regular diurnal and monthly changes, the needle is liable to sudden and violent perturbation or magnetic storms. These are always accompanied by au- rora and electric disturbances, and occur simultaneously over the whole earth. It is the general opinion of mag- neticians that the sun is the agent causing the disturbances. The wonderful coincidence of the eleven years' period- icity of the maximum of sun spots and the maximum of perturbations, together with the simultaneous agitation of the sun's photosphere with that of the magnetic needle, as observed by Professor Schwabe, of Dessau, for over forty years, scarcely leave a doubt of it. ' ' There is some reason, " observes Balfour Stewart (Proceedings of Royal Inst. , vol. iv. ), "to believe that on one occasion our lu- minary was caught in the very act. On the* ist of De- cember, 1859, two astronomers (Messrs. Carrington and Hodgson) were independently observing the sun's disc, which exhibited at that time a very bright spot, when about a quarter past eleven they noticed a bright star of light suddenly break out over the spot and move with great velocity across the sun's surface. On Mr. Carrington referring afterward to Kew Observa- tory, at which place the position of the magnet is recorded continuously by photography, it was found that a magnetic disturbance had broken out at the very moment when this singular appearance had been observed. Professor Loomis, in a paper concerning the causes of diurnal variation, published in ("American Journal Science, Vol. L. , 1870,") arrives at the following con- clusions : (i.) A diurnal inequality of the magnetic declination, amounting at Prague to about six minutes, is independent of the changes in the sun's surface from year to year. (2.) The excess of the diurnal inequality above six minutes, as observed at Prague, is almost exactly propor- tional to the amount of spotted surface upon the sun, and may, therefore, be, inferred to be produced by this disturb-* 2O MAGNETIC VARIATION. ance of the sun's surface, or both disturbances may be re- ferred to a common cause. (3.) Great disturbances of the earth's magnetism are ac- companied by unusual disturbances of the sun's surface on the very day of the magnetic storm ; and are therefore due to some influence which emanates immediately. (4.) The great disturbance of the sun's surface which accompanies a terrestrial magnetic storm is generally heralded by a smaller disturbance three or four days pre- vious, succeeded by a comparative calm which immediately precedes the magnetic storm. ' MAGNETIC VARIATION. 21 INTENSITY OF TERESTRIAL MAGNETISM. The magnetic intensity at any point of the globe may be determined by observation on the times of vibration of a dipping needle ; the dipping needle holding to terrestrial magnetism the same relation that a pendulum holds to gravitation. In a state of rest both show the directions of the resultants of these forces, and if set in vibration we can, from the number of these vibrations in a given time, determine the intensity of the vibrating force at the various points by assuming one of them to be unity. The inten- sity was found to be proportional to the square of the num- ber of vibrations X by the cos of the dip or F = n' x cos d. The following table exhibits the ratio of intensity for the various places and dates, the unit being a point of minimum intensity as observed by Humboldt in Southern Peru in 1798 : PLACES OF OBSERVATION. YEAR. LATITUDE N. MAGNETIC INTENSITY. St. Antonio 1802 O O' I,087 Ga.rtha.gena. . 1801 IO 2C I,2O4 New York 1822 4O 47 1,003 Naples 180; 40 co 1,274 Lyons . * * * * 180; AC 46 I Wl Paris 1800 48 C2 1,148 Brussels . . 1820 CJO C2 I, -247 Berlin 1829 t?2 t;i O^ aperture in a board, and held at some JR6-M p-*-* ^^/ distance by an assistant, is then moved according to signals, until jt is covered by the intersection of the spider's lines. A picket driven into the ground, under the light, serves to mark the meridian line for reference by day, when the angle formed by it and the magnetic meridian may be measured, MAGNETIC VARIATION. 33 Having determined the present variation, to ascertain the variation in times past, the tables which follow have been collected and compiled as remarked in the preface. Although hardly of definite value for the object aimed at in- this work, the angle of ' ' dip " is also given in some of the tables. The same remark may be made concerning the intensity of the magnetic force. A brief description of each table is given further on. As remarked in the preface, the author recommends to each surveyor the. compiling of a table of variations for each decade, and as far back as the records of adjacent places will allow. Tables "A," "B" and "C" were compiled by the author to enable him to form such a table for his own locality. His method of doing so is given, not, perhaps, as the best, but as giving results sufficiently accurate for the purpose intended, and as a guide for similar reductions by others. The convenience and use for such a table will be appreciated by every surveyor. The first point to be determined is the latitude and longitude. This may be ascertained by the given methods of observation, but as these involve the use of more accurate instruments than most surveyors possess, it may be ob- tained with sufficient accuracy by inspection from any reliable county map. A table may then be made similar to table ."A," con- taining the latitude and longitude of the adjacent points where there are recorded observations. From this construct a map or plotting, as given page 35, on a conveniently large scale, showing the relative position of these points. Connect these by lines which shall pass near the point in question, and note the points where these cross lines at right angles drawn through this point, as the points i, 2, 3, &c. A table similar to table "B" may then be made showing the comparative distances to the various points as measured by scaling. The ratio the distances to the various points i, 2, &c, bear to the total distance from place to place is calculated, also the ratio of the distance i to Boonton, i to 3, &c., as shown in the 34 MAGNETIC VARIATION. column marked " ratio." We have now the data for com- puting the variation at the point required. First tabulate, as in table " C," the variations for the points used in the computation, dating back as far as data may be found. From this a table similar to the second part of table "C " may be computed showing the variation at the points i, 2, 3, &c., for the various years ; thus, taking the point I on the line from New York to Buffalo, the distance from New York to i is 9 per cent, of the distance from New York to Buffalo. The difference of variation between the two locations for the year 1850 is 6. 34' 2. 05' = 4. 29 degrees. Nine per cent of this difference subtracted from the variation of New York gives (6.34 o3o) 5.95 degrees as the variation at the point i for 1850. This is based upon the principle that the variation at points between the two known points is in direct proportion as the distance, which is not strictly true; but as the known points are comparatively near each other, the results thus obtained may be taken as sufficiently accurate for practical purposes. Having computed in a similar manner the variation of the various points 1 , 2, 3, &c. , and tabulated them for con- venience, the variation at Boonton is computed from them by the same principle of proportion, and the mean of these values gives the true variation. Thus, taking the year 1850, the difference of the variation between 2 and 4 is 6. 48 5. 42 = i.o6. This multiplied by 0.33, the ratio of the distance 2 to Boonton divided by the distance 2 to 4, gives (1.06X0.33) = o.35, and this added to 5. 4 2 the variation at 2 gives 5. 77 as the variation at Boonton for 1850. In a similar manner, by combining 1-3 and 5-6, the values 5. 9 5 and 5. 96 were obtained. The mean of these gives 5. 89 as the variation for Boon- ton for the year 1850. Computing, thus, the variation for each decade and the ratio of annual motion, we are enabled at once to obtain MAGNETIC VARIATION. 35 40 41 42 Latitude North. 43 41 42 ^ MAGNETIC VARIATION. the proper allowance to be made for the difference of vari- ation between any two dates within the i9th century. If additional data can be obtained that is reliable and especially at adjacent points they should be added to the tables. If this computation is made from Table 27 alone it should be compared with the records found in the various other tables for adjacent points, which may be obtained by ref- erence to the general index by States. It would be advisable to copy the results of this compu- tation in the fielcf book, as this information would thus always be at hand'just when and where it is needed. It is of importance that every surveyor should observe carefully several times each year the magnetic variation that he may verify his tables and also note on his surveys the variation as actually observed. This may easily be done ; for having once carefully measured the angle any convenient line makes with the true meridian, the magnetic bearing of this line taken from time to time gives all the data required. If this rule had been adhered to by earlier surveyors, much embarrassment and labor would have been saved and the need of this present work had never been felt It may be remarked here, that after the table shall be thus computed, upon comparison with observation it may be found to differ. This does not impair its usefulness as the information sought is not so much the actual variation as the difference in variation at the various periods. As before remarked the difference in the variation at different points in the same line, is not exactly proportional as their respective distances ; yet the change from year to year is, or very nearly so. As it is the author's purpose at some future day to re- vise and extend this work, he closes w>tb this request to each surveyor, into whose hands it may lail, viz, that he will send to him the results of whatever observations of magnetic variation he may have previously made, and that from time to time observations be taken as often as MAGNETIC VARIATION. 37 once or twice a year and if convenient between the hours of 10 o'clock A. M. and noon, the mean variation for the day being indicated about that time. The results forwarded should declare : ist The latitude and longitude of the place of observa- tion. 2d. The variation, giving date and time of observa- tion. 3d. Nature of the locality of observation and wether lia- ble to any local disturbance. 4th. Kind of instrument used in the observation and in fixing the meridian line. This may easily be done, if a true meridian line is once established at some convenient point, or a line making a known angle with the true meridian. Let these observations be made as accurately as possible, or better, let a number be taken and their mean result be forwarded. By this means a vast amount of statistics may be collected of great value in years to come. Please ad- dress them to the author at Boonton, N. J., with the \\ords ' ' magnetic variation " written on the lower left hand corner of the envelope, in order that they may be proper- ly filed if received in his absence. II. MAGNETIC VARIATION. 41 DESCRIPTION OF TABLES. Tables "A," "B," and "C" were compiled by the author to enable him to compute and tabulate > the decen- nial variation for the city of Boonton, N. J. Table i, page 54, is a record of declination observed at Washington, D. C., for the years i86y-'68, and '69, by Mr. Schott, of the Coast Survey, and shows the annual change in variation at that period and locality, "-Me Table 2, page 54, shows the simultaneous changes in the dip. In reference to this latter table, Mr. Schott remarks : "The present (1869) mean annual decrease in dip is 4. 7 minutes. " This diminution of the dip is in accordance with the observations at Toronto, Canada, where the dip increased up to 1859, and has since been steadily decreasing. At Eastport, Maine, the dip was observed to be diminishing during the period 1860-^64 ; at Key West, Florida, the observations between 1860 and 1866 indicate a diminu- tion. It appears from previous records that the dip at- tained a minimum about 1842 on our Atlantic coast; from that time to about 1859, it was on the increase, when it unexpectedly reversed its motion and commenced again to diminish ; possibly this increase during about seventeen years was only the effect of a secondary wave, masking for that time the general effect, which was de- creasing the dip. Table 3, page 55, illustrates the changes in declination during the day for the years i867~'68, and '69. The times of eastern and western elongation, the hour of aver- erage variation, and the mean diurnal range for the various months, are given in their respective columns. By inspection of this table, we find the period of great- est range to be during the summer months, and that throughout the year, the time for obtaining the average of 4* MAGNETIC VARIATION. the daily variation is between the hours of 10 and n o'clock, A. M. Table 4, page 56, is a record of the dip as observed in the District of Columbia from the year 1839 to 1869, and Table 5, page 57, is a copy of dip observations throughout the United States, and published by Professor Loomis in Silliman's Journal, Vol. 34, 1838. Table 6, page 59, is Professor Loomis' famous collection, published as above in 1838, and, as before mentioned, was the first general collection made in the United States. The author has added to it somewhat from his later col- lections, published in 1840. Table 7, page 68, is a later collection by Professor Loomis, and published by him in 1842. These observa- tions were discussed by him, their annual motions compu- ted, and the variation reduced to the year 1 840. Table 8, page 75, is a collection published by Professor Bache, Superintendent of the Coast Survey, in the Ameri- can Journal of Science, Vol. 24, 1857. It is a compila- tion of observations made by the United States Coast Sur- vey, which Professor Bache discusses in a lengthly article, and makes a reduction of both variation and dip to the year 1850. These observations are principally at points along the coast, of which they give a very full record. In the same article were a few observations compiled from various sources, and some communicated from Mexico to the Smithsonian Institute by Messrs. Mueller and Sonntag; these form tables 9 and 10. Table n, page 83, is taken from the U. S. Coast Sur- vey reports for 1874 to which the author has added the colums showing the annual change for the years 1840, 50 and 60. Concerning this table, Mr. Schott rerrarks : ' ' This table shows the number of observations at each place ; the apparent probable error of one observation (in- MAGNETIC VARIATION. 43 eluding errors arising from want of identity of stations and from instrumental defects, ) expressed in minutes of arc ; the computed epoch of greatest easterly deflection in the secular motion, together with the amount and direction of the declination of that epoch ; and the computed an- nual changes at the epochs 1870 and 1880, expressed in minutes. The probable errors given above will serve to convey some rude idea of the relative value of each series of ob- servations. The imperfections in the instrumental means of the older observations in many cases react unfavorably on the modern observations made with more precise in- struments ; the observations, for instance, taken by Hud- son in 1 609, in the vicinity of New York Bay, are fairly chargeable with a proper error of 3 -f (a single result); those taken by Vancouver on our western coast, between 1792 and 1794, are subject to a probable uncertainty of -f i (each). Increased precision was obtained with the im- provement of the azimuth compass and the allowance for disturbing effect of the ship's iron, and, for shore stations, with the introduction of the theodolite for determining the astronomical meridian. A cursory examination of the column containing the epochs of greatest easterly excursion, the deflecting force producing the secular change attaining then an easterly maximum, shows that the needle became stationary in direction, and then reversed its secular motion, in the New England States toward the end of the past century, in the Atlantic coast States to the west and south early in the present, and in Mexico about the close of the first third of the present century. In California, Oregon and Wash- ington Territory, it has not yet reached this condition. We thus have the following epochs for comparison : Hal- ifax, about 1711 ; Portland, Portsmouth, Newburyport, Salem, Boston, Cambridge, Nantucket and Providence, about 1779; Hartford, New Haven, New York, Hartbor- ough, Philadelphia, Washington and Cape Henry, about 1800; Charleston, Savannah, Key West and Havana, 44 MAGNETIC VARIATION. about 1 800; New Orleans, about 1831; Vera Cruz, Mexico, Acapulo and San Bias, about 1837 ; San Diego, Monterey and San Francisco, expected about 1 907 (yet very uncertain). We are thus directed to the extreme northeastern States for probable indications of what may be expected to follow on the seaboard in more southern and western States. Respecting the secular movement of the needle, apparent- ly a little more than a century passed before the influence which produced the turning of the north end of t*ie needle westward in Maine (increasing there the western declina- tion) was felt in Lower California (diminishing there the eastern declination). In California, Oregon and Wash- ington Territory, the eastern declination is at present still increasing, but with a losing rate. By the time the west- ern elongation of the secular change is reached in Maine, we may expect to see the needle in the opposite phase, or at its eastern elongation in California. We cannot as yet fol- low this influence directly over the interior of the United States for want of early observations ; the westernmost in- terior stations for which an epoch could be made out were Buffalo, Erie, Cleveland and Detroit; these give the average turning epoch 1794. It may be quite practicable hereafter to trace out curves uniting all stations where the needle was stationary at a given epoch, and again at other epochs for regular intervals of time, say of ten or twenty- five years. " Table 12, page 87, is compiled from observations by the Coast Survey and reduced to the year 1860 by Mr. Schott. Table 13, page 89, is also a compilation of Mr. Schott, from observations in the western coast. Table 14, page 90, is by the same, from observations by the Coast Survey. Table 15, page 93, is compiled from the observation of Prof. A. D. Bache in his magnetic survey of Pennsylvania in 1840-1, and with it are Combined some observations by MAGNETIC VARIATION. Mr. Schott within the same limit in 1862, from a com- parison of which the annual change may be obtained. Table 1 6, page 94, gives the position of the points of curves whose variation is respectively o, 2 and 4 ; also of curves where the dip is respectively 71, 72, 73, 74 and 75, as computed by Prof. Bache. Table 17, page 95, is from the report of Captain John Pope, U. S. A. , upon his exploration for a Pacific Railway route. Table 18, page 96, is taken from the report of Captain John Mullan, U. S. A. , from observation made while con- ducting a survey for a military road from Fort Walla- Walla to Fort Bentori between the years 1858 62. There are no dates given to his observations, and I have assigned them the date of 1860. Table 19, page 97, is compiled from the report of Captain J. H. Simpson, U. S. A., upon his exploration between Fort Leaven worth and Carson Valley, Nevada, in the years 1858-9. Table 20, page 98, contains the observations for declin- ation and dip, made by Lieut. Whipple and party upon their exploration of the 35th parallel in 1853-4. Table 21, page 101, gives the declination observed upon the Mexican boundary survey, by Major Wm. H. Emory, U. S. A. The table gives also the declinations determined on previous surveys upon the same boundary, with a few borrowed from the Coast Survey reports. These are in- troduced as affording important elements in Major Emory's discussion. From these observations he determines a formula for computing the declinations at assumed points by which he constructs the next following table. The re- sults from his formula, when applied to the points of observation, agree very closely except at Presidio del Norte, Copper Mines and Mouth of Canon, the first two being in excess of the observed declination 37' and 56', while at the latter station it is 33' less. Table 22, page 102, is computed from the observations in the preceding table by Emory's formula. It gives the 46 MAGNETIC VARIATION. latitude and longitude of the points of equal variation, the amount of variation being given at the top of each column. Table 23, page 103, is compiled from the records of Lieut. G. M. Wheeler's exploration party. Table 24, page 104, is compiled from observations made upon the surveys of the North and North-west lakes, under the direction of Gen. C. B. Comstock, U. S. A. Table 25, page 105, is a condensed form of one of the most valuable and extensive compilations ever made in America. It is the work of Mr. Schott, and published by him in the Coast Survey report for 1874. It embraces observations over an extended period and at widely separated points, dating as far back as the early French settlement of Quebec in 1649, the times of the Pil- grims at Boston and Cambridge 1700 and 1708, and the early Dutch at New York in 1680. Hendrick Hudson, on his third voyage in 1609, made several observations near the mouth of the Hudson River, but as these results vary from 2 to 13, they have not been used. At Philadelphia observations were recorded as early as 1701, and at Kingston, Jamaica, as early as 1660. This latter observation, however, is not used. The earliest at New Orleans is by Father Laval in 1720, while on the Pacific coast. Several are recorded by Van Couver in 1792, and in Mexico one is recorded by Anson in 1744. Of the great mass of observations condensed in this table, those subsequent to the year 1845 were principally made under the direction of the United States Coast Survey. Those of prior date were collected and compiled from various reliable sources, such as communications from eminent surveyors and physicists, the records at the various college observatories, reports of explorers, and records of public surveys. The fourth column, marked "computed," gives the variation as calculated from the impirical formulas ob- tained by Mr. Schott for each particular locality, as given in Table 26, page 120. They are thus placed in apposition to the observed MAGNETIC VARIATION. 4/ variation that their exceedingly close approximation may be shown, thus attesting the faithfulness and success of Mr. Schott's efforts in formulating. The last eleven stations were not included in his dis- cussion. Table 26, page 120, as above mentioned, are the impirical formulas obtained by Mr. Schott for calculating the varia- tion at any date. The letter " m " in the formulas represents the number of years and fractions of a year prior or subsequent to Jan. ist, 1850. If "t" represents the year and fraction of a year whose variation is required then m = t 1850. Table 27, page 122, shows the decennial value of the variation, and was computed by the formulas of Table 26. Mr. Schott remarks concerning it as follows : These tables have been constructed to facilitate the re- duction of observed declinations from one epoch to an- other ; they will be found specially useful when old lines, run by compass, have to be retraced, and for the construc- tion of isogonic charts for a given epoch. Blanks occurring in the table indicate no or doubtful values for the corresponding times. Values given to the nearest tenth of a degree are less reliable than those given to hundredths. A -(- sign indicates west, a sign east declination. PA.RT III MAGNETIC VARIATION. $ TABLES. DIRECTIONS FOR THEIR USE. On page 131, will be found an index alphabetically arran- ged according to the various States and territories. In consulting these tables for the variation of any point, this index will designate the table and page where obser- vations for that point may be found ; also of adjacent localities. Having made a compilation of all the data obtainable for that locality, it should be tabulated and dealt with as described on page 34,, part i. Longitude is measured west from Greenwich, and lati- tude is north throughout TABLES "A" AND "B." For Computing the Magnetic Variation at Boonton, N.J. TABLE "A." Locality. Latitude. Longitude. Boonton, N. J O ' 40 ?5 ' 74 26 New York 40 41 74 oo Albany 42 39 73 46 Buffalo 42 si 78 53.5 Philadelphia 30 C7 75 OQ Oxford. . , 42 26.5 75 40.S MAGNETIC VARIATION. TABLE "B." Comparative Distances. New York to % w York to New York to Philadelphia to Boonton 2 3 35 Boonton 23 * New York to New York to fi Boonton 5 } 7 28f Ratio. 0.09 0.26 o.io 0.36 0.06 o-33 O.IO 0.12 0.18 MAGNETIC VARIATION. 53 TABLE "C" For Computing the Magnetic Variation at Boonton > N. J. VARIATION. Locality . . . 1800. 1810. 1820. 1830. 1840. i 1850. 1860. 1870. 1880. N. Y. City.. Albany 4.28 430 C.4O o 447 c.7q o 4.91 6. 12 o 5-59 6.07 000 6.34 6.96 1 7.43 7.7O 8.47 Q. 2O o 7.84 Q.QO Buffalo Philadelpi'a Oxford .... 0.01 2.10 2.06 0.05 2.10 3.10 0.30 2.28 3-40 0.74 2.71 3-87 1-33 3-33 4.46 2.05 2.85 3 .68 4.II 4.99 5.89 5.14 5-89.6.65 y.yw 449 6.76 7.38 VARIATION DEDUCED FROM ABOVE. I .... 80 3- Q2 4. *"? C.2I t.OC 6 CQ 7 OQ 7 54 2 6 v t l6 4.0^ J.66 5.42 6.24 7. 10 7.QI 5.04 5.QQ 4. IQ f O 4.O4 6.03 6 68 i 7.2^ 7 72 4 . . 4.41 *r *y 4.60 p y- 6.48 7.11 7,61 8.0i; e . . _ Of -188 4.OC 4.40 P 16 6.55 ' 7.06 7.O? 1 :;;:;:::: 4.12 j.ww 4.16 4-34 4-79 5-45 6.20 6-83 7.34 7.78 VARIATION AT BOONTON DEDUCED FROM ABOVE. Boonton 1-3 3.8 9 3-92 4.10 4-54 5-22 5-95 6.60 7.10 7-55 2-4 (est. ) 5-6 Boonton av. 3-64 3-90 3.81 3.67 3-93 3-84 3-90 4.10 4-03 4-37 4.54 4.48 5.02 5-2i S'lS 5-77 5.96 5.89 6% 6.58 7.27 7- 7.16 7.96 7-55 7.69 Boonton Deg. & min 349 350 402 429 509 553 635 710 741 An. Motion. 0.18 1.14 2.70 4.02 4-44 4.19 3.36 3-i8 54 MAGNETIC VARIATION. TABLE I. Observed declination on Capitol Hill, Washington, D. C. MONTH. 1867. 1868. 1869. ANNUAL CHANGE. 1868-7. 1869-8. January O ' 2 4 6. 5 W. 47-9 43-3 46.4 51-3 496 46.4 47-7 50.0 49-5 50.1 48.2 O ' 2 4 8.7W. 49.0 47-3 5i-4 53-3 53-i 50.8 5i-7 52.7 52-3 52.2 52.2 ' 2 5 2. 3 W. ~5M 537 52-4 5 1 - 1 53-8W. +2.2 + I.I +4.0 +5-o +2.2 +3-5 +4-4 +4.0 +2.7 +2.8 +2.1 +4.0 +3-6 2 '9 +6.4 + 10 +0.8 +0.7 111 8"rt''5 . 113$ February March r'l June July August September October November Mean 248.IW. 2 5I.2W. TABLE II. Monthly changes in Magnetic Dip, observed at Capitol Hill, Washington, D. C. MONTH. 1867. ! 1868. 1869. ANNUAL CHANGE. 1867-8. 1868-9. January O ' 71 00.9 09-5 10.7 II. I 06.9 04.6 05.5 04.2 08.6 06.2 03.7 70 58.7 71 06.7 05.9 02.8 05-9 05.5 02.6 01.3 02.1 7 59- * 57-7 70 58 58.2 58.7 57-3 54-0 56.0 4-2 4.2 7-9 5-2 1.4 +0.1 1.6 7-3 -4.1 4.6 I.O -8.7 7.1 4.1 8.6 -1:1 111-? g'-o J a .a ja.iiua.iy rebruary March April May Tune Tulv August September October November December Mean 71 06.7 7i 03-4 MAGNETIC VARIATION. 55 TABLE III. Observed diurnal range of variation at Capitol Hill, Washington, D. C. MONTH. Meantime of Eastern Elongation, 1867, 1868, 1869. f* Ti- "^ SOD _. ~ ni *~ Time of Average Variation. 1 *3 II P Jan. H. M. 8 14. H. M. 21 H. M. IO CO 6 o Feb 8 li 3 1W iV IO C4. w.y 7e March April.. 8 17 7 CC 3 3 8 *** j*f 10 55 IO /17 j 93 II i May / .O 7 22 O 21 IO 22 ii 8 June 7 46 12 IO 7O 10 6 July . . 6 56 O1 IO OO 12 2 Aucr 7IO O 1Q IO OC ir o Sept Oct. 7 H * DV II 23 10 22 IO CI *O - v 12-5 IO 4. Nov .. 8 10 o c8 iw 51 IO 74. 7 -i Dec.. 8 12 i ii IO 4.2 66 Mean time of Reversion. April to September, inclusive, at. April to September, inclusive, at, On the average for the year and i h. and 17 m. p. m. October to March, inclusive, at. . . October to March, inclusive, at. . , H. M. 7 27 a. m. I 14 p.m. 7 5* 8 15 a. m. I 20 p.m. MAGNETIC VARIATION. TABLE IV. Record of Magnetic Dip observed in District of Colum- bia from 1839 to 1869. No. I 2 3 4 5 6 7 8 9 10 ii 12 '3 14 11 17 18 J9 20 21 22 Year. I. Observer. Locality. 1839.1 1841.0 1842.5 1844.4 1845-3 I85I-5 1852.4 1853-4 1855.7 1856.6 1857.2 1858.4 1859-5 1860.6 1861.6 1862.6 1863.5 1865.5 1866.8 1867.5 1868.5 1869.3 [7i 17-5] 18-3 13-5 16.4 [7i 33-9] 18.9 23.1 21.4 28.3 20.6 22.5 22.6 24.4 '5 9 '?' 3 18.0 H 3 ii .7 [72 02.0] 71 06.7 03.4 7> 59 9 Wilkes & Loorais . Gilliss, Graham, Nicollet, Loomis . Graham, Lefroy. . Locke, Graham. . . Lee Yard in front of Capi- tol Near Capitol, in gar- den east of it. Public garden, east of Capitol. Near Capitol. Coast Survey Office, Capitol Hill. Georgetown Heights. Between Capitol and city hall. Near White House. Smithsonian grounds & Georgetown IPts. Coast Survey Office, Capitol Hill. Near Capitol, south side. Coast Survey Office. do do do do do do United States Naval Observ't'ry grounds Capitol Hill, corner Second St. east and C St. south, do do Dean Hilgard Gilliss.... Schott ...do Read Schott ....do.. ....do Walker Schott. ....do .. . ....do Harkness Schott. ...do.. ... .do MAGNETIC VARI TABLE Table of Dip compiled by Prof. rn Latitude Longti- Place * N. tudeW. Dip. Date Authority. MASSA'SETTS. ' 1 O Cambridge ... 42 22 71 07 69 51 1780 Mr. Williams. do 42 22 71 07 6 9 41 1782 do do 42 22 71 07 69 4/ 1783 do Springfield ... 42 06 72 36 74 ii 1834 Prof. Bache. RHODE ISL'D. Providence ... 41 49 71 25 74 03 1834 do NEW YORK. - j Albany ff 39 73 73 45 45 74 74 51 1833 Profs. Henry & Cram 40 1834 Prof. Bache do NewYorkCity 40 43 74 01 73 06 1822 Capt. Sabine do " V 74 01 73 27 1825 Sir J. Franklin do j " M 74 OI 72 49 1834 Capt. Back do | " " 74 01 52 1834 Prof. Bache West Point. . . 41 do . ..! 41 23 23 74 74 01 01 73 73 26 1833 Courtenay & Henry 37 1834 Prof. Courtenay PENNSYL'NIA. Philadelphia. . Pittsburgh.... 39 40 57 32 80 12 02 78 oo 1834 Bache & Courtenay 12 1819 Long's Expedition MARYLAND. I Baltimore 39 17 76 38 70 59 1834 Prof. Courtenay VIRGINIA. ! Charlottsville . 38 02 78 31 71 09 1834 Prof. Patterson OHIO. ! | Urbana 40 en 83 42 71 to 1838 p ro f Loche Columbus .... *T 39 o 55 83 3 / * 71 5" pTp , 05 1838 do Springfield. . . Dayton Cincinnati. . . . 39 39 39 53 83 f 4 84 47 09 27 71 71 70 29 1838 do 23 1838 do 46 1838 do KENTUCKY. Shippingport 38 15 85 30 70 15 1819 Long's Expedition MISSOURI. i ' E.Cantonment 41 25 95 44 71 071820 do Cow Island . . 39 25 94 00 69 50 1819 do Charaton 39 10 92 20 69 50 1819 do MAGNETIC VARIATION. TABLE V. Continued. Place. Latitude N. Longti- tudeW. Dip. Date Authority. MISSOURI. FortOsage. . Franklin St. Charles... Belle Fontaine St. Louis Cote sans Des- sein.. 39 10 38 57 38 46 38 43 38 30 38 36 38 36 O ' 9 4 18 92 57 90 48 90 36 90 36 9i 56 90 36 ' 69 iS 69 30 70 05 70 oo 70 30 70 50 70 oo 1819 1819 1819 1819 1819 11819 1819 Long's Expedition, do do do do do do Merrimac Riv. MAGNETIC VARIATION. 59 TABLE VI. Table of Variations compiled by Prof. Elias Loomis in 1838. PLACE. ! t .Latitude. Longitude. Variation. Date. AUTHORITY. 1 MAINE. N. boundary of State. . 48 Timiscuata Lake 47 Matwaska.. 47 *. W. ' ' 0167 55 38,69 o 1268 10 5567 55 2469 35 567 12 30 68 30 4068 55 4068 55 5170 10 4270 53 39> 19 57170 24 0670 35 41 72 10 41 72 10 0570 45 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 5372 20 W. . 17 45 1818 16 31 1818 16 45 1818 14 oo 1817 ii 001838 12 I9I797 14 451825 II 15 1805 13 041837 8 001761 13 oo 1838 7 45 J 763 9 45 1838 7 461771 7 oo 1765 4 15 1810 7 481771 6 261812 6 25 1813 6 17 1814 6 07 1815 6 03 1816 6 02 1817 6 001818 6 03 1819 6 oo 1820 6 07 1821 6 12 1822 6 30 1823 6 40 1824 6 351825 6 351826 Mr. J. Raymond. (. ii < Geo. Report. Chart. Mr. J. Herrick. Prof. Winthrop. Geo, Report. Holland. Pres. Wheelock. < Holland. Nathan Wilde. <. << < it . < ' .. < Source of the St . Croix. 45 Greenville '45 Mouth of the St. Croix. '45 Fork of Penobscot ( 45 HampHen. 44 '* 44 Pownal 43 Umbagog Lake 44 Falmouth 43 Raymond ... 43 Kittery. 43 NEW HAMPSHIRE. Hanover 43 " 4.^ Portsmouth . . . 43 Chesterfield . . 42 42 42 42 A2. 42 42 42 42 4.2 .... . . 42 .... . . 42 42 6o MAGNETIC VARIATION Table VI Continued. PLACE. AUTHORITY. N. W. NEW HAMPSHIRE. Chesterfield 42 42 42 Hinsdale VERMONT. Barton '44 Burlington 44 44 44 44 44 44 44 44 44 Rutland (45 |43 ! 43 St. Johnsbury . Montpelier. . . . Ryegate Rutland . Pownal MASSACHUSETTS. Newburyport J42 Williamstown 42 Deerfield !42 42 Salem . 5372 20 5372 2O 53 J22 20| 5372 20 5372 20 5372 20 5372 20 53:72 20 5372 20 53J72 20| 5372 4672 4472 2873 2873 2873 28!73 28:73 28;73 2873 2873 26j7i I7J72 10,72 3772 3772 37172 4672 4573 34;72 3472 3ii7o 31:70 W. o 6 45 i827 ! Nathan Wilde. 6 52 I2S 7 oo|i829 7 0611830 7 101831 7 i5j'832 7 301833 7 351834 10 46 46 46! 6 59; 5 52 7 15! 5 29! 5 29! 7 54 7 54j 5 05 ; 1 847 A. C. Twining. oo 1 1772' Wright. 51 1837 A. C. Twining. 38 1793 Dr. Williams. 30 1818 Mr. John Johnson. 421822 " i oil 830 " 151831 251832 " *' 501834 4511837 Prof. Benedict. i6|i837jA. C. Twining. 25ji829iExecutive Docu'ts- 00 1 80 1 ! James ' Whitlaw . 03 1 789! Dr. Williams. 041810 01 1811 52 1786 181781 Dr. "Williams. 521786 " " 28181 1 Prof. Hitchcock. 57 1837 Gaz. & Mercury. 021781 Pres. Wiilard Bowditch. MAGNETIC VARIATION. Table VI Continued. PLACE. * l!j 5 ; N I 1 1 AUTHORITY. s MASSACHUSETTS . Salem * 1 1. V ' 31 7O r. C4 A o r V. 20 1808 Dr Bowditch it 42 11 7O C4 6 22 1810 " " Cambridge ,f> O* / w 22 71 O7 7 30 1810 Prof. Farrar u 1 22 71 O7 8 51 1835 " * Boston I'* 21 71 O1 r> oo 1708 Mr. Brattle 8 oo 1742 Prof. Winthrop. 7 2O 17^7 ' ' " . . 1 7 14 1761 Dr. Williams. 7 oo 1763 Prof. Winthrop. \ 46 1782 Dr. "Williams. } 1 6 38 1788 " " Dorchester .... IT la 71 O1 06 1839 M r< Bond. Plymouth 1T C7 70 41 ! 7 oo 1776 Chart Nantucket 1T 17 7O 06 6 70 1776 " RHODE ISLAND. Providence 1T 40 71 ?6 6 30 1769 Dr. West. Newport .... IT 20 71 ?T 6 oo 1776 Chart CONNECTICUT . Pomfret IT C2 71 C7 e 05 1810 Asher Miller. East Hartford IT 46 72 1 -1 46 1810 " " Hartford 1T 46 72 1 e 25 1 786 Dr. Williams. 14 IT 4.6 72 40 c 45 i824N. Goodwin. M IT 46 72 4 I 03 1828 " ' 14 1T ^8 72 1 6 03 1829 ' " Hebron 1T 78 72 T8 ^ 50 1805 Geo. Gillet. rfy 22 72 T8 6 101835! * " Danbury . . . 1 T 22 77 73 e 41 1810 Asher Miller. Lyme New Haven 41 1T 1872 18 72 4 c 30 1810! ' " 47 1761 Pres. Stiles. 41 1 T 1872 1872 58 58 5 5 25 1775 Prof. Strong. 15 1780 Pres Stiles. IT T8/> ! E 10 1 8 1 1 Nathan Redfield. 1 r l8 72 58 35 1819 Prof. Fisher. <1T 1872 5* B 17 i828jN Goodwin. 1T 1872 S C 52 18351 Prof. Loomis. 4.1 1872 ^8 $ i8*6E. C. Herrick. MAGNETIC VARIATION. Table VI. Continued. PLACE. | .| J J Variation. Q AUTHORITY. NORTH CAROLINA. Newbern . . N. o ' : 35 20; 35 2 35 20 32 47 32 47 34 oo 33 07 33 07 30 28 30 27 34 50 34 50 30 40 30 40 3i 34 31 oo 29 58 29 58 32 25 29 41 34 oo 36 10 36 10 3 50 41 oo w. 77 05 77 05 77 05 79 57 79 57 83 20 83 20 83 20 87 12 8 4 3 6 87 47 87 47 88 ii 88 ii 91 25 92 15 90 07 90 07 92 32 94 oo 92 oo g 49 86 49 83 5C 81 31 E. 2 40 2 00 i 45 3 48 2 54 4 3 1 5 30 4 40 6 oo 5 12 til 8 10 7 12 9 oo 9 20 2 00 8 03 9 10 8 41 8 20 6 50 7 07 5 oo I OC I 15 1796 1806 1809 1777 1837 1837 1805 1835 1835 l8 35 1818 1835 1809 1835 1802 1807 1720 1806 1813 1840 1804 1829 i835 1805 1797 1838 Jonathan Price. (i (i Chart. Captain Messrom . Prof. McCay. John Bethune. t Officer of Navy. Mr. P. Mitchel. Jas. 11. Weakly. Mr. Dunbar. Public Surveys. Laval. Lason. Public Survey. Boundary Coms'rs William Dunbar Prof. Hamilton. Public Surveys. Moses Warren. Mr. Mallison. t< SOUTH CAROLINA. Charleston GEORGIA. Athens " .. Milledgeville FLORIDA. Pensecola .... Tallahassee ALABAMA. Florence Mobile MISSISSIPPI. Natchez . LOUISIANA. Cheney ville New Orleans A Point Mouth of Sabine River ARKANSAS. Wachita River TENNESSEE. Nashville KENTUCKY. Augusta OHIO. Portage MAGNETIC VARIATION. Table VI. Continued. PLACE. Latitnde. Longitude . Variation. I AUTHORITY. OHIO. Rapids of Maumee . . . Wooster N. O ' 4i 3 40 49 41 13 40 39 4i 15 41 30 41 oo 41 oo 41 oo 41 oo 41 oo 41 oo 41 oo 41 oo 40 55 39 25 39 25 39 08 39 07 38 48 40 37 39 56 39 45 39 3i 39 28 39 16 39 06 $8 53 Jf 45 58 45 |8 42 ,8 20 [8 oo 8 10 W. ' 83 30 81 58 81 3 83 37 84 23 81 46 80 37 80 50 81 03 81 21 8 8 ! 1 % ll 11 81 48 81 26 81 26 84 45 84 27 82 50 81 28 84 37 83 47 84 16 83 42 81 05 84 27 82 07! 8 5 15 5 23 37 20 3< 40 38 oo 36 30 E. 2 48 2 33 I 14 5 17 430 ) I 20 J050 I 21 i 37 i 48 2 04 2 22 2 19 2 3 3 57 236 2 36 I 2 9 5 10 5 oo 5 oo 2 10 5 23 454 5 30 425 403 458 3 40 5 25! 4351 645! 5 5o! 7 ioj 630] i8ic 1831 1837 1838 1810 1830 1834 1810 1810 1810 1810 1810 1810 1810 1810 1810 1810 1838 1810 1810 1805 1810 1826 1818 1820 1834 Iso6 [810 ^37 t8io 1810 1810 810 Jared Mansfield. C W. Christmas. Prof. Loomis. J. H. Ross. Jared Mansfield. Ahaz Merchant. Jared Mansfield. i < Prof. Loomis. Tared Mansfield. Public Surveys. E. Buckingham. Cudson T agues. Moses Collier. E. Baily. D. Wickercham. Public Survey. ,ames Fletcher. ared Mansfield. ?rof. Dunn. ared Mansfield. i (1 t Hudson Kenton Defiance . . . Cleveland Poland Canfield Berlin Atwater Suffield Coventry Norton Seneca Chippewa Marietta Mouth of Miami River. Cincinnati Portsmouth Sandy New Madison Spring Bank . c t. j opnngboro Wilmington Athens Cincinnati . Gallipolis INDIANA. Madison. South Hanover ; Vincennes .; Falls of the Ohio ; Mouth of the Wabash. ' On the Ohio River. , . 1; 66 MAGNETIC VARIATION. Table VI. Continued. PLACE. Latitude. Longitude . Variation. V AUTHORITY. ILLINOIS. Chicago N. ' 42 oo 39 45 3 52 38 36 37 57 37 04 4i 15 41 10 41 10 41 oo 40 50 40 30 40 20 40 oo 39 30 44 3i 44 3 1 44 31 44 3 1 42 5 42 3 42 24 42 30 38 57 38 36 38 36 37 30 37 oo 37 oo 36 50. 36 40 49 oo W. ' 87 40 90 18 90 12 90 09 89 55 89 oo 88 32 88 32 88 32 88 32 88 32 88 32 88 32 88 32 88 32 85 32 84 5 6 84 28 83 50 84 22 84 22 82 58 82 5 8 92 57 89 36 89 36 90 02 90 O2 90 12 90 02 90 O2 94 oo A 6 12 8 45 8 oo 8 25 7 20 7 20 8 15 8 oo 7 25 6 50 7 43 7 30 7 40 iS 4 30 2 50 2 45 2 00 4 55 4 25 3 13 2 48 II 42 10 47 8 49 7 30 8 oo 8 oo 7 30 8 oo II OI 1823 1833 1835 1810 1809 1809 1821 1821 1838 1838 1833 1823 1823 1822 1821 1838 1838 1838 1838 1826 1826 1822 1810 1819 1819 1835 1827 1823 1823 1823 1825 1323 Long's Expedition Prof. Sturtevant. Mr. Loomis. Jared Mansfield. Public Surveys. Jared Mansfield. Public Surveys. ii ti Geog. Report. Public Surveys. Lucius Lyon. Jared Mansfield. Long's Expedition Col. Nichols. Public Surveys. Long's Expedition [St. Peters. Jacksonville.. Alton Cahokia Kaskaskia Mouth of Ohio River. . A Point ii , ii ii M MICHIGAN. Michigan Shore ... i ( i ( Detroit MISSOURI. Franklin St. Louis A Point M M H MISSOURI & WIS.TERS. Lake of the Woods... MAGNETIC VARIATION. Table VI. Continued. 6 7 PLACE. Latitude. Longitude . Variation. i AUTHORITY. MISSOURI & WIS.TERS. Camp Monroe N. O ' 48 59 48 35 47 5 45 39 44 53 44 4i 43 03 41 25 39-25 W. 92 30 90 oo 96 34 93 08 97 oo 9 5 2 95 44 94 oo E. O ' 13 17 1 I5 6 21 12 29 10 29 12 21 8 49 12 59 ii 32 1823 1823 1823 1823 1823 1823 1823 1819 1819 Long's Expedition [St. Peters. Long's Expedition [Rocky Mts. Island in Rainy Lake . N. Coast of L. Superior Fort Columb. Fir. Co. Mouth of St. Peter's R. Encampment " Fort Crawford Engineer Cantonment. Cow Island 68 MAGNETIC VARIATION. TABLE VII. Table of Magnetic Variations Compiled and reduced to the year 1840, by Prof. Elias Loomis. STATION. 3 ! J * Annual Motion. J* Angle of Maine i O ' O ' , . '48 oo 67 vi W. o 19 12,11838 14 45 1825 10 51 1837 II 20 1838 I 3 4 1837 12 OO 1838 ii oo 1838 12 08 1835 13 oo 1838 12 00 1838 9 50,1835 9 30 1838 9 2111838 7 25(1835 7 3011825 8 4 o| 1838 7 30 1818 8 50 1834 92711840 9 16 1837 8 20 1838 8 2311838 739;i838 847ii8 3 8 9 '5 x 39 7 15! 1838 6 0011820 7 45!i36 8 14 1840 6 04 1827 7 45; 1837 5 45 1818 6 47 1836 6 58 1840 / +8.8 8.1 5-7 I:o 5- 2 5- 2 B 5-7 5-7 5-7 5-7 5-4 5-3 |;| n 5-5 5-5 5-5 5-2 5-5 6-4 5-i 47 S- 2 36 4-6 w. 1 19 30 15 25 II 08 II 30 13 22 12 10 II 10 12 36 13 " 12 II 10 18 9 4i 9 32 7 S 2 851 927 9 32 8 3i 834 7 50 8 58 9 20 7 26 8 14 7 05 8 01 6 58 Penobscot Forks LAC 10 68 26 Barton - 4J /ic ! 72 oq Farmington AA /L2'7O O1 Hampden. * ''I** 4^j/ 2 A A 27iOO 4O Dixfield. AA 30 7O 14 Rumford 4/1 "3Q 7 2 7 Waterville AA 27 6n 32 Belfast 44 18 68 54 West Thomaston. . . Montreal 43 56 69 05 . 4"> 31:7"? 35 Champlain .... 4^ OO T~\ 2O West Chazy 44 5 2 73 2 5 44 40 7C OI Potsdam Keeseville 44 28 71 32 (i Burlington. ,44 28 73 32 . . 44 27 73 Io i " 173 10 I " 73 10 St. Johnsbury 44 26 72 O6 Dial Mountain Near Cedar Point . . . Near West Moriah 44 21 73 49 44 03 74 33 . . . 44 01 73 45 Crown Point. AT. cc 71 27 Hanover . ... 43 42 72 14 Warrensburgh Chesterfield it M Troy 43 2673 45 42 53 72 20 " 72 20 72 20 42 44 73 40 Williamstown Albany . ...42 4373 13 . 42 39 73 45 M 42 7Q 7^ 4"? .... 42 39 73 45 i i MAGNETIC VARIATION. TABLE VII. Continued. 6 9 STATION. Latitude. Longitude. Variation. a 1 n 3| Id S3 1" I Deer-field . 14 o ' ! o ' 234 72 20 W. 5 28 1811 57 w. O ' '4 234 7 2 20 7 57 1837 / 4Q 8 12 Cambridge . . . .4 2 22 71 07 7 30 1810 3 4 " 4 2 22 71 07 9 18 1840 5O 9 18 Southwick 4 2 04 72 46 8 15 1838 w 5O 8 25 House Point 4 Hartford 4 2 03 70 04 I 46 72 41 20 6 03 i835 1820 5-o 5 O 9 45 6 58 Hebron.. . 4 I 70 72 26 6 10 1835 c o 635 Newport 4 I 28 71 21 7 oo 1831 e o 7 4? Ogdensburgh 4 441 75 7i 6 10 1838 j- w 5 A / *rJ 6 21 Rossie . '4 422 75 43 6 43 1830 5 A 6 48 Cazenovia 4 25475 54 4 oo 1837 A A 4 13 Auburn .... '4 25476 38 3 43 1833 42 412 Geneva 4 252 77 03 3 40 1833 A I 4 l8 Hamilton '4 2 48 75 34 4 3O 1837 44 4 43 Homer 4 2 38 76 15 5 05 1840 41 e O5 Ithica 4 2 26 76 36 2 51 1833 4 I 3 2O Oxford . 4 224 75 40 4 3O 1837 44 4 43 Guilford 4 222 75 30 4. 3O 1838 4 I 4 38 West Point 4 12C 74 oo 6 32 1835 4 O 4- O" 6 52 New Haven 4 i 18 72 58 4 35 1810 do East Hampton 4 D5o 72 16 6 13 6 08 1840 1834 4-4 4 4 613 6 34 New York City. 4 347 74 01 440 1824 do J4 do 4< Flatbush .... . . . . >4< D 43 74 oi 3 43 74 oi D 40 73 59 5 40 5 34 4 57 1837 1840 1840 l \ 3.6 5 34 4 57 Philadelphia ... 3 957 75 ii 2 2C 1813 3 6 do 3 West Chester 3 9 57 75 n 957 75 39 3 52 13 25 1837 1832 3-2 3-2 408 3 51 Mackinac 4 c U 84 41 E. 5 2 59 1827 3-9 E 5 2 08 Huron Coast 4 527 83 50 i 55 1840 4.0 i 55 Michigan . 4 431 85 32 4 "?O 1838 3.9 4 22 do 4 do 4 43l|456 4 31 84 28 2 50 2 54 1838 1838 39 39 2 42 2 37 70 MAGNETIC VARIATION. TABLE VII Continued. Station. Latitude. Longitude. Varation. Q i 11 jl O ' 44 31 O ' 81 co E. O ' 2 OO 1838 E. O ' I "J2 Thunder Bay t o* 11 ? fi 83 oo o 4C 1840 U 40 o 45 Pointe aux Barques Michigan 43 5 1 43 5 1 82 42 83 06 . $ 2 06 I8 35 I83C 4.0 A O i 18 1^46 do Pere Marguette River. . . 43 45 43 44 43 36 84 22 8543 83 no 2 55 4 34 12 10 1832 1837 l83C 39 39 40 2 24 4 22 i cq do 43 20 43 OC 84 22 82 26 3 oo o 06 o J 1832 l8lC 39 40 2 29 W. O 14 do Grand River 43 o 42 CC 82 22 86 10 3 E. 2? J, 1O 1831 1877 3-9 30 E. V. 2 4 1 8 Macomb County 42 43 82 10 I 13 1810 9 4 O } 78 do Detroit 42 30 4.2 24. 82 22 82 58 4 25 31 i 1826 1822 3:9 33 do Buffalo 4 2 2 4 42 C2 82 5 8 7q 06 *> -i 58 W. 4-1 2C 1840 1817 4.0 4T -y. 9 4-1 37 Fair View 42 OC 80 2C *o _l_o OO 1818 4 A 4-O Oq Chardon <, 41 36 81 16 1 E. O 1C 1838 I 4 A 'E. o 06 Euclid 4,1 -2-1 81 ic I 1O l82C 4 A O 24 Cleveland 4.1 IO 81 4.6 I 10 n J i82C Brookfield 41 16 80 37 o 35 o 19 o 40 1838 1840 1817 4-5 4-4 42 o 19 o 27 Braceville. . 41 16 81 01 O CO 1878 42 o 42 Hudson 41 15 81 ?6 O C2 1840 4. 2 o 52 St. Clairsville 40 10 8n 5? 3 IO 1820 do Portage 40 10 41 04 80 52 81 34 2 3 I I 1C 1838 1838 2.2 49 2 27 I 06 Wooster 40 48 81 CQ 2 OI 1817 A A I 4 8 Carrolton ^ t" 4O 36 81 10 o 30 1838 4-4 A 7 21 Dover. 4O 72 81 31 I CO 1838 40 I 41 . ' MAGNETIC VARIATION. *' ,/ |> ^ \ C* <& TABLE VII- tantfntfc^V o^ ^ \ *'?*) Stations. i ! I 1 Variation. |.J Ij ; | Coshocton '0 ' 40 18 81 cc -I 30 1838! 4.3 I 22 1838 4.1 2 36 1810 I 2 9 l8 3 8 2. 4 I 33 1838. 4.3 o oo 1835; 3.7 2 48 1838' 4.3 3 H 1838 3.9 3 oo 1838 3.9 5 35 1836 2 7 3 17 1838 3 8 2 30| 1838. 4.3 5 23; 18261 4 5 1 l8 3 8 | 3-2 4 30 18351 3 4 4 54 1818 5.0 3 14 1838! 3-5 3 06 1838] 3.4 5 30 18201 4.8 4 04 i8 3 8| 3.1 4 06 1838; 3.3 3 12 i8 3 8| 43 3 15 1835 j 3.6 3 loj 18381 3.6 5 'SI 1825! 2.0 4 46) 1840! 3.1 2 35! 1838; 3.7 4 35 1837, 2. c 5 9 J 937 2.8 5 09 1837: 2.8 5 oo 1837; 27 .5 04 18371 2.7 5 4 1837, 27 c 27 1818. 2.6 E. ' I 21 I 14 I 24 w. +0^9 2 52 5 24 3 09 2 21 445 3 13 307 2 59 358 3 59 3 03 2 57 3 03 446 2 28 428 5 OI C OI 452 4 5 6 456 c.aa Batesville. in c6 81 17 Marietta 7Q 2C 8 1 26 do do Charlottsville LowerSandusky. . Flat Rock . 39 25 81 26 39 3081 28 38 02,78 30 .. . . 41 2283 10 41 18 84 13 Kalida . 4O C7 84 OQ Logansport . . 4O 4C 86 22 Marion .. 4O "34 8"? OQ Zanesville New Madison .... do Springfield .... 39 59 82 01 39 56:8437 39 5 6 84 37 ,iq C2 8l 4C. Springbank JQ AC Si 47 do Washington. . 39 45 83 47 Springboro 39 31 84 1 6 do Wilmington Athens 39 31 84 16 .... 39 26 83 42 ^Q 21 8^ O4 Chillicothe. . . . 39 21 82 55 Jackson Cincinnati 39 13 82 38 39 06 84 27 39 06 84 27 38 c.4 82 06 38 4485 30 .... 33 S 2 82 39 - - - 33 46 82 37 . . 33 32 82 28 11 27 82 CI do Gahipolis Sou tli Hanover. . . Goshen Lincolnton Applington .v ugusta Waynsboro . 11 O4. 82 OQ Sandersville . . . . 12 CQ 82 CO MAGNETIC VARIATION. TABLE VII Continued. 8 .6 2.6 2.8 2.8 2.8 2.6 1 2.4 2.4^ 2.4 2 4 17! 2.4: 2 l 2.0 9 1 .6 .6 5 5 MAGNETIC VARIATION. TABLE VII Continued. 73 4 Station. 5 3 Longitude. Variation. 1 Annual Motion. Variation 1840. O ' Mobile . . ^o 40 O ' 88 ii 88 16 9400 oo 18 88 32 8832 8832 90 20 90 15 9 15 90 17 90 02 90 02 86 5 2 9053 89 II 8942 89 26 8936 9 45 90 10 8 95 8 9048 9 43 9 33 9 3i 9 2 3 9 *3 9 37 9 5 2 9038 9 57 9 23 90 21 9 37 91 02 O ' 8 10 7 12 8 41 8 13 7 25 6 50 7 43 8 45 j 8 oo 11 45 8 49 7 3 8 oo 6 58 9 05 7 30 8 20 8 48 8 38 9 oo 8 55 8 40 9 oo 9 oo 8 10 8 30 8 22 9 25 9 oo 9 35 9 10 8 45 9 08 9 5 9 J 5 9 20 ? 1840 1840 1838 1838 1833 1833 I8 3 5l 1840 f 1835 1827 1825 1832 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 1840 2.2 1.4 l:i 2-5 2-5 2-5 2.5 2.3 2.3 2.1 2.0 2.O O ' 8 41 8 13 7 20 645 7 26 8 28 747 837 703 73o 642 do 30 42 Louisiana. . . 29 40 Davenport '41 28 Illinois '41 10 do (41 o do 40 50 Jacksonville . . . . kg A* Alton 138 51 do |38 51 St. Louis 38 37 do 36 40 Nashville . '36 I o Prairie du Chien 43 03 Madison 4.7 o"? Point 43 03 Campbells 43 01 Blue Mounds 47 oo Trout Brook. . . . 42 59 Parish's 42 58 Mineral Point 42 5 1 Turkey River 42 42 Log House 42 38 Sherald's Mound 42 35 Little Mahaquita. . . . 42 "U Dubuque 42 29 Galena... 42 28 Sherwood's 42 27 N Branch Mahaquita. . . 42 23 Whitewater 42 1 8 Mahaquita 42 14 Farmers' Creek 42 13 Cheney's 42 12 Mill. .. 42 10 Bridge 42 06 74 MAGNETIC VARIATION. TABLE VII Continued. Station. Latitude. Longitude. Variation. & & Annual Motion. -* |l Small Mill. . . O ' 42 04 42 oo 4i 55 4i 45 4i 39 47 25 47 22 4657 4645 46 41 4640 4632 4632 4631 46 18 4558 91 02 9 5 2 90 40 9 2 3 90 09 88 30 8834 8949 91 22 90 46 86 01 84 38 8635 84 19 83 40 83 50 ' 9 7 I5 8 20 8 22 8 10 5 37 5 24 6 33 8 33 7 43 3 29 i ii 3 39 i 25 12 o 09 1840 1840 1840 1840 1840 l8 4 1840 1840 1840 1840 1840 l8 4 1840 1840 1840 1840 Elkford Iron Ore Wapsipinnicon. . ... Lost Grove Kaweenaw Point. Riviere du Gres Ontonagen River La Pointe Montreal River. Grand Marrais Parisien Island Miner's River Sault St. Marie Montreal Channel Drummond Isle MAGNETIC VARIATION. TABLE VIII. 75 Table of Magnetic Variation and Dip along the At- lantic and Pacific Coasts. Place. Lat. Long. ' Observed and Declination Reduced Dip. 1850. to Year. Dec. Dip. Dec. Dip. MAINE . , ! o o , O , i i ' , Mount Harris. . . 44 4069 08 1 855-7 14 35 76 1414 0676 02 Rag'd Mountain 44 Cam den Village 44 1369 1269 09 05 Isjt-s 14 13 17 57 75 75 42 73 13 5475 3675 32 32 Mount Sebattis . 44 Mount Pleasant . 44 0970 02 70 04 49 1853-6 1851-7 12 14 5475 3276 02 12 14 3575 2475 35 59 Cape Small. ... 43 4769 5 1851-8 12 575 O2 II 5774 58 M. Independence 43 4570 19 1849-8 ii 4675 24 II 4575 24 Burlington, Vt. . '44 2773 '9 1855-7 9 5775 57 9 2975 44 Bowdom Hill . . 43 397 1 6 1851-6 ii 75 14 ii 3275 ii Richm'd Island. 43 337 14 1850-7 12 1875 08 12 1575 07 Fletcher's Neck. 43 2770 20 1850-7 II 1775 18 II 1475 17 Kennebunk Port 43 21 70 28 1851-7 II 2475 14 II 1575 II Mt AgamenticusJ43 1370 41 1847-7 10 1074 55 10 2174 57 Cape Neddick. . 43 12 70 36 1851-7 II 0974 58 II 0074 55 Patuccawa .... 43 0771 ii 1849-6 10 43 76 50 IO 4576 Kittery Point... 43 0570 43 1850-7 10 3 74 57 10 2774 56 Mt. Unkonoonuc 42 5971 35 1848-8 9 0475 09 9 1075 10 Isle of Shoals . . 42 5970 36 1847-6 10 0374 4410 5174 46 Plum Island. . . 142 4870 48 1850-7 IQ 0674 55 10 0274 53 Annis Squam. . . (42 397 40 1849-7 II 37| II 39 Beacon Hill 42 3670 38 1849-7 II 2174 26 II 2374 27 Baker's Island i Light Fort Lee do Coddons Hill. . . 42 3270 47 42 3270 52 do do 42 31 70 51 1849-7 1849-6 1855-7 1849-7 12 10 10 II 1774 IS 5075 50 19 37 12 10 10 II j874 2175 5* 19 26 Little Nahant ... 42 26 70 55 1849-6 9 4i 74 2 9 9 4374 3 Dorchester H'ts. '42 2071 02 1846-7 9 3174 13 9 4874 16 do do do do ! 1855-7 10 H74 29 9 4574 18 Nantasket 42 42 1870 .37- s i 1847-7 1845-8 9 9 3774 1375 16 06 9 9 4974 3575 18 10 Blue Hill 7 6 MAGNETIC VARIATION. TABLE Vin. Continued. Place. Lat. | Long. Observed Declination and Dip. Reduced to 1850. Year. Dec. Dip. Dec. Dip. BeaconPole Hill Manomet Hill., do Copecut Hill. . . Spencer's Hill.. ShootFlyingHill do do Hyannis o Jo ,'\ 41 60 71 27 1844-9 4i 5 6 70 35 x 8 45-7 4i 56 7 35 1846-7 41 43 71 03 1844-8 41 41 71 29 1844-6 41 41 70 20 1845-6 41 41 70 20 1846-7 41 38 70 18 1846-6 41 3770 541845-8 41 28 70 45 1846-6 41 26 70 40 1845-6 41 26 70 40 1846-6 41 23 70 29 1846-6 41 1*7 70 06 1846-6 41 17 70 06 1855-6 41 3071 271844-6 41 22 71 29 1847-7 41 5071 241855-6 41 1971 511847-7 41 20 71 54 1845-6 41 1 8 72 oo 1845-6 41 16 72 20 1845-6 41 06 72 21 1845-6 41 17 72 43 1845-6 41 1772 531847-7 41 1772 531848-7 41 1772 551848-7 41 17 72 55 1855-6 41 1 8 72 54 1848-6 41 16 73 01 1845-7 41 1073 in*45-7 41 09 73 13 1845-7 41 07 73 24 1844-7 41 03 73 32 1844-7 O ' i 9 2774 22 9 '774 30 74 oi 9 974 09 9 0075 7 9 3774 23 9 4073 56 9 22^3 49 8 5474 40 9 12:73 50 8 4473 4i 8 4973 29 8 4973 25 9 J 473 44 9 5974 oi 8 4873 48 9 73 45 9 3174 16 7 33 7 3873 25 7 3o 6 5074 34 7 1472 58 6 151 7 2774 17 7 2574 13 6 32,73 33 7 373 44 6 3873 v 6 ,,,3 6 4973 10 6 3673 02 C ' 9 5374 27 9 3874 34 9 3874 04 9 3574 14 9 3275 13 9 5874 28 9 5774 OD 9 3973 51 9 15 74 44 9 1773 53 9 0673 46 9 0673 32 9 06 73 28 9 3i 73 49 9 3' 73 49 9 I6 73 53 9 JI 73 47 9 0274 05 7 45 8 oo 73 30 7 5i 7 1274 40 7 3773 02 6 37} 7 3974 19 7 3J74 14 6 3873 34 6 3573 33 6 4273 33 7 oo 6 41 73 26 7 15 7 1672 ic 7 0273 08 Fair Haven .... Tarpaulin Cove. Indian Hill.... do Sampson's Hill . Nantucket.. do McSparrain Hill Pt. Judith Light Providence Watch Hill.... Stonington Groton Point. . . Say brook Greenport Sachem's Head . FortWooster. .. do Oyster Point. . . do New Haven. . . . Milford Bridgeport Black Rock Norwalk . Stamford MAGNETIC VARIATION. TABLE VIII. Continued. 77 Place. Lat. Long. Observed Declination and Dip. Reduced to 1850. Year. Dec. Dip. Dec. Dip. Saw Pitts Drowned M'dow Lloyds Harbor. . Oyster Bay ' ' 4i 5973 39 40 5 6 73 3 4Q 5673 25 4o 5273 3i 40 5273 47 40 5273 43 40 5273 43 40 4973 53 42 37 73 44 4i 25 73 57 40 4973 57 40 4374 oo 40 43 74 oo 40 41 74 01 40 41 74 02 40 4773 5 8 40 45 74 07 40 4073 58 40 3274 14 40 28 74 oo 40 28 74 oo '40 2274 43 40 0874 44 40 0774 53 39 5875 I0 39 5875 10 39 5875 23 39 4875 10 39 31 74 17 39 3674 19 39 45 75 34 39 4375 34 39 4175' 30 39 3575 34 1844-7 1845-7 1844-7 1844-7 1844-7 1845-7 1847-8 1847 8 ' ' 5 5872 53 6 04 6 12 72 51 6 5072 59 5 3072 44 7 15 6 10 5 4i 72 53 7 5575 ii 5 3473 55 5 1072 39 6 1372 38 6 25J 6 4072 46 7 0272 59 6 28 72 44 5 3572 52 5 5572 28 5 3772 34 5 5i 72 38 6 ii 72 52 ,5 32 72 42 4 26172 06 4 28 72 22 3 5i 72 ci 4 3272 18 6 4273 01 3 4572 14 4 28 72 12 2 31 71 25 2 4871 57 5 4971 22 j 3 17 7i 35 ' ' 6 2472 59 6 25 6 3872 56 7 1773 04 5 5672 49 7 36 6 21 5 5272 55 7 2674 59 5 0573 43 5 2872 43 6 40 72 43 6 47 6 1172 35 6 34 72 48 6 0072 33 5 5372 56 6 1372 31 5 5572 38 6 1372 43 5 4372 41 5 1972 37 4 44 72 07 4 4572 26 4 0972 05 4 0372 06 6 1872 52 4 0372 18 4 43 72 26 2 4971 29 3 06 72 01 6 0771 26 3 35^ 38 New Rochelle.. . Sand's Point . . . do Leggett. Greenbush . if55-7 if55-7 1846-3 1844-7 1845-7 1855-6 1855-6 1855-6 1846-4 1846-3 1846-3 1844-6 1 55 1 1852-6 1846-4 1846-5 1846-4 if55-7 1854-8 1846-5 1846^9 1846-0 1846-4 1846-4 1846-,; 1846-5 Cold Spring. . . . Bloom'gdale As. Columbia Coll', do Governor's Isl'd Bedloe's Island. Receiving Res'.. Newark . Mount Prospect . Cole Sandy Hook.., do Mount Rose .... White Hill Vanuxem Girard College, do Yard Chew Tuckers Island. Tuckerton Wilmington Sawyer Churcli Landing Fort Delaware . . MAGNETIC VARIATION. TABLE VIII. Continued. Place. Lat. Long. Observed Declination and Dip. Reduced to 1850. Year. Dec. Dip. Dec. Dip. ' I ' O ' O ' ' O ' Hawkins 39 2675 17 39 25 75 20 1846-5 1846-5 2 59 3 14 71 43 71 41 3 16 3 32 71 46 7i 45 Pine Mount. . . . Bom'y H'k Light 39 2275 3 1846-5 3 1 8 7i 39 3 36 7i 43 Port Norris. 39 15 75 01 1846-1; i 04 71 4O ^ 22 71 43 Egg Island Light 39 1075 08 0*s ->: > T 1 1846-5; 3 03 / ^ O 7i 451 3 20 71 49 Town Bank.... 38 5974 57 1846-5; 2 59 71 24! 3 16 71 27 Cape May Light 38 56 74 58 1855-61 3 45 7 1 34 3 17 71 23 do " , 1846-5 3 05 71 26 3 23 71 29 Lewis Landing.. 38 4875 n 1846-5 2 45 3 01 Pilot Town .... 38 47 75 09 Osborne's Ruin. 39 2876 17 1846-5 2 43 1845-5 2 32 71 18 71 48 3 oo 2 55 71 22 71 52 Susque'na Light 139 32 76 05 1847-5 2 14 7i 52 2 26 7i 55 Finlay [39 2476 31 1845-5 2 15 7i 53 2 37 7i 57 do 1846-3 2 18 7i 45 2 37 7i 49 Pools Island . . 39 1776 15 1847-5 2 2 9 7i 52 2 42 7i 55 Rosanne ....... 39 1 7 76 43 1845-4 2 II 72 07 2 34 72 ii Fort McHenry . . 39 1676 34 * ~ 1847-3 2 19 2 32 North Point. ... '39 12 76 26 1846-5 i 37 71 29 1 57 7i 33 do 184.7-3 i 40 1 53 Bodkin Light. . . 39 0876 25 1847-3 2 02 7i 43 2 19 71 46 Kent Island do S. Base Taylor 39 02 76 19 38 5476 22 39 0076 28 1849-5 1845-4 1845-4 2 3 2 24 2 14 71 17 7i 37 71 40 2 33 2 47 2 37 71 17 71 41 71 45 do u 1847-4 2 18 71 19 2 31 71 22 Marriott 38 5276 361846-4 2 09 71 ii 2 27 71 14 do t( I84Q-C 2 05 7 1 13 2 07 7 1 13 Webb's Hill. .. 39 0576 401856-9 Soper's Hill 139 05 76 57 1850-6 Hill's Hill. .38 5476 521850-7 Causten's Hill.. 38 5577 041851-5 2 08 2 7 2 19 I II 71 24 7 ^ **6 71 12 71 19 2 3 2 4 2 15 I 04 71 22 71 50 71 II 71 16 do " " Washington City 138 5377 01 ^55-7 1855-6 I 06 5 44 71 30 71 27 38 5 38 71 19 71 16 5 av , is 38 20 75 06 1853-7 2 33 TO 57 2 14 70 50 Koslyn 37 1477 24 1852-6 o 26 69 17 * J 3 69 12 MAGNETIC VARIATION. TABLE VUL Continued. 79 Place. Lat Long. 1 Observed Declination' Reduced to and Dip. 1850. Year. Dec. | Dip. Dec. Dip. Stevenson's Pt. . Sh^llbank ' ' 36 0676 II 3 6 375 44 35 4775 32 35 4778 38 34 H77 56 34 oo 81 02 33 2279 12 32 5083 38 32 4679 49 32 3380 10 32 0581 05 32 01 80 51 25 40 80 10 24 2781 53 29 0783 03 30 04 84 12 29 4784 36 29 3785 01 29 4085 24 30 04 85 40 30 14 88 oo 30 21 88 32 32 22 86 18 -9 17 89 48 29 02 90 54 29 26 94 53 2 9 13! 94 55 28 55; 95 20 25 57 97 08 32 42117 13 i 1847-1 1847-3 1846-9 1854-0 1854-4 I854-J if53-9 1855-0 1849-3 1850-3 1852-3' 1852-3 1850-2 1849-6 1852-2 1852-3 1853-3 i8m i ' j ' I 4068 54 i 4568 38 i 1368 18 EAST. o 4| 68 12 i 1366 47 3 02 66 08 2 06 65 29 4 3663 51 2 16 64 32 1 2 5464 04 3 4063 40 3 3263 38 4 2556 13 5 2954 26 5 2059 55 "> 2Q ' 1 53 *s s8 5768 40 27 68 21 EAST. 0368 04 3 066 38 3 i8 ; 66 oo 2 22!65 22 4 3! 6 3 4i 2 1464 32 2 5464 04 3 49 6 3 35 3 4163 34 4 . 25 56 13 5 2954 26 5 2259 55 C 71 . . Bodies Island. . . Raleigh, N. C.. De Rosset Columbia, S. C . Allslon Macon, Ga Breach Inlet Edisto Island, E. Base Savannah Tybee Island... Cape Florida. . . Sand Key Depot Key St. Mark's Light Dog Island St. Geo. Island Cape St. Bias.. Hurricane Island Fort Morgan. . . East Pascagonla do Montgomery Ala Fort Livingston . j Isle Derniere Dollar Point East Base Jupiter 5 5i 6 02 t ;?.. j jj ' ' 6 04 1854-1 1854-1* 184.7 4. 6 06 .. 6 08 6 12 | 7 4 6 14' 7 O"? 1847-5 I855-I 1855-3 [853-0 I853-I [848-3 [853-2 [853-4 '853-9 [851-3] 7 1360 27 7-09 5 18 63 05 7 38 8 19 8 5757 53 9 557 42 9 0957 12 9 01 52 24 [2 20 7 1260 30 7 12' ... 5 06 62 52 7 40 8 20 8 5757 53 9 757 42 9 1057 12 9 0252 23 [2 28 Rio Grande .... San Diego T 1 8o MAGNETIC VARIATION. TABLE VIII. Continued. Place. - Lat. Long. Observed Declination and Dip. Reduced to 1850. Year. Dec. Dip. Dec. Dip. San Diego 32 42 33 46 34 27 3* 37 48 40 47 40 45 42 44 46^17 48 22 48 22 H7 13 118 16 120 26 120 43 121 54 122 27 124 II 124 II 124 29 124 02 H 12437 12437 ft? & iSci i O ' 12 32 13 30 13 5 14 17 14 58 15 27 17 06 17 05 18 30 20 9 20 45 21 30 .,., O ' 57 39 59 33 ' 12 32 13 37 13 50 14 13 H 57 15 25 17 03 17 00 18 28 o 57 38 59 32 San Pedro PointConception San LouisOoispo Point Pinos 59 42 59 42 San Francisco. . Bucksport . o^ 1852-1 1853-6 1854-3 1851-9 i8ci c Humboldt Ewing Harbor. Cape Disap'nt. do Scarboro Harbor Waddah Island NeeahBay... 20 19 20 45 21 27 21 41 1852-6 1856-6 71 07 71 07 MAGNETIC VARIATION. 8l TABLE IX. Table compiled from various sources by A. D. Bache, Superintendent U. S. Coast Survey. Station. Latitude. Longitude. Declination 1 Authority. Reiner's Run N. Branch, Susque- hanna, Pa.. O ' 4 I 21 41 3 6 41 49 41 44 41 5 6 45 45 45 36 3834 48 oo 4752 4631 46 04 857 O ' 77 48 82 43 82 51 8307 83 16 8455 8407 91 06 H 103 59 no 36 H3 S 8 118 48 79 29 o W. ! 19 2 I 3 2 18 2 20 2 06 2 I 3 i 53 9 21 905 16 48 19 oo 19 25 19 40 655 1856 1846 1847 1848 1853 1851 1839 1849 1853 < 1849 S. Tyndall. U. S. Top'. Eng's. tt U tt Dr. GoebeL ii f Governor I. I. Stev- ens, North Pacific Railroad Explora- [ tion. Mexican Boundry Sur- vey. Kelly's Island, W. End L. Erie East Sister Isle, W. EndL. Erie West Sister Isle, W. End L. Erie Stony Point ... . Waugosham Point, Mackinaw Strait. East of Duncan City NearNewport,F'k'n. County Mo Near Newport, F'k'n. County, Mo Fort Union . . Fort Benton Fort Owen. Fort Walla-Walla . . Panama, New Gra- nada 82 MAGNETIC VARIATION. TABLE X. Table of Observations in Mexico for "Smithsonian Institute," by Mueller and Sonntag. Station. Lat. Long. Dec. Dip. Date. Vera Cruz ' IQ 12 O ' 06 OQ E. > 8 17 O ' 43 *8 18568 Potrero 18 56 06 48 8 42 ci {4 Orizaba 18 53 Q7 O4 8 28 42 HI || St. Andre's Chalc 18 *Q Q7 14 8 13 42 38 i8c6.a Mirador IQ J7 06 37 8 02 48 1856.10 City of Mexico *y *o IQ 26 7~ J/ 06 OE: y ^ 8 46 /- 41 26 1856.12 MAGNETIC VAEIATI a, I 1 ! u 1 oZgi 0931 oSgi ofrgi uoissaiStp < H t S | S f I JOJJ^ ( ' uoissaa3ip O UB JO uoijBAJasqo jo jaquin^ -f+ :+++-f+H-i-++ -hf co -od ro n f O\vO m to coo xo \ If :*;;!! :5 : : :W, 4 - s o . B - 84 MAGNETIC VARIATION. ge. oggi 0931 uotssaiSip jutiouiv ( sjpaau) notssaiSip uot^Aaasqo UB jo ajq^qcud ;uareddy snoijBAjasqo jo fO O 00 O\ O 60 fO 4-H-+ OOO w O +++++ 1 1 +4-4- i ' 2 JU J?* ^ 2" C ......... Q MAGNETIC VARIATION. UI -BIS 0931 uj CO . fO CO >H .' H4 HH O + : I I 1 uoissaiSip jo upodjj UB jo t-t ON ro COVO *^ ON O\ Ov O O^ "> ^f^O xoO I^IOM roOvO illiij 86 MAGNETIC VARIATION. 0981 uoissaiSip ;unouiy -BIS aipaau) uoissaaSip H jreftioas fijj^sD9 jo qDodg jo suoi^AJasqo jo a 1 1 xnooo 3 MAGNETIC VARIATION. TABLE XII. From U. S. Survey. Reduced by Mr. Schott. 87 LOCALITY. Latitude. Longitude W. of Gr'nwich. & Q Obs'v'd decli- nation. (Variation.) Declination, 1860. Richmond O ' 37 3i 37 14 37 07 3655 37 oo 3651 36 03 36 06 3547 35 46 34 14 33 55 3400 3321 32 46 32 33 32 17 32 01 32 05 30 40 32 5 23 09 2433 2438 25 40 27 36 2 943 3i 54 2 9 S 2 30 25 3i 50 3042 30 23 ' O ' 77 25 77 23 75 57 76 oo 76 18 76 17 7543 76 10 75 3i 78 37 7756 78 oo h 02 79 42 79 l8 80 30 8058 80 oo 81 25 81 71 8337 82 22 81 48 8253 80 10 82 45 84 59 85 05 Illi us 89 oi 1856.9 1852.8 1856 1856 1856 1856 1847 1847 1846 1854 1854 1859 1854 1853 1849 1850 1859 1852 1857 1857 1855 .'& ^ 1843 1860 1860 1843 1858 1857 1857 1855 ' +o 15 -|-o 27 -H 35 + i 28 + i J 5 +i 36 + i 45 -f i 40 + i 13 o 45 i 14 o 38 -3 02 -207 2 16 -254 -3 04 -3 32 -328 4 02 -436 4 46 -615 -425 -5 25 6 12 _| 12 6 24 -6 47 6 02 -652 7 22 +0.38 +0.77 , + i-72 4-1.60 +1-38 -M.73 -(-2.28 -j-2.20 + 1-77 0.50 1. 00 0.62 -3.78 -1.87 1.82 -2.50 -3.03 -3-32 3 40 4-97 4-47 5 19 -4.78 -5.82 -4.17 -498 6.20 5.20 J: 5 7 5.98 6.82 -7-32 Petersburg, Roslyn Cape Charles Cape Henry Old Point Comfort Norfolk Shellbank . Stevenson's Point Bodie's Island Raleigh .... .... Wilmington, De Rosset Smithville Columbia Georgetown Allston Breach Inlet Edisto, East base. Port Royal . . Tybee Savannah, Hutchinson's Island. . . Fernandina. Jf Macon . . Havana, Cuba Key West .... Tortugas Cape Florida Egmont Key. . ... Apalachicola Eufala St. Josephs Bay . Pensacola Pub. Square Lower Peach Tree Mobile Mississippi City 88 MAGNETIC VARIATION. TABLE XII. Continued. LOCALITY. Latitude. * V 1 js "o 1 Obs'v'd decli- 1 nation o '^ I Declinatoin. New Orleans O ' 20 t;7 on , O 7 c? o 7 87 Cubitt 2Q IO 89 i8co 7 7? 7 Passe a Loutre 2Q 1 1 89 OT 1 5 eg 7 7O *9 CQ Cote Blanche . 2O 44 OT 1 1860 -8 ?? -I Gaines Ferry 71 28 07 ^c 1840 8 1 T 8 68 Mouth of Sabine ?-O 41 03 51 1840 -8 -8 67 Ringgolds Barracks 26 23 08 9 1853 MAGNETIC TARIATION 7 . 8 9 TABLE XIII. Compilation of observations on the Western Coast not tabulated elsewhere. Place. Latitude. Longitude, Declination & Authority. San Pedro ... . O ' 33 43 33 46 34 24 34 24 34 27 i&S 3 8i8 4 o 03 40 29 40 40 4306 44 42 47 oo 48 02 48 I 9 O ' 118 15 118 16 119 16 119 41 120 26 120 43 123 02 125 24 124 09 124 29 124 II 124 18 124 07 123 53 122 38 123 41 E. 13 08 1330 10 15 13 28 15 50 14 17 1520 ID OO 15 oo 2 OO 1707 16 oo 18 oo 18 oo 21 30 18 oo 1839 1853 1793 1839 1850 1854 1839 1842 1792 1693 1853 1792 1792 1792 1792 1792 Belcher Trowbridge Van Couver. Belcher. Davidson. Trowbridge. Belcher. Mofras. Van Couver. Carreri. Davidson. Van Couver. < do Santa Barbara. . do Point Conception San Louis Obispo Port Bodega. do Shelter Cove Cape Mendocino Bucksport Cape Blanco. Cape Foul weather Grays Harbor. Port Discovery. Nee-ah-Bay 90 MAGNETIC VARIATION. TABLE XIV. From observations made by Mr. Schott, U. S. C. S., in August and September, 1856, and others. PLACE. 1 Longitude. Declination 1 Oxford 38 41 O ' 76 10 W. O ' 2 41 r8c6 Cape Henlopen Light 38 46 JC OC 2 O4 1856 Dagsborough 38 36 7C ic 2 41 1856 Mason's Landing 38 14 7C JC 2 23 1856 Snead 37 C.8 / J *J 7C 26 2 IQ 1856 Taques . . 37 42 7C n 2 O^ 1856 Scott 37 2O 7C C.4 37 1856 Cape Charles 37 O7 7 1 ; s8 2C 1856 Old Posnt Comfort 37 OO 76 18 JC 1856 Norfolk N. Station 01 *" 36 Ci /- 76 17 3q 1856 Norfolk S. Station 6" 3 l 30 co /~ */ 76 17 27 1856 Cape Henry Light. r s 36 c6 76 oo 28 1856 Ft. Me Henry O" J" 3Q 1 6 *;. 7O 3C 2 2Q 1856 Fredericksburg . . 38 18 77 27 I O2 1856 Richmond . . 37 32 77 26 I S 1856 Humpback Mt 44 C2 68 06 ic 48 1858 Calais 4.C. II 67 17 1C. 21 1857 Mt. Desert AA 21 68 13 1C Id. 1856 South West Harbor I< 2C 8c6 Mt. Saunders 44 3Q 68 36 HCQ 8.56 Bangor Th' Hill 44 48 68 47 15 2O 857 Albany Dud Observatory 42 4O 73 43 8 17 858 Chamcook 4C 07 67 oc 17 36 859 Howard 44 38 67 2* 18 12 859 Western 'Ridge 44 SO 67 27 16 32 8;o Quebec 46 48 71 14. *^ j-" 16 17 859 Portland Bod' Hill 43 3Q * *5 70 16 12 2O 8<;q Portsmouth Kit. Pt 43 OC 7O 4"? II I? 8^0 Plum Island 42 48 70 48 10 c8 859 Ipswich 42 41 70 co II 14. 8co Rockport 42 37 f J J 70 36 ii 37 8cq 42 4O 70 41 II oq 8cq 09 | MAGNETIC VAEIATION. 9 1 TABLE XIV. Continued. j PLACE. 3 Longitude. Declination i ' Beacon Hill 42 36 ' 70 38 O ' 12 O3 Rutland . A/I 36 i8c 72 36 49 i8co Chesterfield : 42 24 72 51 8 cl 1 8 Co Springfield. . . 42 06 72 32 83Q !^59 Washington D. C., C. S., office 38 53 do do do 38 53 do do do 38 53 Srnithville i 33 cc 77 oo 77 oo 77 oo 78 01 2 21 2 27 2 42 78 1856 1860 1863 1860 Port Royal. 32 18 80 38 1860 Mississippi City 30 23 89 01 3 4 7 22 Cubitt. | 29 lo 89 13 / * 732 i8co Passe a Lautre . . 29 1 1 80 oo 73O i8co Belfast 44 26 oy w 69 oo 1C 3O 1863 Roclcland . . 44 06 69 06 1863 Bath 43 55 vy uu 60 40 12 C2 1863 Portland Observatory . .... 43 40 7O 1C 12 l8 1863 " Bramhall Hill. . 43 40 7O 1 6 12 28 1863 Ivy Hill . 41 52 8 26 1863 Tashua .... 41 16 73 1C 8 02 1863 Savannah 32 05 81 05 E. 3 27 7857 Fernandina 30 41 81 28 o / 4 O2 1857 Lower Peach Tree. | 31 50 87 33 7 6 02 i8c7 Pensacola Pub sq 30 25 87 II 6 47 1858 Mobile 30 42 88 02 6 C2 Barrel Key i 29 54 80 07 i8c7 New Orleans 12957 oo 04 751 1858 Point Hudson 48 07 122 45 21 3Q Aulezavik Is ' 59 47 64 13 W. 51 23 1860 Gunstock .... i 43 31 71 22 10 54 1860 Troy Villiaere 42 co 72 II 1861 Wauchusett 42 29 71 C3 8 48 T 86o Provincetown ! 42 03 70 II II 23 1860 92 MAGNETIC VARIATION. TABLE XIV Continued. PLACE. Latitude. Longitude. Declination 1 Wellfleet ' 41 ^6 ' 7O OI W. IO A7 1860 Chatham Light. 41 4O i\j \JL 60 c 7 II 12 1860 Bald Hill. ^.A q\J 41 C.8 "y j/ 72 II 8 CO 1861 Box Hill 41 48 72 27 8 30 1861 Sag Harbor . . .... 41 OO 72 17 8 28 1860 Fire Island W. Base. 4O ^8 71 12 7 46 1860 Brooklyn, Mt. Prospect 4O 4O 71 ^8 / 4 U 6 44. 1860 Barnegat Light . . t i"* ^q 4o Ho6 c 24 1860 Long Branch 3q ^2 Hie ^7 S 18 1860 Absecom Light. ?q 22 74 25 4 ^4. i86n Apalachicola. 2q 41 84 ";Q E J1 6 12 1860 Eufaula . ... ?! KA 85 08 5 I2 1860 Barkley 1O 2"? 87 12 6 42 1861 Cote Blanche. O.f) AA QI 42 821 1860 Ross Mountain T.S IO V *t~ 123 06 16 2^ 1860 3808 122 co 16 iq 1860 MAGNETIC VARIATION. 93 TABLE XV. Observations by A. D. Bache in Pennsylvania in 1840- 41, and Mr. Schott in 1862. PLACE. Latitude. Longitude. | 1 Harrisburgh O ' 40 16 ' 76 13 W. ' 3 12 1840 do Huntingdon 40 16 40 30 7653 78 02 3 44 1 5 2 1862 1840 Pittsburg (Near.) 40 28 80 oo o 08 l840 Brownsville (Near.) 40 oo 70 48 O 2< l84O do do Mercersburg (Near) 40 oo 7Q 47 79 48 77 56 * 3 I 14 O C4 1862 l840 Baltimore 70 l8 // O" 76 77 ** j*f 2 l6 l84O Philadelphia 30 58 7C 10 3"4 do Easton 3958 40 42 75 10 7"> l" 5 oo 3 38 iS^r Williamsport 41 14 77 02 3 71 do Curwinsville 41 14 40 58 77 02 78 36 O O* 4 26 I 4J 184 T Mercer 41 14 80 16 O 07 105 20 45 77 08 ioi 2Q 27 72 76 107 20 14 72 17 108 20 O4 71 154 74 C4 TOO 71 7Q 74 2Q i.\Jy no 71 28 74 oo III 71 2O 77 l6 47 Kanab, Utah, 1872 .... 77 02 112 32 H27 Monte Christo Mill 7Q 17 III fi 17 OC 104 MAGNETIC VARIATION. TABLE XXIV. Observations made upon the N. W. Lake Surveys by General C. B. Comstock U. S. A. PLACE. 1 I I : i -3 1 1, Superior City O ' 46 40 4645 4645 48 15 42 20 42 20 43 55 43 55 43 13 43 13 42 53 42 53 4i 3 4i 30 43 40 43 46 30 46 33 47 28 44 57 44 03 41 51 43 5 43 oi 43 13 43 22 43 44 45 20 45 5i 45 06 45 02 45 44 92 04 92 04 92 04 86 07 83 02 83 02 75 57 75 57 77 5i n 5 i * mi 81 40 Si 40 82 34 8250 8420 87 33 88 02 93 5 87 55 8707 86 13 82 25 82 oo 8231 81 43 81 43 8436 85 35 86 06 85 26 ' 10 3oE. 10 40 " ii 57 o 03 " o 25 " o 18 " 8 o6W. 8 17 3 46 <: 3 36" 3 52" 3 58" 045 " o 51 i 30 " 038" o 04 " 43E. 403" 10 56 " 6 22 3 59" 3 28" i 23 W. o 03 ' i 05 " i 42" 3 59" i 42E. 2 34 " 3 09" 2 43 " 1870.0 1871.6 1873.8 1871.8 1872.5 1873-5 1872.6 1873.5 1873-5 1872.8 1872.6 1873.6 1872.6 1872.6 *&73-7 t t i t 1873.8 4 1 C l860.5 1860.7 l860.8 1860.7 l860.9 It Duluth do Tip Top . . Detroit . .... do Sackett's Harbor. . . do Charlotte do Buffalo do Cleveland. do Forestville Fort Gratiot Fort Brady Marquette Copper Harbor. .... St. Paul Milwaukee Michigan City Grand Haven Fort Gratiot Capa IpperwashC.W Wahley, Michigan . GooderichC.W.. .. Cove Island. . Mackinac North Point S Manitou Island . . . Beaver Island MAGNETIC VARIATION. 1 05 TABLE XXV. Condensed Compilation by Mr. Schott, U. S. C. S. Place. ^fl Observed. 1 Halifax, Nova Scotia I7c6 C 4-12 8^ c 4-12 8? Lat4439'.6N. Long.6 3 35'-3W. / D 1775-5 'Z^ 5 i j 13 58 16.50 j- L m . ** y 14- 5 15 76 1818-0 17-47 17 2 5 1821.7 17.60 I7-52 1852-5 18.17 19.41 18153.0 1800.5 18.85 19.92 19.44 19.76 1866.3 +21.09 +19 97 Quebec, Canada 1640 5 4-i6 o 4-i6 ^4. Lat 46 48. 4 N. 1686^5 j AW . w *5-5 ~ iv J*T 15-44 Long. 71 14'- 5 w - 1810.5 ii .0 11.25 1814.5 11.83 11.67 lf3lS 18345 13 63 14-23 13 54 13-86 184-- 5 14.20 14.66 1858.8 IS 57 15-93 1859-5 1860.8 16.28 +16.47 , '5 97 4-16.04 York Factory I72C C J_IQ O -4-IQ Od. Lat. 57 oo' N. Long. 92 26' W. */ J ' J 1787.5 1819.7 -j-iy .v + l- = 6.0 ~ *y ^"r + 4-93 = 6.06 1843-5 1857.6 = 9-42 = 7-62 = 9-05 = 7-95 Portland, Me 1767 c 4-77^ 4- 8 CK Lat. 43 38.8' N. Long. 70 16 .6 W. * / V J J 1775-5 1845.4 I / / D 8.50 II 47 i j 8.14 "55 1851.6 11.69 11.91 1859-5 12.33 12.33 1863.5 1864.8 12.47 12.73 12.52 12.58 1865.5 12.71 12.01 106 MAGNETIC VARIATION. TABLE XXV. Continued. Place. J j Portland, Me. Continued 1866.1 1873-7 12.72 12.64 +12.80 1 +12.94 '793 5 + 7-63 + 7.63 Burlington Vt . . . 1818.5 1822.5 1826.5 1830.5 7.50 7.60 8.17 7-51 7.69 7 94 8.21 Lat.4428'.2N. Long. 73 I2'.3 W. 1831.5 8.25 8.29 1832.5 8.42 8-37 1834-5 8.83 8.52 1837-5 8-75 8.75 1845.5 9-37 9 33 1855-7 9 95 9 94 1873.8 +11.32 +11.32 Rutland, Vt 1780.-? .1. * oe 4- 6 *i Lat. 43 36'. 5 N. / x O 1810.4 1811.7 i / j i i ~ D * 6.07 1 6.14 6.02 6.l6 1859.6 9.82 9-49 1873.8 +10.67 +10.91 Portsmouth, N. H 1771 1 4- 7 77 4- 7 78 Lat 43 04'- 8 N. Long. 70 43' W. / / J 1775.5 1850.7 i^ t II 7-75 10-50 i^ / /** 7-74 10. 60 1859.5 +11.25 +11. 12 Ne wburyport, Mass 1775-5 1781.5 + 6-75 7-30 + 7-oo 7.02 Lat. 42 48'. 4 N. Long. 73 49 W. 1850.7 10. CO 10.28 18595 +10.97 +10.81 Salem Mass .. 1781.6 + 6 QO + 6 47 Lat. 42 31 '.9 N. Long. 7049'W. 1805.8 1810.8 -j- r^pr 5.95 6.O9 -]- v.^,/ 6.32 6.49 1849-6 10.24 9 75 1855.6 +10.83 +10.40 MAGNETIC VARIATION. Table XXV. Continued. 107 Place. % Observed. } o o Boston, Mass 1700. c -I-IO O + 9-95 Lat. 42 21 '.5. / ^^ J 1708.5 I * v " 9.0 9 45 Long. 71 03'. 8. 1741.5 7-5 1776.0 7.67 6*62 1782.5 6.64 1793-5 6^50 6.82 1807.5 6 08 7.28 1839-5 9 io 9-03 1846.7 9-52 9-49 1855.6 10.23 10.05 1872.7 +"25 -fll.OI 1 708 5 + <> o + r\ ^r\ Lat. 42 22 .9. Long. 71 07'. 7. 1742*5 1757-5 1761.5 y .j 8.0 7-33 7-23 9 3 7.70 7.28 7-17 1763-5 7.00 7 13 1780.5 1782.5 7-03 6-75 6. 90 6 89 1783-5 6-8; 6.90 1788.5 J 6.63 6-93 1810.5 7.50 7.52 1835 5 8.85 9.02 1837-5 9 15 9 15 1840.4 9 30 9 J 6 1842.2 1844-5 9 57 9 65 9 49 9 65 1845.4 9 53 9.72 1850.6 9-5 10.07 1852.5 10.13 10.20 1854.5 IO.2I 10.33 1855 -4 io 91 10.39 1856.5 10.47 10.46 1859.2 10.80 10.63 1867.5 -f-10.70 11.09 Nantflcket, Mass. . , 1775 "> -1- 6. CQ 4- 6. co 108 MAGNETIC VARIATION. TABLE XXV. Continued. Place. 1 s Computed.! Nan tucket, Mass. Continued. Lat. 41 17' Long. 70 06' 1834.5 1838.9 1842.7 o 8.45 9.04 9 15 10 8.64 8 89 9.11 1843 7 9.17 9.17 1846.6 9 23 9 33 1855-6 1867.4 9-97 +10.33 9 3 4-10.42 Providence, R. I 1717. c -I- 9-6o + 9-73 Lat. 4i49'-5- / / J 1720.5 1 -7 9 47 1 ,7 / J 9-49 Long. 71 24'. i. 9 23 , i i 4 I73o'5 + 8.90 + S.8 5 J735-5 + 8.65 + 8.59 1740.5 8.25 f-33 1745-5 7.98 8.02 1750 5 7.07 7.66 1755-5 1760.5 7 33 6-95 7.27 6.88 1765-5 6.72 653 1769 5 6.50 6.29 6-33 6.1$ 1780.3 6.27 6.12 1785.5 6.22 6i7 1790-5 6.17 6.25 1795-5 6.17 632 1800.5 6.25 6-37 1805.5 632 6.40 1810.5 6.40 6-45 1815.5 1819.5 1825.5 6.50 6.62 6.85 6-55 6.75 7.06 1830.5 7.17 7 45 1835-5 1840.5 7 57 8.42 1:3 1841.5 8.52 |. 4 S 1842.5 8 65 1843-5 8-77 8.60 MAGNETIC VARIATION TABLE XXV. Continued. log Place. 1 Observed. Computed. o o Providence, R. L Continued. 1855.6 + 9.52 -f 9-42 Hartford, Conn 1786.5 + 5-42 4- 5.28 Lat. 41 46'. 1810.5 477 5 25 Long. 72 40'.8. 1824.5 1829.0 5-75 6.05 5.60 5-76 1859.6 1867.6 7.29 + 7-82 7-34 + 7-84 New Haven, Conn 1761 c , g 4-6.04 Lat. 41 i8',5, Long. 72 55' .7. */ vl o 1775-5 1780.5 5-42 5-25 5-27 5-07 1811.5 5-i7 4-77 1819.8 4.42 5 .00 1828.5 528 5-35 1835.5 1836.5 568 5 92 5-7i 5-78 1837.9 5.83 5.87 1840.5 6.17 6.02 1845.7 1848.6 6 29 6.58 6.37 O C7 1855.6 1872.5 7-05 | 846 + 8^37 Albany, N. Y 1817.8 + C 71 Lat. 42 39'. 2. Long. 73 45 '.8. 18186 1825.3 5-75 6.00 5-7* 5 78 6.07 1828 6 6.27 6.26 1830.5 6.30 6-37 1831 6 6.54 6.44 1834.8 6.67 6.64 18368 6.78 6.77 1847.9 7.58 7 57 1855.7 4- 7-91 4- 8.16 1856.7 1858.4 + 8.58 + 8.28 -f- 8.23 -f- 8.37 no MAGNETIC VARIATION. TABLE XXV. Continued. Place. j 1 Computed. o o Oxford, N. Y 1794.0 -f-3.OO +2.96 Lat. 42 26' .5. 181? 3 .00 1 S Long. 75 40'. 5- 1828 5 450 3-79 1834.8 1836.8 3 87 4 15 4 '3 4-26 1837 5 45 4-30 1838.5 4 45 4.36 1849.9 5.18 5-14 1857-3 5-73 5.68 1858.1 5-78 5-74 1859.0 1873 9 5.83 6.87 694 1874.4 +6.93 +6.97 Buffalo, N. Y I7Q7 ? o.oo -J-O.OI Lat. 42 52'. 8. / V/ 1837.5 -fi-42 1.17 Long. 78 53'. 5. 1839 5 I 25 1.30 1845.5 1.42 i-7i l8 S9 5 2.94 2.81 1872.5 3.87 389 1873.5 H-3-97 +3-97 Erie Pa 1795.5 0.72 0.72 Lat. 42 07', 8. 1841.6 * / ** +0.50 Long. 80 05 '.4. 1862.6 I873-4 i-55 +2.01 +2.03 Cleveland, Ohio 1796 7 2 OO 2 IO Lat. 41 30'. 3. Long. 8l 42'. / 7 / 1830 5 1831.6 1834-1 1838.1 i 33 1.25 0.83 058 0.98 0.87 0.69 1841.3 0.09 -54 1845-5 1859. c o 65 +077 -0.35 +0.29 1871.8 0.54 0.79 1872.5 17 Lat. 19 12'. Long. 96 09'. 1769.4 1776.5 1815.5 I85&6 1861.0 * * -6.57 10.6 9-3 -ll Z.1/ 6.79 7-46 9.60 965 _i? MAGNETIC VARIATION TABLE XXV '.Continued. Place. 1 O Computed. Mexico, Mexico 1769.8 o c ei Lat. 19 26' Long. 99 06' Acapulco, Mexico. 1804.0 1850.5 1856.9 1858.5 1860.5 1862.5 1867.0 1868.5 1744. c 8 13 8-59 8-77 837 8.50 8-34 8.15 -8.17 7-94 8-75 8.58 8-53 8.46 ' 8.38 8.18 8. ii Lat. i6 J 5o'.5. Long. 99 52'. 3. Panama, New Granada. I79i 3 1822.5 1828.5 1838.0 1866.5 17715.8 7-73 8.67 Q. 12 ,2 9 -8.37 7-8 7.26 S.Ss 8.91 -8.23 7 80 Lat. 8 55' Long 79 30' San Bias, Mexico 1790.8 1802.5 1822.5 1837.5 1840. 8 t 1 1 oo ON 3 d $ TT^ <* | -'"f')^> OMN"W"O" o oo" ^"^vO~ t^'ON co vo q" _ . t*> ON TJ-VO ON 10 rO^O rf r>. to co^P CNOO* CO O \Q _0 I -4+i-H I ++I++++ I. I 1111 + B 10 o o *^ q o o fi ?o^o to O CJ (H fl fl fl ...._. _ , '53 "53 '53 "55 '53 '53 "55 '53 '53 53 '53 '53 '53 '55 '53 '53 '53 '55 '53 '55 I .^ ^fOrfWrOfONN'^'MNWNN -H-HH- iN ONQ *^ ON O ON O ON O\00 O\00 t^.00 VO fO O II II II II II II II II II II 11 II II II II II II II II II _ QQQQQQQQQQQQQQQQQQQQ rO vr> \O rO >o O O u->oO t>- O OO t~ u^oO o rh O vr> rl-vO vO N 10 ro ON N f> t^.vO ^ O vo o O fO' rOM cs HH lo^^ioo O O N ^to^-^voo ~^" cONOtONOOO | - ( '^O'^NNfO voOO O " "vcT^ 6o~ c^>ol^^~ON^o^^rto~b^ to'wi^iooo oo^ ro " ONOO O 00 00 vO -^-OO >-i -< N t^. ONVO OO O\vO N t^ O SM5^tfii*'Af^ rfNS * s MAGNETIC VARIATION. .121 a -a dd O OO to 10 1^ ON * O O\ tN.QO 14-141 I l + l I I I i I I I gggggggggggggggggg *in.un t^oo vo t^ q q vO vAiOM N N N '. ON CO 10*0 ON >O N T}- *-, w-iioio ** *OO 101^ ONVO ^SJo ; ;.H pj'.^ : :"cs ' ' <* . '< ^^f a J 5 i| 3 3||ii >fS .K rf ^-^ 122 MAGNETIC VARIATION. TABLE XXVII. Decennial Table as computed by formulas of Table XXVI., by Mr. Schott. Year (Jan. I). H ci I! rt w 3 11 YorkFactory. 4 & I Rutland, Vt. 1640. o o 4-1"?. Q CO. . 16.4 60 16. c 16.4 80 ^ 1C. 9 9 -4-11.2 1700 10 20 4-i8 6 19 2 40 18.8 4-12 C 17.2 60 Il.O 14.8 4- 8.1 7o 13 7 ii. 6 8 i 80 14. 4. 7.Q 8 2 4-70 9<> 1800 IS* 1C Q 4-0 4- o.i 8-5 8 9 + 7-7 7 ^2 ' > 65 6 2 10 20 30 40 | 60 70 1880 167 17-4 18 i 18.7 19-3 19.8 20.1 4- 20. ^ 4-11.2 12.3 13-4 14.4 16.0 +16.4 =1? 8.1 8.8 7-5 5-3 94 10. 10.6 11.23 ii 82 12.35 12.80 4-11. IT. 7 39 7-58 8.17 8.94 9.62 IO.2I 10.97 4H.Q7 6.14 6-39 8'53 9 53 10.54 4-i i 49 MAGNETIC VARIATION. TABLE XXVII. Continued. Year (Jan. I). .5" Newburyport Mass. j Cambridge, Mass. Nan tucket, Mass. 1640 o o o o o o CO. . 60 70.. 80 90 1700 4-IO o 4- Q 8 10 Q 1 2 20 87 87 1:1 83 40. . 7 6 7 C.O. . 7 2 7 5 60 68 7 2 70. + 7.8 + 7-0 6 7 7 o + 6C 80 90 1800 IO 20 30 40 ::: 70 1880 [i 8.0 8.4 8.8 9 35 9 94 10.55 11.15 11.7 + 12.2 7.0 72 |i 8.4 90 9 .6 10.23 10.83 ii 4 +11. 8 + 6.4 6.2 6.2 6.5 p g.l 10. 9 ii. Q + 12.8 6.6 6.7 7-o 7-4 7-9 8-43 9 05 9.69 10.32 10.90 +11.41 \9 6.9 1:1 8.64 9-33 10.03 10.67 II. 21 +"63 5 6-7 7.0 ft 3.38 8.95 953 10.06 10.54 +10-93 124 MAGNETIC VARIATION. TABLE XXVII. Continued. Year (Jan. i). Providence, R. I. Hartford, Conn. g | U | H 1 6 1 W 1640 . o o o o o CO 60 7O So'..... 90 1700. IO 4-io.4 20 Q 8.0 40 84 CQ 7 7 lo 6-9 + 6.1 70 63 cc 80 6.12 -1- e. 4. C.I 9 6 24 C 2 4.8 + l.oi + o 14 1800 10 20 30 40 ::::: 70.. . 1880 6.37 6-45 6-73 7-43 8.31 9.09 9 65 10.21 + 10.94 5-24 5 46 5.80 6.24 677 7 36 4-7 4.8 5-0 5-43 5-99 6.67 7.41 8.18 + 8.9 ' + 5-4 5-79 6.32 6.97 7.70 8-47 9.2 + 9-9 ' + 1 9 6 3.10 3-40 3-87 4.46 5 *4 6.'65 + 7.38 O.OI + 0.05 0.30 0.74 i 33 2.05 2.85 3-68 + 4 49 MAGNETIC VARIATION. 125 TABLE XXVII. Continued. Year (Tan. i). & 1 Cleveland, O Detroit, Mich. 1. fc Hatborough, Pa. Philadelphia, , Pa. 184.0 o c o o o CO. . 60 . 7O ::::; +8.8 4-85 90 8.8 8.3 1700. . 8.5 7.0 +8.7 IO . . 8.0 7.c 83 20 7.6 7.0 v>. . , 7.2 6-3 7.0 40 - 6.6 5.6 6 2 ">o. . c.q 4-7 c.? 60 C.2 ^.8 4 3 70 4.6 2.Q 7 6 ::::: 4.4 2.2 2.Q 90 . . O.7 -- 2.2 4.2Q 1.8 2 4 1800 10 20 30 40 C:: 70 1880 0.7 0.6 -0.3 +0.03 0.44 0.91 +!! 2.0 1.8 1-5 -1.0 5 0.60 O.I4 +0-3I 0. 7 2 + 1.07 -3.18 3-" 2.90 2-55 -2.09 -156 -o. 99 0.41 +0-13 4.28 4-30 4-47 4.91 5-59 634 6.96 7-43 +7.84 1.8 2.03 2-53 S 4-57 C 9 +6.8 2.1 21 2.28 2.71 3-33 4. ii +6.76 126 MAGNETIC VARIATION. TABLE XXVH Continued. Year (Jan. I). Baltimore. Williamsburcr Va. . wP I s f U Charleston, S. C. Savannah, Ga. i6do v. c o o o o CQ , go 70 80 GO. . 4-4-8 1 7OO 4.8 IO 20 JQ +4 9 40. . } *? +4-2 ^ T to 4.1 60 -4.6 7O 1.2 4 Q & O.7 J.I QO O.2 O.I 5.1 Jsr* I8OO O.2 o.o +0.2 4.Q IO 2O 30 40 ::: 70 +0.6 0.8 1.2 1-7 2.4 2.9 0.4 0.4 0.2 +' 0.6 1.2 +0-3 0.6 I.O 1.49 1.99 2.47 2.90 o.o 0.0 +aI 1.24 i-95 2.71 -4-5 4.04 -3-44 -2.78 2.12 1.52 I'OO 4-9 -4.8 -4-5 4.14 33 2.48 1880 +3.26 +3-5 O.62 1. 80 MAGNETIC VARIATION. 127 TABLE XXXTI. Continued. Year (Jan. i). 1. 1 ? rt rt cJ * j ffi Kingston, Ja- maca. Mobile. New Orleans La. N S d U.y g 1 o CO i .;:.: 70 L 90 ... 1700. . , 10 1 20 .... . 2 3.4 to 1 IL c. 6 2 2.7 2.< 40. . , 4 6.4 4.1 -36 CO 4,7 c.7 lo.::.. -5.8 70. . i ^ Q L 6.5 7-7 90 i 6.3 7.0 -8.5 .1800 . . . 6.2 -6.0 7. T 7 5 Q.I IO 6 26 c.7 7.2 7.0 20 3> 40 ::::: 70. . . 6.9 6.22 6.52 6.12 6.03 5.94 5-47 5-71 4.86 5.44 4.24. 1 ! ASsSK&r, (ORIGINAL MANUFACTURERS.) LYMAN'S SOLAR TRANSIT (PATENT.) For running lines by the sun, independent of *he magnetic needle, and establishing meridians. YOUNG & SONS possess the only graduating engine in this country capable of accurate graduations. The only establishment which includes the facilities for manufac- turing their own optical glasses. CATALOGUES ON APPLICATION. SCIENTIFIC NEWS. WE are publishing, twice a month an ILLUSTRATED JOURNAL, handsomely printed on heavy paper, entitled the Scientific News, devoted to the useful ARTS, POPULAR SCIENCES, INVENTIONS, DISCOVERIES, in MECHANICS, CHEMISTRY and kindred sub- jects. It gives concisely, and in plain English, the latest and best in- telligence in regard to the varied industrial pursuits. It is the aim of the publishers to make it a Scientific News Journal of special in- terest and value to the family and the work shop, as each number will contain a variety of useful hints and practical receipts of value. The subscription is only$i.oo A YEAR. Liberal discounts to clubs and agents. S. H. WALES & SON, ^Publishers, 114 NASSAU ST. NEW YORK. SOLICITOR OF PATENTS. HAVING had more than twenty years experience in SOLICITING AMERICAN and FOREIGN PATENTS, we offer our services to those who desire to protect their inventions in the United States, Canada, Great Britian, Germany, France, Belgium and other countries. Designs Patented, Trade-Marks and Labels Registered, Caveats Filed, Rejected cases prosecuted. Reissue of Defective Patents ob- tained, Interferences managed. Our terms are moderate. No charges for consultation at our office or advice by letter. ADDRESS : S. H. WALES & SON 114 Nassau St., NEW YORK. Holly's Improved Water Works. DIRECT PUMPING PLAN. Combines, with other advantages, over older systems, the follow- ing: 1. Secures by variable pressure a more reliable supply of water for all purposes. 2. Less cost for construction. 3. Less cost for maintainance. 4. Less cost for daily supply by the use of Holly's Im- proved Pumping Machinery. 5. Affords the best fire protection in the world. 6. Largely reduces insurance risks and premiums. 7. Dispenses with fire engines, in whole, or in part. 8. Reduces fire department expenses. Holly's new and improved Compound Pumping Engine is so ar- ranged that it may be operated on the Compound, Low Pressure, or High Pressure principles, and changed from one to the other at pleasure without stopping. This arrangement is essential to securing economical daily pumping, and prompt increase of power for efficient fire protection. In daily working and special tests these engines show a duty equal to 65,000,00x5 to 81,000,000 and over, pounds of water raised one foot, with one hundred pounds of coal, when pumping directly into the mains. Water works on this plan have been put in successful operation by this Company within the last few years in over seventy cities and villages in the United States. For informartion by descriptive pamphlet, or otherwise, address the HOLLY MANUFACTURING CO., LOCKPORT, N. Y. BUFF & BERGER, MANUFACTURERS OF Improved Engineers' ani Surveyors' Instruments, No. 9 PROVINCE COURT, BOStCXEL, Transils, Levels, Chains, LoTelling>&od:, etc,, etc,, etc,, MADE TO ORDER AND ON HAND. BUFF & BERGER'S URGE ILLIlilfiftllD UllLOCIIE m: NJNII1L OF IMPROVED INSTRUMENTS, OF THEIR MANUFACTURE WILL BE SENT ON APPLICA- TION. It contains nine large engravings, prepared from photo- graphs of BUFF & BERGER'S Field Instruments, and gives a description of all their improvements in the in- struments for City, Mining, Railroad, Topographi- cal and Hydraulic Engineering, as well as for Land Surveying. PART II relates to the theory of instruments ; how to use, and how to take care of and adjust them. UNIVERSITY OF CALIFORNIA LIBRARY This Fine y overdue. 12 J947 LD 21-100m-12,'46(A2012sl6)4120 YB 09570 UNIVERSITY OF CALIFORNIA LIBRARY