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IV. MISCELLANEOUS SCIENTIFIC INTELLIGENCE. 1. New Tables of the Planets.-Prof. Newcomb in his report as Superintendent of the Nautical Almanac announces the substantial completion of the work of determining the fundamental constants of astronomy and the elements and masses of the major planets from Mercury to Saturn inclusive. He hopes to have the tables from Mercury to Mars inclusive completed by the end of the fiscal year. The tables of Jupiter and Saturn were completed by Dr. Hill during the last fiscal year. This leaves only Uranus and Neptune to be worked up.
Prof. Newcomb takes this occasion to present a general report upon the nature and objects of this work. The best of existing tables, those of Leverrier are by the lapse of time and by the lack of homogeneity in the elements employed, quite unsuited to the present needs of astronomers. There was needed a partial or complete reduction of all good observations of the sun and planets made since 1750. The actual number of separate meridian observations of the sun and the three planets Mercury, Venus, and Mars used by Prof. Newcomb was 62,030, against 10,893, used by Leverrier. The work of computation required to utilize all these observations and determine simultaneously the 23 unknown quantities involved can be appreciated only by those who have experience in such work. This immense labor has been secured by means of extra appropriations of $3,000 to $4,000 annually, together with such economy in the regular work of the Almanac office as was practicable.
Prof. Newcomb speaks of the increased demand for accurate positions of a much larger number of fixed stars than have heretofore been given in the Ephemeris. This increase is greatly needed, and in making it, we hope that the additional stars will be selected after consultation with the superintendents of the British, German and French Almanacs. A common list of stars may or may not be desirable. If a common list is not desirable, the differences in the lists should be for explicit reasons.
2. Ostwald's Klassiker der exakten Wissenschaften. Leipzig (Wm. Engelmann).—This series of classical scientific memoirs continues to grow in value as it grows in size. The papers, selected for republication, are well chosen and the originals being for the most part difficult of access, the library becomes of the first importance to the student in the subjects which it embraces. The latest additions are as follows:
No. 54. Anmerkungen und Zusätze zur Entwerfung der Land und Himmelscharten von J. H. Lambert (1772) 93 pp.
55. Teber Kartenprojection: Abhandlungen von Lagrange (1779) und Gauss (1822) 101 pp.
56. Die Gesetze der Ueberkaltung und Gefrierpunktserniedrigung. Zwei Abhandlungen von Sir Charles Blagden (1788). 49 pp.
57. Abhandlungen über Thermometrie von Fahrenheit, Réauinur, Celsius (1724, 1730-33, 1742). 140 pp.
58. Chemische Abhandlung von der Luft und dem Feuer von Carl Wilhelm Scheele (1777) 112 pp.
59. Otto von Guericke's neue “Magdeburgische ” Versuche über den leeren Raum (1672) 116 pp.
OBITUARY. Lewis R. Gibbes.—Dr. Lewis R. Gibbes, a scientist of very varied learning, died on the 21st of last November at Charleston, S. C., in the 85th year of his age. He was born in Charleston on the 14th of August, 1810. He entered on a course of medical study in 1830; but before the close of 1831 he was appointed Tutor in Mathematics in the College of South Carolina, at Charleston. At the revolution in the College, of December, 1834, when, owing to opposition to the President, Dr. Cooper, all the officers were requested to resign, he was set adrist with the rest. But in the new organization which followed the next day, Mr. Gibbes was made Professor of Mathematics. He resigned his position the following year, and in 1836 visited Paris for the purpose of completing his medical education, and gratifying his desire for knowledge in other directions. In 1838 he was again a Professor in the Charleston College, teaching mathematics, physics, chemistry and mineralogy. Botany and some departments of Zoology were also among his special studies. He published various papers on the Crustacea of the American coast, and showed his comprehensive knowledge of the subject by his revision, in 1850, of the species in the various United States collections, to which he added valuable notes and descriptions of new species. His encyclopedic tastes and knowledge are further shown by his astronomical work, especially between 1845 and 1854, when he published, besides other related papers, one on a comparison and discussion of all the observations made in the United States on the transit of mercury of May, 1845, and in 1849-50, while engaged in observing occultations of fixed stars by the moon, devised and constructed an occultator for the purpose “ of obtaining the approximate times of disappearance and reappearance with less labor than by calculation.".
As President Shepherd in his tribute to Dr. Gibbes, says: Astronomy was his passion, but he cultivated nearly every phase of our complex modern science, and cultivated none that he did not dignify and adorn. As a teacher he was lucidity itself. He not only taught so that he might be understood by the pupil, but so that he could not be misunderstood. He ever manifested a spirit of absolute consecration to his ideal as a scientist, an insatiable quest of knowledge, undiminished even in the view of death, and respect and reverence for the eternal verities of the Christian faith.
The death of FATHER DENZA, Director of the Vatican Observatory, is announced by telegraph.
AMERICAN JOURNAL OF SCIENCE
Art. VI.- On the Relation of Gravity to Continental Eleva
tion ; by T. C. MENDENHALL.
[Read at the November meeting of the N. A. S.] NEARLY all of the earlier determinations of the force of gravity in the United States were made in the vicinity of the Atlantic Ocean, not more than one or two stations in the Mississippi Valley having been occupied previous to the year 1890. A determination had, however, been made on the Pacific Coast, at San Francisco, and pendulums had been swung for the same purpose on the summit of Mount Hamilton, at the Lick Observatory.
The development in the Coast and Geodetic Survey of the system of gravitation measure by means of half-second pendulums, to which reference has already been made in previous papers, made it possible, at a vastly less expenditure of time and labor, to execute an extensive series of gravity determinations as near as' might be along the 39th parallel, extending from ocean to ocean, thus following nearly the line of the great trans-continental arc.
In the year 1893, an officer of the French Geographic corps, Colonel George Defforges, widely known for his investigations in connection with gravitation, visited this country, bringing with him pendulums which he had swung at several European stations, for the purpose of occupying the fundamental stations of the Coast and Geodetic Survey, and observing at a few isolated points which might be available during the period of his stay. Colonel Defforges swung his pendulums at several stations previously occupied by Coast Survey observers, and at
one or two stations in the interior at which the Coast Survey had not before observed. These fundamental stations, in connection with those already occupied by the American observers, made it possible to form a general idea of the variations of gravity along the trans-continental line and to compare such variations with elevations above the sea.
At a meeting of the National Academy in April, 1894, the writer presented a brief résumé of these results, including a diagram showing the departures of actual gravity from what might be called normal values.
During the summer of 1994 a very extended series of gravitation observations were made, by the new pendulum apparatus of the Coast and Geodetic Survey, by a party in charge of Assistant George R. Putnam. An examination of the details of the results of this series of observations proves that they were very carefully executed, and must be regarded as having a high value from the standpoint of accuracy. The results are of very great interest, and the special point to which attention is now called is the relation of this series of relative values of the force of gravity along this great continental arc to the various elevations above the sea of the stations at which the work was done. Below is a list of the stations occupied, arranged in the order of their longitude, beginning with Washington, near the Atlantic Coast, and ending with San Francisco, Cala. Abstract of preliminary results of relative gravity observations with half-second
Lat. Long. feet. observed. Level. Helmert. 6.-9. Washington.....
38° 53' 77° 00' 46 980 098 980:101 980 047 +054 Deer Park .. 3925 79 20 2515 979.921 980.068 980 094 - 026 Cleveland ..
41 30 81 40 689 980.227 980.268 980-280 -012 Chicago ....
41 47 87 36 597 980.265 980-300 980-306 -006 St. Louis .. 38 38 90 12 504 979 987 980 017 980:024 --007 Kansas City 39 06 94 33 913 979 977 980.031 980.066 --035 Ellsworth .. 33 44 98 14 1470 979.912 979.999 980.033 --034 Wallace ......
38 55 101 35 3281 979.742 979 934 980:049 -115 Colorado Spgs.. 38 50 104 49 6063 979:475 979.831 980 042 - 211 Denver........ 39 41 104 57 5375 979-595 979.910 980.117 - 207 Pike's Peak.... 38 50 105 02 14140 978.940 979.769 980.042 -273 Gunnison' ....... 38 32 106 55 7679 979:328 979:778 980.015 - 237
39 04 108 30 4570 979.620 979.887 980.063 -176 Green River .... 39 00 110 05 4079 979 622 979.861 980.057 -.196 Grand Canyon .. 44 43 110 29 7828 979 885 980:344 980 571 -227 Norris ......... 41 44 110 43 7466 979.925 980-362 980-572 -210 Lower Geyser Bas., 44 33 110 48 7219 979.918 980.341 980 556 -215 Pleasant Valley . 39 51 111 027187 979:499 979.920 980-132 - 212 Salt Lake........ 40 46 111 54 4340 979.790 980.044 980.214 -170 San Francisco .... 37 47 122 26 375 979.951 979.973 979.946 + 0265
It will be seen that there was no great variation in latitude among these stations, and that in longitude they are quite well
distributed, except that there remains for the time being a break of a little more than ten degrees between Salt Lake and San Francisco. It is to be hoped that the Coast Survey will in the near future be able to fill up this break. The elevations above sea level are also given, together with the force of grav. ity at each station. These values of the force of gravity must be accepted only tentatively, as it will appear that they are all made to depend upon the value at Washington. This value was adopted after an examination of several values for this point, some of which were not very satisfactory absolute measurements, and others the result of relative determinations at Washington and various absolute stations in Europe. It is not believed that the error of the assumed value is very great, and hence the table of values given may be considered as very close approximations to the absolute results. Relatively the degree of accuracy is, of course, very much higher.
Now the question of the existence at any point of an excess or deticiency of the force of gravitation is one which depends, of course, purely upon definition. Strictly speaking there can be no excess or deficiency of gravity at any point on the surface of the earth, for it must be whatever it is; but if comparisons be made of actual values with a theoretical distribution of the force of gravity some interesting conclusions can be drawn from an examination of the excesses and deficiencies. Accepting any spheroid, as Clark's spheroid of 1866, and assuming any distribution of gravity that may be chosen, the theoretical values may be calculated for any point on the surface of the earth, and the difference between these theoretical values and those actually observed would naturally lead to some conclusion as to the correctness of the theory of distribution which had been adopted. However, the greater part of the deviation of the observed values of the force of gravity at the several points given in the table above, from the values as distributed over Clark's spheroid, in accordance with the generally accepted formula, is due to the elevation of these points above the sea level. Now in order to bring such observations at elevated points into the same category as those observed at or near the surface of the imaginary spheroid, it is necessary to reduce them to the sea level, and in doing that we are obliged to take account not only of the actual diminution of the force of gravity due to the greater distance of the point from the center of the earth, but also the attraction of the continental mass which lies above the spheroidal surface. This correction is usually made by the application of a formula due to Bouger and used by him inany years ago for making reductions of observations made by the Peruvian expedition of the French Academy. This formula is :