Again, "Oolite is a limestone containing [should be, consisting of, although the bad drawing given sustains the author] numerous, small rounded [add concretionary] grains, resembling the roe of a fish." He says that, "The coral animal thrives best in pure water, about a hundred feet in depth," in place of the fact that reef-forming corals thrive well at low-tide level and at all depths below down to one hundred feet, while other coral animals occur at depths exceeding a thousand feet. The author attributes the "continually vibrating to and fro" of the continent, which finally culminated in the folding of the rocks producing the Appalachians, to "the tremendous pressure of the two oceans during the Carboniferous age.' Bad hydrostatics, this. A drawing of an Ichthyosaurus represents him spouting like a Right Whale! 3. A Text Book of Elementary Chemistry, Theoretical and Inorganic; by GEORGE F. BARKER, M.D., Professor of Physiological Chemistry in Yale College, New Haven, Conn. vi and 342 pp. 12mo. New Haven, 1870. (C. C. Chatfield & Co.)-Prof. Barker has produced a compact Elementary Text Book, the dimensions of which adapt it to the use of schools, and which is the first in our language wherein "Modern Chemistry" is presented systematically. The style of the work is concise and animated, the illustrations are fresh, the typography is good, and it cannot fail of a hearty welcome among our teachers and learners. 4. The American Naturalist, a popular Illustrated Magazine of Natural History. (Salem, Mass. $4.00 a year).-This monthly Magazine of Naturalist History has won for itself a high place among the Journals of the world. It knows how to popularize science without degrading it. Many of its articles are by some of the best zoologists of the country, and contain the results of original observation. The illustrations are always excellent. A Monograph of N. A. Astacidæ, by Dr. Hermann A. Hagen; No. III, of the Illustrated Catalogue of the Museum of Comparative Zoology of Harvard College. (Published by order of the Legislature of Massachusett-). 112 pp. roy. 8vo, with 11 plates. Cambridge, 1870. To be noticed in our next No. Students' Manual of Comparative Anatomy, and Guide to Dissection, by G. Herbert Morrell, B.A.. B.C.L. Longmans, Green & Co. Aves, ready. Mammalia promised for November. Elementary Treatise on Natural Philosophy, by Sir W. Thomson and Prof. Tait. In the press. Macmillan & Co. The Petroleum Monthly, devoted to the interests of the Oil Business. S. P. Irvin and J. H. Bowman. Editors and Publishers, Oil City, Pa. The first number of this Journal appeared on the first of November. Price three dollars a year. Catalogue of the Principal Minerals of Colorado, with notes by J. Alden Smith. 16 pp. 8vo. Central City, 1870. A Monograph of the Alcedinidæ: or. Kingfishers, by R. B. Sharpe, F.L.S., &c., Librarian to the Zoological Society of London, to be complete in fifteen parts. Price to subscribers, 10s. 6d. each. Annual subscription, £2 2s Only thirty copies now remain of this work. The price will be raised when the work is completed, which will soon be. Intending subscribers are respectfully requested to send their names to the author, at "The Zoological Society of London," 11 Hanover Square, London, W. Also, uniform with the above, A Monograph of the Capitonidæ or. Scansorial Barbets by C. H. T. Marshall, F.Z.S., and G. F. L. Marshall, F.Z.S. To be completed in nine parts. Price 10s. 6d. each. THE AMERICAN JOURNAL OF SCIENCE AND ARTS. [THIRD SERIES.] ART. XII.-Observations on the Variation of the Magnetic Decli nation in connection with the Aurora of October 14, 1870. With remarks on the physical connection between changes in area of disturbed solar surface and magnetic perturbations; by ALFRED M. MAYER, Ph.D. THE aurora of October 14th was first observed by me at 6b 30m P. M. as a ruddy glow in the N.N.E., reaching to about 40° above the horizon. The magnetic observations were commenced at 6b 35m. In the following table the first column contains the times of observation in Bethlehem mean time (long. E. Washington 6m 42s, lat. N. 40° 36′ 24′′), while in the second are given the declinations, + indicating a W. and an E. movement of the N. end of the magnet in reference to the line of mean declination of the day, taken as the mean of the maximum E. elongation at 8h 30m and the maximum W. elongation at 13" 17. This line of mean declination we will call 0°. Time. Declination, - Remarks. 6h 35m+5'70 An arch of silvery light in the N., whose sagitta appears to be in the magnetic meridian. Clouds on the horizon partly obscure its outline. 6 50 +11'46 Arch about 20° in altitude; definition faint. Streamers W.N.W. 7 46 61 1/20 and E.N.E. Aurora the same as at 6 50. 9 5'81 Arch very faint; no streamers. 6'96 to 5'81 [altitude. -2194 to 17'23 Streamers of crimson hue E.N.E. reaching to 60° in AM. JOUR. SCI.-THIRD SERIES, VOL. I, No. 2.—FEB., 1871, Time. Declination. Remarks. 70 48m-12'72 to 6'96 Crimson and greenish streamers N.W. to N.E. 751455 to +8' 7 57 7 52 +10/31 to 11'46 7 55 +21'83 to 25'28 +31'04 to 32/19 8 0+22'98 to 17-22 Greenish streamers extending about 50° above arch. This easterly motion of the magnet is steady and rapid. At the same time deep rosy streamers flash up in the N.N.W. Red streamers have disappeared. Aurora the same as at 8-14. Aurora same as above. 8 10 +2'-24 to These determinations are here expressed graphically. The ordinates above the 0° at 8h (the time of greatest E. elongation) on the morning of Oct. 15. It will be observed, on referring to the column of "Remarks" in connection with the curve, that the motion of the needle coincided in its maxima and minima with the greatest activity of the aurora; and the rapid and steady easterly motion, from 7h 57-5 to 8h 5m-5, of 42'04, is remarkable. Viewed in the declinometer it appeared exactly as though a distant disturbing body was gradually receding from the magnet. The flashing up of brilliant streamers at the time of the beginning of this easterly motion is also to be noticed. The magnet used in these observations is a cylindrical bar 8 ins long 04 in. in diameter, attached to a plane mirror 2 ins. square, and suspended by 2 ft. of untwisted silk fibers. The scale is placed 3 meters from the mirror and with the telescope deflections of 10" can be read. It is to be remarked that the auroral observations do not comport in accuracy with the observations of declination. Having no assistance, I could only observe from a N. window directly after having obtained the scale readings, therefore there are many phenomena of this aurora, which appeared in the zenith, and S. of E. and W., which I did not observe. In connection with the above observation, I will here give an account of a systematic work in which I am engaged and which furnishes a few facts related to the subject of this paper. Every day about 11 (if clear; if cloudy at the nearest possible time thereto) the mean penumbral diameter,* in seconds, of every spot and tache on the sun is measured. These diameters are then reduced to what they would be if viewed normally. Each of these measures is then squared and their sum gives a number which will vary with the umbral and penumbral areas. These daily numbers are therefore directly comparable quantities of the areas of solar disturbance; at least so far as that disturbance is evinced in the formation of spots. Similar measures are made on all the faculæ I can manage. Remarks are also recorded as to changes in spots and faculæ. In connection with the above measures the daily range of magnetic declination is determined to 10". The object of this work is to discover, if possible, a more certainly based physical connection between the daily changes of area of solar disturbance and the variation of daily range of declination. It seems that if the ten-year cycle of solar spots has a physical connection with the varying mean yearly range of declination, that such a connection can be detected and satisfactorily established-if not in the special cases of ordinary daily variation of declination—at least in the cases of great magnetic disturbances or "storms" either accompanied or not by auroral displays. But, as a spot indicates-if not entirely, at When the greater diameter equals or exceeds twice that of the lesser the spot is divided into two or more measures. least principally-an effect of an action which has done its work, we must look more minutely to the changes in area of disturbance. For, if the connection exist, it will show itself principally during the periods of rapid increase or decrease in area of solar disturbance and not when a maximum or minimum area has been reached and remains constant. These remarks are illustrated by measures on the penumbral areas made before and after the auroral displays of the 14th Oct. and of Oct. 24 and 25. The declination range on Oct. 11, three days before the aurora, was 11'23 and increased with the area of solar disturbance to the 14th when it reached 18'43 and the area-number on this day equalled 17075; but on Oct. 15th, the day after the aurora, the declination range had fallen to 11'52 while the areanumber had reached 18875, showing an increase of 1800 from noon of the 14th to noon of the 15th, during which interval the aurora broke forth. On the 16th the range was 11'-52 and the area-number 15795. On Oct. 21, three days before the auroral display of Oct. 24, the declination range was only 3'-94; the area-number 13748. On Oct. 22, decl. =12'75; area-number =14732. On Oct. 23, decl.=11'53; area-number =15991. On Oct. 24, the aurora (as I subsequently learned from the newspapers) was observed at Cincinnati and Cleveland at 5 A. M. I observed myself the great disturbance a few minutes before 8 A. M., when I began my magnetic observations for obtaining the max. E. elongation. At 11 A. M. the measure of solar disturbance gave 16954 and the observed declination range on that day equalled 44'79. On Oct. 25, it reached 54'63.* On Oct. 26, the declination range equalled 14'26 and the area-number had declined to 11959. Here also we observe that the aurora appeared during the period of increase in the penumbral surface. These facts, brought forward as illustrations of my remarks and not as proof of the physical connection of disturbed solar area and magnetic perturbation, for that will require almost constant coincidences, show at once wherein lies the difficulty of such a research; a difficulty which seems not to have been appreciated by those who have given their energies more to a mathematical than to a physical analysis of the connection of these phenomena; and that is, the frequent impossibility of fixing the time at which such a change in area took place. It is very evident, in the first example, that it took place between noon of the 14th and noon of the 15th, but whether it coincided with the auroral display and magnetic perturbation could only have been determined by means of solar measurements, or * On the 24th the disturbance was greatest between 9 and 10 A. M. On Oct. 25. the greatest perturbations were from 12 M. to 2-56 P. M. During the evening displays of this aurora the needle was only slightly deflected. 113 observations were made by me on this aurora. |