July i, 1887.] 



SCIENCE. 



Prussia — by the way, why is not the perfectly familiar Cultur- 

 kampf used in the title, instead of a word which is partly foreign 

 in form, and wholly so in sound ? — is the first clear and adequate 

 description in English of that very significant and important move- 

 ment in Prussia's political history. The book-reviews are as numer- 

 ous and as well done as usual. We observe that a very severe criti- 

 cism is passed on the volume on New York in the 'American Com- 

 monwealth ' series. Prof. Richmond Smith reviews Prof. H. C. 

 Adams's ' Public Debts ' in a very appreciative manner, describing 

 the book as "careful, scholarly, and extremely suggestive." We 

 observe this sentence, which Professor Smith uses in speaking of 

 the industrial effects of public debts : " Professor Adams's discus- 

 sion is acute and logical, and, in my opinion, a distinct advance 

 upon the treatment of the same question by Leroy-Beaulieu, the 

 distinguished French financier." 



— Some remarkable facts as to the change in the population of 

 Alsace-Lorraine are brought out by the recent publication of the 

 results of the census taken in those provinces in December, 1885. 

 The statistics are published in the Landes Zeitu7ig, the official 

 journal in the provinces. It appears that in December, 1885, the 

 total population was only 1,564,355 as compared with 1,566,670 

 five years before, — a decrease of 2,315 in five years. Classified 

 according to nationality, there were in December, 1885, 1,368,711 

 natives of Alsace-Lorraine, 151,755 Germans from other parts of 

 the empire, and 43,829 foreigners ; whereas in December, 1880, the 

 natives of Alsace-Lorraine numbered 1,418,025, and the immigrants 

 from Germany only 1 14,797. So in five years the native popula- 

 tion has decreased by 49,254, while the immigrants have increased 

 by 36,958. The increasing emigration of the native population ex- 

 plains their falling-off ; and the Landes Zeitung estimates, that, if 

 the present rate of diminution continues, the native population will 

 have disappeared entirely in less than thirty years. 



LETTERS TO THE EDITOR. 



%" The attention of scientific men is called to the advantages of the CO 

 columns of ScizuCE. for placing projnptly on record brief preliminary notices of 

 their investigations. Twenty copies of the number containing his communication 

 'will be fur7iished free to any correspondent on request. 



The editor will be glad to publish any queries consonant with the character of 



Correspondents are regttested to be as brief as possible. The writer s name is 

 in all cases required as proof of good faith . 



The Total Solar Eclipse of 1886. 



The following brief account is penned in order that it may be 

 published in time to be of service to the observers of the eclipse of 

 1887. 



It was found that by using rapid gelatine plates an exposure of 

 one or two seconds was sufficient to show the details of the inner 

 corona satisfactorily with an ordinary telescope-lens. With a 

 portrait-lens the ratio of whose aperture to its focus was as one t& 

 five, one or two seconds' exposure showed the outer corona satis- 

 factorily, as far as a distinct falling-off place in the light. This 

 was at a distance of from 1 5' to 30' from the limb of the moon. 

 Beyond that the light was very decidedly fainter, and was shown 

 best by exposures with lenses of the same ratio, of from eight to 

 forty seconds. This light extended to from one to two degrees 

 from the moon's limb, was very faint, and seemed analogous in 

 character to the zodiacal light. It was clearly not a mere reflec- 

 tion of the corona in the camera-lenses, as it did not extend over 

 the moon's image, where it would, in that case, have been brightest. 

 Measurements of the actinic brightness of different portions of the 

 corona were made, which will appear in a subsequent paper. 



The corona showed the usual short rays of light proceeding from 

 the sun's poles, and from the south-western quadrant a very con- 

 spicuous ray, appearing like a hollow cone projected to a distance 

 of some twenty minutes of arc. On one of the long-exposure plates 

 it was noticed that this was crowned by a curious fountain-like 

 structure, — three fine jets, about a minute in diameter, shooting 

 up 35' to 40' from the moon's limb, cur\dng round, and falling 

 back towards the sun. On closer inspection, seven other jets were 

 counted, all more or less well marked, and all proceeding from the 

 summits of bright rays of the corona. Some of these returned to- 

 wards the sun, but the majority faded away at about 30' distance 

 from the limb. Unfortunately, only one of the plates was taken on 



a sufficiently large scale, and with sufficient exposure, to show this 

 phenomenon, and the whole appearance may therefore be due to 

 defects in the gelatine film of that plate. But, as the markings are 

 certainly on the plate, I have ventured to describe them ; the more 

 readily, as a somewhat analogous appearance, though on a 

 smaller scale, is represented in Mr. Ranyard's ' Obsen-ations made 

 during Total Solar Eclipses ' (Memoirs of the Royal Astronomical 

 Society, xli., Plate x.) 



Passing from the corona to the prominences, a number of them 

 were seen near the equator, on both sides of the moon ; but the 

 most conspicuous one of all was situated in the north-western quad- 

 rant. It extended to a height of about one hundred thousand 

 miles, and had apparently a somewhat spiral stnacture. The spec- 

 tra of the various prominences were shown very clearly by the pris- 

 matic camera. In the equatorial ones the hydrogen and H and K lines 

 were prominent, superposed on a background of continuous spec- 

 trum ; but in the large prominence the hydrogen lines were all ab- 

 sent, confirming Professor Tacchini's observation of its invisibility 

 both before and after totality. 



The H and K lines, however, were strongly marked ; and it seems 

 quite probable that numbers of prominences may escape ordinary 

 observation by the spectroscopic method, merely because they shine 

 only by the actinic radiations, and are hence invisible to the eye. 

 The remedy for this difficulty would be, either to use a fluorescent 

 eyepiece, or, better, to photograph them, instead of trusting merely 

 to eye-observations. The position of the maximum density in the 

 continuous spectrum of the prominences was found to be quite dif- 

 ferent from that of the corona. In the prominences and in the sun 

 it is found to be not far from the G line, while in the corona it lies 

 between G and F. This may indicate, that, besides the gaseous 

 constituent, the corona is composed also of incandescent solid or 

 liquid matter, which, while cooler than the sun, still shines by its 

 own light. In this case, the position of the maximum might give 

 us a hint as to the temperature of the corona. 



Photometric measurements of the general light during totality 

 were made, which, roughly stated, indicate a brightness equal to one 

 candle at about 29 inches or 73.5 centimetres distance. Previous ob- 

 servations by Mr. W. O. Ross in 1870 had given 18.5 inches; and 

 by Dr. J. C. Smith in 1878, 51.25 inches. It had been intended to 

 make some observations on the actinic power of the sky during the 

 eclipse, but unfortunately the plates reserved for this purpose were 

 found to have been spoiled by the excessive moisture of the Grenada 

 climate ; so that no result was obtained. In some of the longer 

 exposures, however, where a large field was used, portions of the 

 landscape appeared upon the plates, showing that considerable 

 actinic radiation was given out even during the total phase. 



A large number of persons observed the shadow-bands, which 

 appeared before and after totality. The general result of their 

 observations indicated that the bands were about five inches wide 

 and eight inches apart, that they were colored like the spectrum, 

 and that they moved with a velocity comparable with that of an 

 express-train ; at all events, much faster than a man could run. 

 Before totality the bands lay N. 12° W. and S. 12° E., and travelled 

 west : after totality they lay N. 60'=' E. and S. 60° W., and travelled 

 north-west. The wind during totality blew from the point S. 35° 

 E. : during the partial phases it was blowing from six to nine miles 

 an hour, but fell during the three minutes of totality to between two 

 and four miles. The thermometer ceased rising as totality ap- 

 proached, but afterwards rose more rapidly. The extent of the 

 effect produced on it amounted to .4° C. This figure may seem 

 small, but it must be remembered that the fluctuation between 

 sunrise and noon in these tropical islands in the summer season sel- 

 dom exceeds two or three degrees. 



In general results, the expedition may be said to have proved 

 successful, although one of the most important instruments, the 

 forty-foot photo-heliograph, failed to work, through lack of sun- 

 light previous to totality, which prevented the application of the 

 necessary adjustments to the mirror. It is hoped, however, that this 

 omission will be in part rectified at the present ecHpse, as a similar 

 instrument, even better equipped, has been sent in charge of Pro- 

 fessor Todd to Japan ; and, if the weather favors, some excellent 

 pictures should be the result. W. H. Pickering. 



Harvard Observatory, Cambridge, June 23 . 



