NA TURE 



{June i, 1882 



twenty years has in so astonishing a measure verified the 

 prophecy of the " Origin of Species," surely, in conclu- 

 sion, we arc more than ever constrained to agree with the 

 sentiments expressed by its closing words : — " When I 

 view all beings, not as special creations, but as the lineal 

 descendants of some few beings which lived long before 

 the first bed of the Cambrian system was deposited, they 

 seem to me to become ennobled. . . . There is grandeur 

 in this view of life, with its several powers, having been 

 originally breathed by the Creator into a few forms or 

 into one ; and that, whilst this planet has gone cycling on 

 according to the fixed law of gravity, from so simple a 

 beginning endless forms most beautiful and most wonder- 

 ful have been, and are being evolved." 

 ( To be continued. ) 



ECLIPSE NOTES ' 

 III. 

 T^HE eclipse of 1882 is now over, and it is not too 

 J- much to say that the observations have been most 

 successful. Much more work has apparently been done 

 in former eclipses, but it has been of a far more general 

 nature, and. as the old saw has it, dolus latct in generalibus. 

 This year the work has put on very much more of a quan- 

 titative look, and each observation therefore more or less 

 means a real step in advance. And indeed the time had 

 come when this should be so, for day by day the quantity 

 of laboratory work done which can be more or less com- 

 pared with eclipse observations is increasing, and in the 

 case of general observations either in one case or the other 

 comparisons are impossible. I have taken many prior 

 occasions of insisting upon this point ; but perhaps the 

 reason why this principle has been so generally acted 

 upon on the present occasion has been a capital example 

 set to future eclipse parties. Some days before the 

 eclipse there was a regular Congress of the leaders of the 

 different expeditions and the chief observers, held under 

 the presidency of Mahmoud Pacha, the astronomer at 

 Cairo, and not only was the general plan of observations 

 agreed upon but the necessity of a limited field of inquiry 

 was generally acknowledged ; hence at the moment of the 

 eclipse each worker had only a limited part of the spec- 

 trum to study, and the instrument to be employed what- 

 ever its form, and there were many forms employed, was 

 carefully prepared for this part, and this part only, before 

 totality. 



In the way of dispersion, MM. Thollon and Tre'pied 

 need all their confreres, as each had the most 

 powerful form of Thollon spectroscope yet constructed. 

 The dispersion in this instrument is about the same as 

 that given by a Rutherfurd grating (of 17,000 lines to the 

 inch) in the third order, with this important difference, 

 that the quantity of light is much greater, so that a spec- 

 trum can be much better observed. With these spectro- 

 scopes, object-glasses of 9 inches aperture, and siderostats 

 of a simple altazimuth focus were employed. All the 

 other spectroscopic arrangements, whether for eye or 

 photography, were mounted on equatorial stands. The 

 instruments employed for exposing the rapid plates, which 

 recent progress in photographic science has placed in the 

 hands of the astronomers, were perhaps the most compli- 

 cated Thus we had a camera with large lens some 5 feet 

 focus ; on this a slitless spectroscope of the Fraunhofer 



1 Continued from p. 52. 



form, similar to that employed in Siarri in 1875, but with 

 a prism of greater angle in front of the object-glass 

 then a tele-spectroscopic camera of small dispersion with 

 small image of the sun in the slit, and last of all an 

 ordinary camera of small focus. 



Perhaps before I go further it will be convenient to 

 give a collective note agreed upon in a second congress 

 held two hours after the eclipse. This will show the 

 general opinion as to the general results. 



" Unprecedented facilities afforded by Egyptian Govern- 

 ment for observation of the eclipse. The plan carried 

 out was agreed upon by the members of the English, 

 French, and Italian expeditions. The accord among the 

 results is very satisfactory. Photographs of the corona 

 and of its complete spectrum were obtained by Schuster on 

 Abney's plates, H and K being the most intense lines. A 

 study of the red end of the spectrum of the corona and 

 prominences was made by Tacchini. A comet which was 

 very near the sun, and a very striking object, was photo- 

 graphed and observed with the naked eye. Bright lines 

 were observed before and after totality of different heights 

 by Lockyer, and with intensities differing from the Fraun- 

 hofer lines by Lockyer and Tre'pied. An absolute deter- 

 mination of the place of the coronal line at 1474, of 

 Kirchhoff's scale, was made by Thollon and Tre'pied. The 

 absence of dark lines in the corona spectrum was noted 

 by Tacchini and Thollon with very different dispersions. 

 Many bright lines in the violet were observed in the spec- 

 trum of corona by Thollon, and were photographed by 

 Schuster. Hydrogen and coronal lines studied in grating 

 spectroscope by Puiseux, and in direct-vision prism by 

 Thollon. Rings observed with grating by Lockyer, first, 

 second and third orders. Continuous spectrum relatively 

 fainter than in 1878, and stronger than in 1871. Intensi- 

 fication of absorption observed in group A at the edge of 

 the moon by Tre ; pied and Thollon. 



" Lockyer, Tacchini, Thollon." 



Having given the collective note, I maybe permitted to 

 refer first to those observations which specially bear upon 

 the matter dwelt upon in these notes — observations 

 touching the bright lines seen before and at the moment 

 of totality. 



The importance of this part of the work arises from 

 the following considerations : — If there be a layer of a 

 certain height, by the absorption of which the lines of 

 Fraunhofer are reversed, the lines visible under the stated 

 conditions during eclipses will all be of the same height, 

 and their intensities will all be those of the Fraunhofer 

 lines ; if, on the contrary, the reversing layer is a myth, 

 as I believe it to be from a consideration of all the pro- 

 minence and spot work done up to the present time, the 

 lines will not be all of the same height, and the intensi- 

 ties will widely differ from those of the general spectrum 

 of the sun, for the following reasons : — 



As explained in my first batch of notes, it is most 

 probable that the solar spectrum is built up of the ab- 

 sorption of different layers, and not of one, thus — 



A, B, C, layers. 



A, layer nearest the sun, and therefore hottest, and 



