394 



NA JURE 



[August 26, 1897 



complicated spectrum, such as that which I observed 

 in the corona in 1882. Concerning my observations, I 

 wrote : — ^ 



" Instead of the gradual smooth toning seen, say, m 



Fig. 22. — The Corcna of 1S67. 



the spectrum of the limelight, there were maxima and 



minima, producing an appearance of ribbed structure, 



the lines of hydrogen and 1474 being, of course, over all. 



This observation, however, requires 



confirmation, for the look I had at the 



corona spectrum was instantaneous 



only." 



A change in the spectrum of the 

 corona was placed beyond all doubt 

 in my own mind by my observations 

 in 1 87 1 and 1878. With reference 

 to this I wrote as follows in 1878 

 (Nature, vol. xviii. p. 460) : — 



"The utter disappearance of the 

 large bright red corona of former years 

 in favour of a smaller and white one 

 in this year of minimum struck every- 

 body. Indeed, it is remarkable that, 

 after all our past study of eclipses, this 

 last one should have exhibited pheno- 

 mena the least anticipated. It isolates 

 the matter that gives us the con- 

 tinuous spectrum from the other 

 known constituents. The present 

 eclipse has accomplished, if nothing 

 else, the excellent result of intensifying 

 our knowledge concerning the running 

 down of the solar energy. On the 

 former occasion, in 1871, the 1474 

 ring was very bright, but in 1878 I did 

 not see it at all." 



As the sunspot period is one of 

 about eleven years, it was to be ex- 

 pected that the conditions of 1871 

 would be repeated in 1882 and 1893, 

 and during both these eclipses the 

 1474 ring was photographed with the prismatic cameras. 

 The photographic plates employed in 1875 and 1886 

 were not sensitive to the green, and, since no eye 



1 Roy. Soc. Proc, vol. 34, p. 299. 



NO. 1452, VOL. 56] 



observations were made, we have no evidence as to the 

 visibility of the 1474 ring in those years. 



Although there can be no doubt as to a more or less 

 regular change of intensity in the case of 1474 K, the 

 evidence with regard to other radiations 

 is less conclusive. 



The Form of the Corona in 1896. 



For our knowledge of the Corona as 

 photographed in 1896, we are so far 

 dependent upon the communication 

 made to Nature by Baron Kaulbars, 

 touching the results obtained in Finland 

 (Nature, vol. Iv. p. 298), and the im- 

 portant collection of memoirs communi- 

 cated to the Imperial Academy of 

 Sciences of St. Petersburg, brought 

 together in a volume of 144 pages 

 recently published, giving an account of 

 the work in Novaya Zemlya and on 

 the Amur. The volume contains some 

 admirable reproductions of the photo- 

 graphs taken by MM. Kostinsky and 

 Hansky at Malya Karmakouly in Novaya 

 Zemlya. A copy of M. Kostinsky's 

 second photograph exposed during ten 

 seconds is given here (Fig. 20). 



In a drawing MM. Kostinsky and 

 Hansky have brought together all the 

 details they have been able to trace on 

 their negatives, as well as the positions 

 of all the prominences observed (these 

 are shown in black for greater clear- 

 ness) (Fig. 21). 

 It is certainly very fortunate that these photographs Of 



the corona, together with the still unpublished one ob. 



tained by Sir George Baden Powell, were secured, sinc„ 



they support statements made now many years ago 

 touching the change of form of the corona, as well as 

 its spectrum, in .relation to the sunspot period (see my 

 "Chemistry of the Sun" (1887), pp. 438 et seq.). 



