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MR. J. N. LOCKTBR AND DR. SCHUSTER ON 
less well defined than on the present occasion. The characteristic feature of the eclipse 
in 1868 was formed by the protuberances, and the corona fell more into the back- 
ground. This time the protuberances could only be seen with the naked eye by a 
few, and the corona surrounded the moon like a regular and well-defined star. 
Some observers note the particular appearance of one protuberance, which they say 
was of a white dazzling light, and stood out bright from the background, while the 
other protuberance appeared red and dark on a bright ground. On referring to our 
photographs we find that the white protuberance was indeed by far the strongest, and 
contained a great quantity of the particular ultra-violet light, of which we shall have 
to speak in discussing the results of the prismatic camera. 
VI. RESULTS OF THE PRISMATIC CAMERA. 
The plates exposed in the prismatic camera present at first sight a somewhat 
complicated appearance. Two plates have been exposed during totality. No. 1 
(fig. 9, Plate 10) during one minute, and No. 2 (fig. 8, Plate 10) during two minutes. 
They show only such differences as are to be attributed to a difference in phase of the 
eclipse. 
As the protuberances must form the scale to which we shall have to refer the rest, 
they are the first object of our investigation. 
1. Protuberances. 
During the first part of the eclipse two strong protuberances close together are 
noticed* ; on the limb towards the end these are partially covered, while a series of 
protuberances came out at the other edge. The strongest of these protuberances are 
repeated three times, an effect of course of the prism, and we shall have to decide 
if possible the wave lengths corresponding to the images. We expect d priori to find 
the hydrogen lines represented. We know three photographic hydrogen lin es : F, a 
line near G, and h. F is just at the limit of the photographic part of the spectrum, 
and we find indeed images of protuberances towards the less refrangible part at the 
limit of photographic effect. For, as we shall show, a continuous spectrum in the 
lower parts of the corona has been recorded, and the extent of this continuous 
spectrum gives us an idea of the paxt of the spectrum in which each protuberance 
line is placed. We are justified in assuming, therefore, as a preliminary hypothesis, 
that the least refrangible line in the protuberance shown on the photograph is due 
to F, and we shall find support of this view in the other fines. In order to determine 
the position of the next fine the dispersive power of the prism was investigated. 
The prism was placed on a goniometer table in minimum deviation for F, and the 
angular distance between F and the hydrogen fine near G, i.e. Hy, was found, as a 
mean of several measurements to be 3'. The goniometer was graduated to 15", 
* Pigs. 5 and 6 show the protuberances as seen on the photographs at the beginning and end of eclipse. 
