TOTAL ECLIPSE OF THE SUN, APRIL 16, 1893. 
595 
corona lines with slit spectroscopes, but it does not seem improbable that in most 
cases they were produced by prominence light scattered by our atmosphere, as before 
explained—light of which the prismatic camera takes no account. 
Perhaps the most decided evidence in favour of the existence of H and K in the 
corona spectrum is that depending upon the photographs taken with slit spectroscopes 
in 1886; Dr. Schuster states that “the lines end sharply with the corona, and we 
must conclude, therefore, that in spite of the unfavourable atmospheric conditions, 
there was but little light scattered by our own atmosphere in the neighbourhood of 
the sun.” 
But in spite of this observation, Dr. Schuster has concluded that PI and K “ do 
not form part of the normal spectrum of the corona ” f and I may add that the 
prismatic camera strengthens this conclusion. 
The “ Continuous ” Spectrum. 
The photographs taken with the prismatic cameras in 1893 show a pretty strong 
“continuous” spectrum, but it has already been explained that this appearance may 
have been produced by a very complicated spectrum, such as that which I observed 
in the corona in 1882. Concerning my observations, I wrote :—t 
“ Instead of the gradual smooth toning seen, say, in 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.” 
IX. The Variability of the Spectrum of the Corona. 
General Comparison of the 1893 Results with Earlier Observations. 
A change in the spectrum of the corona was placed beyond all doubt in my own 
mind by my observations in 1871 and 1878. With reference to this I wrote as 
follows in 1878 :—J 
“ 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 everybody. Indeed, it is 
remarkable that after all our past study of eclipses this last one should have 
exhibited phenomena the least anticipated. It isolates the matter that gives us the 
continuous spectrum from the other known gaseous 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 
* ‘ Phil. Trans.,’ vol. 180, A, p. 341. 
t ‘ Roy. Soc. Proc.,’ vol. 34, p. 299. 
X 1 Nature,’ vol. 18, p. '460. 
4 G 2 
