332 
CAPTAIN" L. DARWIN", DR. A. SCHUSTER, AN"D MR. E. W. MAUNDER 
before the .eclipse, is not imaginary, is shown by the failnre of the Carriacou 
photographs. 
Tn the present instance the hydrogen lines Hy, Ji, and those in the ultra-violet, 
appear in the prominence spectrum as well as H and K, and "they give us sufficient 
data to determine the wave-lengths of the lines which appear in the spectrum of the 
corona. The measurements were taken by means of a dividing machine reading 
to '002 mm. The following Table gives in centimeters the distance of three of the 
hydrogen lines from B, as measured on the reference spectrum and on the spectrum 
taken during the eclipse. 
Eeference spectrum. 
Eclipse spectrum. 
h 
•3187 
•3184 
H'/ 
•7943 
•7930 
F 
l-o362 
1-5382 
h and Hy appear as prominence lines, and their distances from H are practically the 
same on the two plates. About F there is more doubt. There is a faint mark on the 
eclipse spectrum which I had originally taken to be the image of the prominence 
which I expected to find there, but which may easily be an accidental spot on the 
photograph. The distance of this spot from H is 1‘54.30 or the tenth part of a 
millimetre further than F. The discrepancy seemed to me to be too great, and on 
examining the photograph again I found on the more refrangible side of the spot a 
distinct absorption line, which, when measimed, gave 1'5382 as distance from H. 
Considering the faintness of the image near F, the measurement seemed now to 
agree, as well as could be expected, with the reference spectrum, on the supposition 
that F shows as an absorption line in the corona. I conclude, therefore, that the 
distance of a given line from H on the eclipse plate is the same as that of a 
corresponding line on the reference plate. In order to find the wave-lengths of the 
lines in the corona I proceeded as follows. 
The distances of the following lines were carefully measured on the reference 
spectrum from H :— 
Fe.. . 4004-9 
Fe . 4045-1 
h ..4101-2 
Ca. 4226-4 
Hy. 4340-1 
Fe. 4666-5 
F. 4860-7 
