H. Draper—The Solar Eclipse. 229 
In order to have every chance of success it is necessary to pro- 
cure a lens of large aperture and the shortest attainable focal 
length, and to have a grating of the largest size adjusted in 
such a way as to utilize the beam of light to the best advan- 
tage. Moreover, the apparatus must be mounted equatorially 
and driven by clockwork so that the exposure may last the 
whole time of totality and the photographic work mus: 
done by the most sensitive wet process. After some experi- 
ments during the summer of 1877 and the spring of 1878, the 
following form was adopted. 
he lens being of six inches aperture and twenty-one inches 
focal length, gave an image of the sun less than one-quarter of 
an inch in diameter and of extreme brilliancy. Before the 
beam of light from the lens reached a focus it was intercepted 
by the Rutherfurd grating set at an angle of sixty degrees. 
This threw the beam on one side and produced there three 
images—a central one of the Sun and on either side of it a 
spectrum [ should have procured ring-shaped 
for each bright line. On the other hand, if the light of the 
corona arose from incandescent solid or liquid bodies or was 
reflected light from the Sun I was certain to obtain a long band 
in my photograph answering to the actinic region of the spec- 
trum. If the light was partly from gas and partly from re- 
flected sunlight a result partly of rings and partly a b 
would have appear 
Immediately after the totality was over and on developing 
the photographs, I found that the spectrum photographs were 
continuous bands without the least trace of a ring. I was not 
surprised at this result because during the totality I had the 
Opportunity of studying the corona through a telescope 
arranged in substantially the same way as the photo-telespec- 
troscope and saw no sign of a ring. d 
The plain photograph of the corona taken with my large 
equatorial on this occasion shows that the corona is not 
rom the sun toward the west while it was scarcely a degree in 
length toward the east. The mass of meteors, if such the 
Construction of the corona, is therefore probably arranged in 
an elliptical form round the sun. ; 
