282 C. A. Young—The Solar Eclipse. 
four instruments. (1.) A spectroscopic camera with diffraction 
had an achromatic lens of three inches aperture and about forty 
inches focus; the slit was about three-fourths of an inch long, 
and so arranged that one-half of it could be uncovered at a 
time, for the purpose of securing the dark lines of the solar 
spectrum as reference marks by a short exposure of one-half 
lens two inches diameter and twenty inches focus. The light 
was concentrated upon the slit by an opera-glass condenser with 
quartz lenses. The whole was equatorially mounted upon a 
ost. With sunlight this instrument gave strong and beauti- 
fully defined impressions of the spectrum from F to O with ex- 
posures of between one-fourth and one-half a second ; but the 
plate exposed through the whole of the totality showed no trace 
of action, to the great disappointment of Mr. W. Libbey, Jr., 
who had charge of the instrument and undoubtedly got from it 
all it would do. 
(2.) A prismatic camera, consisting of a slit, a prism and a 
single quartz lens of ten inches focus. This instrument also 
About eight minutes before totality, the diffraction instrument, 
with a five-second exposure gave a fine spectrum, but neither 
