266 H. Draper—Oxygen in the Sun. 
ahs ese 1, front —s 2, section in plane of narrow opening ; 
ems? i teenies: ¢ c, aperture for rere gases; d, narrow opening 
res ‘spark ; . gee nate prism ; /, slit of spectrosco 
ae 
JAgs 
p A 
() “ve 
a (2) 
6 
DIAGRAM OF PHOTOGRAPHIC PE: a, heliostat mirror; >, spark com- 
SPECTROSCOPE 
parce: ¢, right-angled prism ; a, slit; ¢ collimator; f J, tro bisnphide primes 
g, photographic objective; h, camera; 4, window 
