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ASTRONOMY: H. SHAPLEY 
The variability of the light of the seventh magnitude star RR Lyrae, 
the brightest of the cluster-type sub-class of the Cepheid variables, was 
discovered at Harvard seventeen years ago by the unique method of 
setting a special automatic photographic telescope to follow the star 
throughout the night and make a continuous and permanent record of 
its light. Due to the brightness of the variable and its importance in 
connection with the study of stellar variation, it has received wide- 
HOURS 
-3 0 +3 +6 +9 
— I — T — r- — r — r 
1.6 - 
I I I I I 1 1 
FIG. 1. TOP: MEAN VISUAL LIGHT-CURVE OF RR LYRAE (OBSERVATIONS BY WENDELL) 
AND VARIATION OF SPECTRUM (SHAPLEY). 
BOTTOM: PHOTOGRAPHIC LIGHT-CURVE OF RS BOOTIS (SEARES AND SHAPLEY) AND 
VARIATION OF SPECTRUM (PEASE). 
spread attention. The light variations have been observed at Harvard, 
Princeton, the Lick Observatory, the University of Missouri, and at 
observatories in Italy, Germany, Sweden, and Ireland. Special measures 
of its position have been made in Finland and in Germany, and obser- 
vations of the spectrum at Harvard, Lick, and Mount Wilson. 
Kiess at the Lick Observatory found the star to be a radial-velocity 
variable — a spectroscopic binary of the peculiar Cepheid type. This 
