528 
PHYSICS: J. T. HOWELL 
with surface temperatures but half as much. But the Kght emission 
per unit area is much less for red stars than for blue. The obvious 
conclusion is, therefore, that in all these clusters, and probably in all 
globular clusters, the volumes of the bright red stars are very great in 
comparison with the stars that are fainter and relatively blue. 
^ These Proceedings, 2, 12 (1916). 
Mi. Wilson Contr., No. 116, Sections IV and VIII (1916). 
3 Puhl. Astr. Soc. Pac, No. 163, April 1916. 
THE EFFECT OF AN ELECTRIC FIELD ON THE LINES 
OF LITHIUM AND CALCIUM 
By Janet T. Howell 
MOUNT WILSON SOLAR OBSERVATORY, CARNEGIE INSTITUTION OF WASHINGTON 
Received by the Academy. August 10, 1916 
During the last three years a great deal of work has been done on the 
electric decomposition of spectral lines. Stark^ examined the effect 
in canal rays, subjected to a strong auxiliary field, and Lo Surdo^ photo- 
graphed the light immediately in front of the cathode, where the lum- 
inosity of the negative glow and the sudden fall of potential fulfilled 
the required conditions. Hydrogen and helium have been examined 
by both methods and Stark has investigated the transverse effects for 
lithium, mercury, and a number of other elements. So far, only H, 
He, and Li have shown large effects, and the results found for H and He 
by the two methods differ considerably. 
In spite of the great number of data accumulated by Stark, Lo Surdo, 
and their co-workers since the discovery of the electric effect, the work in 
this important field is only begun and offers great opportunities for 
further work. The apparatus used by Stark is very difficult to con- 
struct and needs the constant services of a skilled glass blower. More- 
over, Stark has already examined most of the more promising elements. 
The method of Lo Surdo is very simple and has been applied, so far, 
only to hydrogen and helium. A survey of a number of elements was 
therefore made with the Lo Surdo form of apparatus, under low dis- 
persion, and in the course of the work some new and interesting results 
were obtained with calcium and lithium. 
A full description of the apparatus used will be published in the 
Astro physical Journal, but it was essentially of the Lo Surdo form. The 
tube had an internal diameter of 6 mm. and a length of 20 cm. The 
discharge from an induction coil was used, rectified by a valve tube. 
The spectrum was photographed with a three prism, quartz and ultra- 
