50 
ASTRONOMY: W. W. COBLENTZ 
Proc. N. a. S. 
In view of the fact that his continuous spectrum measurements terminated 
at 0.42 ju, where also is the observed maximum spectral energy, it is pos- 
sible that the higher estimated temperature is the more nearly correct. 
Wilsing, Scheiner and Miinch (loc. cit.) also obtained a temperature 
of 6800° K for 7 Cassiopeiae. Their temperature measurements of va- 
rious stars of class B vary from 7000° to 15,000° K; class A, from 8000° to 
12,000° K; class F from 5000 to 7000° K; class G, from 4000 to 5000° K; 
and class M, 3000° to 3500° K. 
While it is to be expected that the various methods must give different 
results, it is interesting to find a rather close agreement in the estimated 
stellar temperatures. The agreement is especially close for stars of classes 
G, K and M, that is, stars having a low temperature. 
In a previous paper, data were given on a comparison of stellar radiom- 
eters and radiometric measurements of 110 stars using the Crossley 
reflector of the Lick Observatory at Mt. Hamilton, Calif., the altitude 
being about 4000 ft. Quantitative measurements were made on stars 
down to magnitude 5.3, and qualitative measurements to magnitude 6.7. 
It was found that red stars emit from 2.5 to 3 times as much total radiation 
as blue stars of the same visual magnitude. 
These observations were verified by an independent method which con- 
sisted in measuring the transmission of stellar radiation through a 1 -cm. 
cell of water, having quartz windows. By this means it was shown that 
of the total radiation emitted, blue stars have about 2 times as much 
visible radiation as yellow stars and about 3 times as much visible radiation 
as red stars. 
2. Experimental Procedure. — In the present investigation the spectral 
energy distribution of a star was determined by means of a series of trans- 
mission screens, placed in front of a vacuum thermocouple which was 
used as the radiometer. 
Screens were selected which, either singly or in combination, had a 
uniformly high transmission over a fairly narrow region of the spectrum 
terminating abruptly in complete opacity in the rest of the spectrum. 
By proceeding in this manner the observations required no correction 
other than that for surface reflection, which amounts to about 9 per cent 
for the two surfaces of the screen. Corrections were made for absorption 
by the telescope mirrors, also for atmospheric absorption, using the spec- 
tral transmission factors for the sun, as observed by Abbot and Fowle. 
By means of these screens (of red and yellow glass, quartz and water) 
it was possible to obtain the radiation intensity in the spectrum (from the 
extreme ultra-violet, which is limited by atmospheric transmission and 
the low reflectivity of the telescope mirrors) at 0.3 ju to 0.43 /x; 0.43 /x to 
0.60m; 0.60m to 1.4ju; 1.4m to 4.1m; and4.lM to 10m. 
In this manner the distribution of energy in the spectra of 16 stars was 
