TEMPERATURE AND STRUCTURE OF THE SUN. 
91 
far as they emit a line spectrum, is caused by luminescence 
and not by high temperature only. 
Since we do not know whether the sun’s radiation is that 
ol a black body or that of bright platinum, it is fortunate 
that we have a better method of estimating the temperature 
ot the sun from its total radiation. According to the 
Stefan-Boltzmann law, we have 
where Si and S 2 are the total energies radiated by a black body 
at the absolute temperatures and T 2 . Thus we have 
s l -s t = a,(T*- r 2 4 ) 
and according to Kurlbaum’s observations, 
S. m - S m = 0.01763 
gr. cals. 
cm. 2 sec. 
Thus we get 
a — 
0.01763 
373 4 — 273 4 
1.28 x 10 
gr. cals. 
cm. 2 sec. 
Earth 
Fig-3. 
Let us now assume the sun to be a black body. A black hemis- 
phere at the temperature 7 T s radiates per second to a unit of sur- 
face of our earth at the temperature !]., the energy 
S\ 
s e 
1.28X10 
gr. cals. 
J e / 2 
cm. sec. 
14— Bull. Phil. Soc., Wash., Vol. 15. 
