Physical Constitution of the Sun. 291 



The empiric hypotheses were : — 



1. The numerical value of that ratio of the specific heats ; 



2. The numerical value of the pressure of the hydrogen 



atmosphere at a definite height above the glowing 

 liquid surface of the sun ; 



3. The numerical value of this definite height ; 



4. The density of the masses of hydrogen compressed in 



the interior of the sun, and breaking forth at its sur- 

 face in the form of eruptive protuberances. 



It is obvious that, the less the number of the hypotheses de- 

 manded by a method for the determination of physical proper- 

 ties of the sun on the basis of terrestrial units of measurement, 

 the more probable will be the results it must furnish. I there- 

 fore take leave to communicate in the following a considerably 

 more simple method for the determination of the temperature of 

 the atmosphere of the sun — a method which for its employment 

 requires, as a theoretical hypothesis, only the law of Mariotte 

 and Gay-Lussac, and as an empiric presupposition only the 

 knowledge of the density-ratio which subsists in two strata, at 

 different altitudes, of the hydrogen atmosphere, the distance of 

 which is known. 



Let, namely, 



h denote the distance of the two strata, 

 0-j the density in the lower stratum, 

 c- 2 the density in the upper stratum, 



r the distance of the lower stratum from the centre of the sun, 

 g the intensity of gravity in the lower stratum, 

 u the coefficient of expansion of the gases at 1° C, 

 a a constant, dependent on the nature of the atmospheric gas, 

 t the absolute temperature of the atmosphere under consi- 

 deration ; 



then, as is well known, in the state of equilibrium, and presup- 

 posing a constant temperature, the following relation subsists 

 between the above eight quantities : — 



lognat . -> = !!:.* a, 



o- 2 aod r + h 

 Putting herein 



lognat. — =/, 

 there follows as the expression for the absolute temperature : — ■ 



aa.1 r + ti v ' 



X 2 



