Nipher— The Laiu of Contraction of Gaseous Nebulae. 163 



equation involving a specific heat. It is not the specific heat 

 of the operation, but a specific heat s in a more restricted 

 sense. Let T^ represent the average temperature of the mass 

 M, Then by (48) and (34), 



Replacing T, by its value in (39) and M by its value in 

 (21) 



s== 



(S — 6n) (4 — 371) 2(7 

 3 (2 — n) (5/c — 3) ~J~ 



(50) 



C 

 0.331 ^ 



If there existed a series of nebulae, of various pure gases, 

 like those represented in the last table, we might suppose that 

 they had each advanced to such a stage, that each had the 

 same mass M within a sphere of the same radius, B. Equa- 

 tion (21) asserts that the product CT would then be 

 constant for the series. Those having a larger constant (7, 

 would have a correspondingly smaller temperature T, or T^. 

 This is also the meaning of eq. (50). 



This also follows from equations (19) and (20). Under 

 the conditions just assumed, both P and 3 would be con- 

 stant for the series. As a consequence from eq. (1) the 

 product (7 T must be a constant for all gases. 



To show the extent to which our own sun has, in its last 

 days, of thermal decrepitude, departed from the gaseous 

 condition, we may compare its mass, as computed from eq. 

 (17)', with that obtained from observation. We have for 



hydrogen, C = 4.14 X 10% B = 6.97 X 10^° C7n, j = 



1.54 X 10^, and Tat the surface of the sun may be taken as 

 lOOOO^C. This gives for M the value 1.08 X 10-^« grammes. 

 Taking the mass of the earth at 6.14 X 10^^ grammes, and 

 the mass of the sun as 3.549 X 10^ times that of the earth, 



