460 JVipher — Gravitation in Gaseous Nebulae. 



The equations show that the same pressures and densities 

 would hold for any other perfect gas. In fact, the above equa- 

 tion shows that if r and M are fixed, the product TC must be 

 constant for all gases. This carries with it the conclusion 

 shown by the other equations, that the average density of such 

 a solar mass is independent of the nature of the gas. This is 

 a matter of great significance, when taken in connection with 

 the fact that the real density of the sun is only slightly greater 

 than the density of the hypothetical hydrogen sun. 



The real condition around our sun is, that increasing opacity 

 to radiation as one goes to levels of smaller radius, has retained 

 the heat within the dense nucleus. The rarefied external parts 

 of the solar nebula have parted with their heat and the tem- 

 perature throughout the mass has ceased to be uniform. Inter- 

 planetary pressures have been abolished. Hydrogen would 

 solidify at a distance of 92 million miles from our sun if away 

 from any large mass of matter. And this obliteration of cos- 

 mical pressure has almost wholly compensated the fall in tem- 

 perature of the sun from 20 millions at least to perhaps 

 10,000 degrees. 



The fact that a gaseous mass can apparently contract itself, 

 and heat up in some such way as it would do if it were com- 

 pressed by the action of some external system, is obviously of 

 profound significance. The clue that it seems to give concern- 

 ing the nature of gravitation is well worthy of the most serious 

 attention. Is not gravitation the action upon matter of a 

 system wholly external to matter ? 



