Nipher — Primitive Conditions in the Solar Nebula. 121 



the solar mass within the solar volume is therefore immeasur- 

 ably near to unity. The distance from this isothermal to the 

 outer limit of the nebula is a vanishing quantity. The pres- 

 sure at that isothermal is therefore correspondingly small. 

 This result is, in a general way, in harmony with the evidence 

 given by the spectroscope. 



The fineness of the Fraunhofer lines yielded by light from 

 the solar surface, is evidence that the pressure there must be 

 very small. 



It is, however, probable that the real temperature of the 

 sun is much lower than it would be if it had developed from 

 the first as a gaseous nebula. 



Of course the equations of this discussion assume a quies- 

 cent cosmical mass of gas with no external matter. The 

 region around the sun certainly swarms with solid masses 

 which are perhaps in part the remnants of the primitive 

 swarm of meteorites from which the solar system appears to 

 have evolved. These masses when subjected to the fierce 

 radiation from the sun, are perhaps in part vaporized, and 

 their presence must certainly modify the conditions which 

 exist in the region immediately around the sun. The condi- 

 tions at the solar surface are precisely what might be expected 

 if it is being pelted by meteoric matter. 



The temperature of the material composing the various 

 planets of our system has been determined by the heat devel- 

 oped in each by the gravitation of their own masses, after they 

 had separated from the parent mass. 



It should not be understood that the equations of this paper 

 are inconsistent with the existence of gaseous neblae. The 

 reverse is true. It is also probable that more or less of gas may 

 have accompanied the swarm of meteoric masses from which 

 our solar system appears to have been evolved. But it does 

 not seem possible that a planetary system can have developed 

 from a gaseous nebula. 



One of the interesting results of this study, is the high 

 temperatures which pervade the enormous volumes filled by 

 the outer layers of the gaseous nebula where the density and 



