176 A NEW SOLAR THEORY. 



the ussiiniption of their representing real di.sphicement of matter. It 

 has been urged that the speed with which matter can ))e thrown up 

 can not exceed the velocity of sound. l)ut that the maximum speed 

 which can he reasonabh' assigned to the propagation of sound in the 

 incandescent gases at the sun's surface falls considerably short of the 

 velocities observed in solar prominences. Here, however, we must 

 again bear in mind that the computed velocities of sound which have 

 been used as an argument against the eruption theory are based 

 entirely on Boyle's law. If repulsive molecular forces are taken into 

 consideration, the velocity of sound appears to Ijc greater than in the 

 case of a perfect gas. In fact, it is then no longer possible to assign 

 an upper limit to the velocity of the sound wave, and hence this argu- 

 ment against the reality of the displacement of matter in solar erup- 

 tions loses its force. 



As I shall demonstrate in my paper, a careful investigation of the 

 behavior of gases at such temperatures as we may obtain in oui' lab- 

 oratories, points conclusively to the fact that at solar temperatures 

 gaseous matter must be far from the ideal state to which Boyle's law 

 ref(U"s. Many of our views, hitherto based on this law, may have to 

 be altered, Init the changed aspect only removes serious difficulties 

 without introducing others. I have found it advisable to add these 

 few remarks on the state of gaseous matter in the sun to the original 

 text of my investigation, as printed in Nature, February 13, 1902, in 

 order to show briefly that the assumption upon which this solar theory 

 mainl\' depends, viz, that our sun belongs to the class of "cooling'" 

 stars, is reconcilable with the gaseous constitution of his mass. 



