174 A NEW SOLAR THEORY. 



the validity of the second conclusion, that space receives less heat at 

 the maxima that at the minima of solar activity. 



The solar theory here advanced is based on the assumption that the 

 sun is a "coolinj>-" star, viz, that his contractile force is not sufficient 

 to compensate for his loss of energy b}" radiation. Now strong reasons 

 can be adduced in favor of the assertion that the sun's mass must be 

 mainly gaseous. But it has been urged by astronomers whose opinion 

 on this point may claim earnest consideration, that, in accordance with 

 a well-known theorem first enunciated by Lane, the temperature of a 

 gaseous body should rise through shrinkage. The assumption here 

 advocated would therefore appear to be in opposition to Lane's law. 

 It must be borne in mind, however, that Lane's theorem supposes the 

 conditions of a perfect gas. The question then arises as to whether 

 this perfect state can be assumed to exist in the gaseous bulk of the 

 celestial bodies. To make the question clearl}' intelligible, I shall first 

 have to point out the main difference between the so-called perfect 

 gaseous state and the gaseous state as we actually observe it. On this 

 point 1 ((uote a few passages from Professor Andrews's important 

 treatise in the Philosophical Transactions for 1876, Part II, pages 

 448-41* >: 



1. In the ideal, or, as it is eominonly called, the perfect gaseous state matter would 

 obey implicitly the external forces which act upon it, the vokime being always 

 inversely as the forces externally applied. In this state it would neither offer resist- 

 ance to volume « nor, from the action of internal attractive forces, would it undergo 

 a greater diminution of volume than that due to the external pressure. 



2. In the gaseous state, as we observe it, there are. two distinct causes of internal 

 disturbance whose results are directly opposed, and, according to the nature of the 



gas and the conditions of pressure and temperature, sometimes the one and some- 

 times the other predominates. One of these disturbances is due to the action of 

 internal forces tending to jiroduce a diminution of volume; the other is due to 

 molecular conditions jiroducing a resistance to diminution of volume other than that 

 which occurs in a perfect gas. 



We have, then, to consider three possible conditions: Either the 

 gases in the sun are in that ideal state mentioned under (1), which is 

 characterized ])y the rigorous fulfillment of Boyle's law: or {<() the 

 molecules attract each other and thereby enhance the diminution of 

 volume under increasing pressure; or (h) the molecules repel each 

 other and thereby counteract the diminution of volume. Now, with 

 regard to the attractive molecular forces, the researches of Clausius, 

 van der Waals, and man}^ other physicists, have shown conclusivel}^ 

 that they diminish with increasing temperature. At ordinary tem- 

 peratures all the gases, except hydrogen, show a preponderance 

 of molecular attraction. If the temperature is raised, the mutual 

 attractive influcMice of the molecules becomes smaller, and the gas 



«By resistance to change of volume is to be understood a resistance from internal 

 causes whereliy the gas undergoes a loss diminution of volume under increased pres- 

 sure than would occur in the case of an ideal gas obeying Boyle's law. 



