Chapman. — On the Peniianency of Solar and Stellar Heat. 97 



photosphere ? If so, the northern parts of the siui would be more affected 

 than the soutliern, for his proper motion has been conckided by various 

 methods to be in north polar declination. 



Should the existence of periodic vertical oscillations in the atmospheres 

 of the earth and sun be demonstrated, then we may be enabled to account 

 for the spots which occur on the planet Jupiter, and the periodicity lately 

 attributed to them ; also, the periodic variability of many of the stars, and 

 even of certain nebulae, H. II 278, and H. I-h 882, for instance, together 

 with the curious alternation of visibility of a star and a connected nebula, 

 as for example 80 " Messier's Catalogue of Nebulae." There have also been 

 cases in which nebulae have only lately made their appearance, and 

 instances of previously well-known nebulae having entirely disappeared, the 

 physical processes of which may be explained by vertical oscillations in 

 elastic masses, which appear to be as universal in elastic media as gravity 

 itself. 



Aet. VI. — On the Permanency of Solar and Stellar Heat. 



By Martin Chapman. 



[Read before the WelliJigton Philosophical Society, 10th October, 1880.] 



A FAVOURITE subject of speculation with physicists is the question of the 



manner in which the heat of the sun and other heavenly bodies of high 



temperature is maintained. 



Various hypotheses are from time to time put forward, supported by 

 speculations of more or less probability. 



Some of these — as, for instance, the ingenious speculations of Mathew 

 Williams ("Fuel of the Sun") — do not appeal to any processes of nature 

 which we can see going on or put to any kind of test. 



Professor Croll assumes the existence of dark, cold masses, whose velocity 

 in space is vastly greater than that of any lucid orb. The collision of these 

 generates heat by the conversion of molar motion. It is to be remarked of 

 this hypothesis that the assumed velocities are such as we can never see on 

 any lucid body ; but Mr. Croll points out that this is only to be expected, as 

 it is only by the destruction of this motion that the bodies can become 

 visible. Such a source of heat would result in this : — that the heat generated 

 would be gradually dissipated, so that the body would gradually cool down 

 and become invisible. 



Most of the received hypotheses assume molar collision of some kind, 



whether of large bodies or of meteoric rain on large bodies, the motion of 



translation being converted into heat. 



13 



