166 A NEW SOLAR THEORY. 



But his attention was at the time solel}' directed toward their proba- 

 ble effects on the temperature of our own planet. He found that an 

 increase of absorption by as much as 25 per cent would diminish the 

 mean surface temperature of our globe by 100^ F.. while a like 

 diminution in the solar envelope would produce a corresponding 

 change in the opposite direction. 



Now, if the influence of a change in the a])sorptiYe power of the 

 solar atmosphere is so enormous on a planet at a distance of almost a 

 hundred million of miles, of what inconceivable importance must it 

 not be for the sun itself? Drawing the very natural inference that a 

 deficit of outside radiation means a surplus of energies working upon 

 the solar matter, and vice versa, we are forcibl}^ led to conclude that 

 even slight changes of opacity, such as would elude our must refined 

 observations, are bound to greatly influence the state of thermal equi- 

 librium on our luminary. 



Hence, if changes in the absorptive power of the sun's atmosphere 

 exist, as can not but be the case, the question presents itself: What 

 happens with those energies which, by a condensation of the solar 

 envelope, are prevented from escaping into space? No doul)t the}^ 

 are preserved to the sun, but in what form? Do they raise the tem- 

 perature of the solar mass, or augment its store of potential energy, 

 or have the}' a share in the generation of those marvelous dynamical 

 displays which we perceive in periodic succession on the solar surface? 

 Questions such as these must tend to convince the investigator that a 

 research into the causes of the variability of the forces which we see 

 acting on the sun, if not identical with, is at least ciosely akin to, the 

 investigation of the origin and the physical properties of the sun's 

 atmosphere. 1 shall endeavor in these colunms to demonstrate the 

 possibilit}" of such changes in the densit}' of the solar envelope as 

 would lead to alterations of the thermal conditions of the sun's mass, 

 and shall make an attempt to answer the (juestion as to how far these 

 changes nuist be conducive to variations in the dynamical phenomena 

 at the sun's surface. 



There is perfect unanimity among astronomers as regards the 

 nature of the force which, by a continuous generation of heat, com- 

 pensates for the loss of energy into space. Helmholtz's theory, which 

 attri})utes this heat generation to the progressive contraction of the 

 solar mass as a consequence of gravitation, may be regarded as one of 

 the most probable hypotheses ever propounded in the history of 

 physical science. But this theory does not yet enable us to form an 

 idea of the evolution of a celestial body. It explains the existence of 

 a heat-generating force within the star's bulk, but it gives no answer 

 to the (jucstion as to Avhether the loss of energy bj' radiation is exactly 

 com])ensated for by the generation of energy through contraction, or 

 whether th(> conditions of contraction peculiar to the sun may not 



