COLLISION OF COSMICAL MASSES. 355 



the manner described : calculation teaches us that the amount 

 of heat which would have been evolved in such a case would 

 considerably exceed that which an equal weight of matter 

 could furnish by the most intense process of chemical action. 



It is more than probable that the earth has come into ex- 

 istence in some such way, and that in consequence our sun, as 

 seen from the distance of the fixed stars, exhibited at that 

 epoch a transient burst of light. But what took place in our 

 solar system perhaps millions of years ago, still goes on at 

 the present time here and there among the fixed stars ; and 

 the transient appearance of stars, which in some cases, like 

 the celebrated star of Tycho Brahe, have at first an extraor- 

 dinary degree of brilliance, may be satisfactorily explained 

 by assuming the falling together of previously invisible double 

 stars. 



Contrasting with such explosive bursts of light is the 

 steady radiation, shown continuously through enormous pe- 

 riods, by the greater number of fixed stars, and among them 

 by our sun. Do these appearances, which in so special a 

 manner tempt to higher speculations, constitute a real excep- 

 tion to the exhaustion of a cause in producing its effect, which, 

 in accordance with the foregoing considerations, we have re- 

 garded as an established law of Nature ? or does the small 

 sum of human knowledge authorize us in supposing that here 

 also there is an equivalence between performance and expen- 

 diture, and in searching for the conditions of that equivalent ? 



To enter further upon this subject would lead us beyond 

 the intended scope of this publication ; and I therefore close 

 in the hope that the reader will please to supplement by his 

 own reflection much that in this tract has been left unsaid. 



