INTRODUCTION. Ixxxiii 



and returned as the appearance of a flash of 

 lightning, 1 which seems to intimate a constant 

 efflux and influx of inconceivable rapidity. 

 Accordingly the effluxes of light and heat 

 from the solar orb in our own system are never 

 intermitted, and their velocity, for that of light 

 has been measured, exceeds that of any other 

 moving substance. With respect to the fuel, 

 if I may so express myself, that maintains this 

 constant expenditure, little seems yet to be 

 known of it philosophically ; and we can only 

 form conjectures with respect to it derived 

 from the general analogy of nature, as far as 

 it is submitted to the observation of our senses. 

 On earth we know that there can be no com- 

 bustion or evolution of light and heat without 

 the access of air to an ignited body ; and that 

 a constant supply of some combustible sub- 

 stance to replace the constant expenditure of 

 fuel is also necessary. Therefore, reasoning 

 from analogy, something similar must take 

 place at the great focus of light and heat. 

 There must be an influx of air and a supply of 

 combustible matter. That there is such an 

 influx is rendered further probable by other 



1 Ezek. i. 14. 



