283 



ing to diminish the solar mass ; and he assumed, in order to 

 make good this loss, comets and other cosmical masses to be 

 continually falling into the central body. 



If we express this view of Newton's in the language of 

 the undulatory theory, which is now universally accepted, we 

 obtain the results developed in the preceding pages. It is 

 true that our theory does not accept a peculiar " substance" 

 of light or of heat ; nevertheless, according to it, the radia- 

 tion of light and heat consists also in purely material pro- 

 cesses, in a sort of motion, in the vibrations of ponderable 

 resisting substances. Quiescence is darkness and death ; mo- 

 tion is light and life. 



An undulating motion proceeding from a point or a plane 

 and excited in an unlimited medium, cannot be imagined apart 

 from another simultaneous motion, a translation of the parti- 

 cles themselves ;* it therefore follows, not only from the emis- 

 sion, but also from the undulatory theory, that radiation con- 

 tinually diminishes the mass of the sun. Why, nevertheless, 

 the mass of the sun does not really diminish has already been 

 stated. 



The radiation of the sun is a centrifugal action equivalent 

 to a centripetal motion. 



The caloric effect of the centrifugal action of the sun can 

 be found by direct observation ; it amounts, according to 

 Chapter III., in one minute to 12,650 millions of cubic miles 

 of heat, or 5-17 quadrillions of units of heat. In Chapter 

 IV. it has been shown that one kilogramme of the mass of an 

 asteroid originates from 27'5 to 55 millions of units of heat ; 

 the quantity of cosmical masses, therefore, which falls every 

 minute into the sun amounts to from 94,000 to 188,000 bil- 

 lions of kilogrammes. 



To obtain this remarkable result, we made use of a method 



* This centrifugal motion is perhaps the cause of the repulsion of tho 

 tails on comets when in the neighbourhood of the sun, as observed by 

 BesseL 



