Dr. J. R. Mayer on Celestial Dynamics. 397, 



formed people, and which will scarcely succumb to correct views, 

 is directly contradicted by the excellent experiments made by 

 Pouiliet at different altitudes with the pyrheliometer. These 

 experiments show that, everything else being equal, the genera- 

 tion of heat by the solar rays is more powerful in higher altitudes 

 than near the surface of our globe, and that consequently a por- 

 tion of these rays is absorbed on their passage through the atmo- 

 sphere. Why, in spite of this partial absorption, the mean tem- 

 perature of low altitudes is nevertheless higher than it is in 

 more elevated positions, is explained by the fact that the atmo- 

 sphere stops to a far greater degree the calorific rays emanating 

 from the earth than it does those from the sun. 



VI. The Constancy of the Sun's Mass. 



Newton, as is well known, considered light to be the emission 

 of luminous particles from the sun. In the continued emission 

 of light this great philosopher saw a cause tending to diminish the 

 solar mass ; and he assumed, in order to make good this loss, 

 comets and other cosmical masses to be continually failing 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 te substance " of light or of heat ; 

 nevertheless, according to it, the radiation of light and heat con- 

 sists also in purely material processes, in a sort of motion, in the 

 vibrations of ponderable resisting substances. Quiescence is 

 darkness and death ; motion 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 particles 

 themselves*; it therefore follows, not only from the emission, 

 but also from the undulatory theory, that radiation continually 

 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 calorific effect of the centrifugal action of the sun can be 

 found by direct observation ; it amounts, according to Chap. 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 



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

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

 Bessel. 



