Constancy of Solar Light and Heat. 129 



to which, is attached a conical cup containing* different lead 

 weights, ranging from half an ounce to 36 pounds. According 

 to the force of the wind these weights are raised, and the 

 pencil marks the exact weight lifted up. 



The "Atmospheric Recorder" and many other meteoro- 

 logical instruments were presented to me by Mr. Henry Lawson, 

 and are now doing me good service at the Beeston Observatory. 



CONSTANCY OF SOLAE LIGHT AND HEAT. 



BY ALEXANDER S. HERSCHEL, B.A. 



Those who admit no waste of power in the different opera- 

 tions of the energies of nature must encounter the difficult 

 question of the maintenance of a constant source of light 

 and heat upon the surface of the sun. The sun constantly 

 delivers to the earth, in heat alone, an energy equal to the hun- 

 dredth part of that force by which it constantly draws tho 

 earth into a spiral path about itself. This is but the two thou- 

 sand millionth part of the total heat, or energy, which the sun 

 continually develops and dismisses into space ; yet the efflux 

 is unabated, and has apparently remained the same from the 

 earliest historic ages, and from, the remotest ages of geology, 

 to the present time. 



Misled by the almost fabulous scale of this outlay, some have 

 attempted to persuade themselves that a new theory of solar 

 radiation might prove the estimate to be overdrawn. They 

 propose to consider that solar heat, like gravity, is imparted 

 only to surrounding objects, by a species of reciprocation, or 

 by a sympathetic interchange between the sun and other 

 bodies • and that it is the part of surrounding bodies to disperse 

 the solar heat into space under the usual laws of radiation 

 and in the ordinary form of radiant heat : did they not do so, 

 that these bodies and the sun would reach an equilibrium of 

 temperature by an interchange of heat, and would maintain it 

 unabated to the end of time. 



This theory, in itself incredible, makes it yet apparent that 

 if a reasonable explanation could be given of the constancy of 

 solar light and heat it would be accepted, by analogy, as a 

 step towards the better understanding of the great law of 

 Newton — that one particle constantly attracts another in pro- 

 portion to its mass. 



The sun as a merely heated body would fall in temperature 

 and lose its light sensibly in the course of a small number of 

 years, or even months. This temperature docs not appear 

 greatly to exceed that of the electric arc, but it remains un- 



