272 CALORIC THE ACTIVE PRINCIPLE IN LIGHT. 



That caloric is the active principle in solar 

 light would appear from the fact, that the quan- 

 tity of light produced by ordinary combustion, 

 c&teris paribus, is always in proportion to tempe- 

 rature ; and it will be shewn hereafter, that 

 without caloric there could be no electricity nor 

 light. 



Newton maintained that light and common 

 matter were mutually convertible into each 

 other ; but seems not to have inquired whether 

 solar radiation was connected with the planetary 

 movements. So far was he from recognizing the 

 agency of the sun's heat in maintaining the life 

 of nature, that when speculating on the use of 

 comets, he hints that they may be wandering 

 magazines of vitality, which they distribute to 

 the planets, thus supplying its consumption by 

 vegetable and animal growth. 



Such is the love of mankind for the mar- 

 vellous, that the most obvious causes of natural 

 phenomena are disregarded, and their explana- 

 tion sought after by resorting to such as are 

 hypothetical and remote, or obscure. Hence it 

 is, that our books on Natural Philosophy are 

 filled with speculations about the vacuum of 

 space, while visible and palpable floods of lu- 

 minous tether are continually pouring upon the 

 earth from the great fountain of physical motion 

 and life. When Sir H. Davy observed, that it 

 " was absolutely necessary for the explanation 



