CALORIFICATION, 355 



them, in its turn, fall upon the bulb of a ther- 

 mometer, near which two others were placed to 

 serve as standards : the number of degrees, 

 which a thermometer, exposed to the colored 

 ray, rose above the other two, indicated the 

 heating power of that ray, he found that the 

 thermometer, which was either naked, or 

 whitened with paint, was lower than the one 

 which was blackened and that the white 

 thermometer, w r hen exposed to the red ray, 

 rose from 55 to 58-3 degrees* The black ther- 

 mometer, exposed to the same ray, rose from 

 58 to 61. The same thermometer, exposed to 

 the dark ray, rose in a greater proportion; 

 while the former scarcely rose one half degree, 

 the latter rose from 59 to 64. It is not surpri- 

 sing that Dr. Herschell should express his 

 astonishment at finding that the illuminating 

 and heating power of the rays, follow such dif- 

 ferent laws. According to the present doc- 

 trine of fire, this difference is altogether inex- 

 plicable; but according to the principles which 

 I have endeavoured to develope, they are the 

 effect naturally flowing from cause. We 

 find the colored, and, consequently, the com- 

 bined rays of the sun produce heat ; they pro- 

 duce heat because they are combined, and they 

 are combined, because they are found to excite 

 the sensation of heat. The degree of heat these 

 rays are found to excite, will always depend on 

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