XI. On the Radiation of Caloric. By The Reverend Thomas 



Crompton Holland. 



(Read Feb. 7. 1820.J 



JL HE various facts concerning the radiation of caloric pre- 

 sent a very interesting subject of inquiry, and various theories 

 have been formed, with a view to their explanation. The 

 principal difficulty has been to explain the facts of the appa- 

 rent radiation of cold. The most simple theory with respect 

 to these, is that proposed by M. Prevost of Geneva. He sup- 

 poses, that all bodies are always radiating caloric in proportion 

 to their temperature, and that those surfaces, which radiate 

 least, make up for the deficiency, by reflecting most ; so that 

 the combination of reflection and radiation from any surface, 

 when in cequilibrio with the surrounding bodies, is the same. 

 When a body is heated, its radiation is increased, and there- 

 fore, when placed near a thermometer, it radiates more to the 

 thermometer than it receives from it, and therefore elevates its 

 temperature. When, on the other hand, a body is cooled, it 

 intercepts from the thermometer near it part of the radiation 

 of the surrounding objects, and it radiates less than it re- 

 ceives. The thermometer must therefore sink. The princi- 

 pal objections that have been urged against this theory, are de- 



z 2 rived 



