2(J On Light and Heat, 



of heat from the superincumbent atmosphere, gene- 

 rates a proporiionate degree of cold. Hence the un- 

 comfortable sense of chilliness, so generally complain- 

 ed of, during a sudden thaw. The principle of heat 

 pervades all bodies, and is the immediate cause of 

 fluidity, rarefaction, evaporation, and other important 

 processes. Whether light be essentially different 

 from heat, or only a different modification of the same 

 principle, has not been determined. It is known, 

 however, that when heat is put into a state of rapid 

 motion, its emanations produce light. Whatever 

 may be the essence of light and heat, their presence, 

 as is well known, gladdens all nature, and is indis- 

 pensably necessary to the whole animal and vegetable 

 creation. The grand fountain from which they flow 

 is the sun. Were that glorious luminary extinguish- 

 ed, the animal and vegetable tribes would become 

 torpid, sicken, and die. Even the earth we inhabit, 

 with the surrounding ocean, would partake in the 

 fatal catastrophe, by being soon converted into a mo- 

 nument of ice ! 



Philadelphia, April 2^th, 

 1805. 



