THE ELEMENTS. 245 



III. 01' fire, we have said that it dissolves. The only 

 idea probably which this term raised in the reader's mind, 

 was that of fire melting metals, resins, and some other sub- 

 stances, fluxing ores, running glass, and assisting us in many 

 of our operations, chemical or cuhnary. Now these are only 

 uses of an occasional kind, and give us a very imperfect no- 

 tion of what fire does for us. The grand importance of this 

 dissolving power, the great office indeed of fire in the econo- 

 my of nature, is keeping things in a state of solution, that 

 is to say, in a state of fluidity. Were it not for the presence 

 of heat, or of a certain degree of it, all fluids would be frozen. 

 The ocean itself would be a quarry of ice ; universal nature 

 stifi' and dead. 



"We see, therefore, that the elements bear not only a strict 

 relation to the constitution of organized bodies, but a relation 

 to each other. Water could not perform its office to tho 

 earth without air ; nor exist as water, without fire. 



TV. Of light, whether we regard it as of the same sub- 

 stance with fire, or as a different substance, it is altogether 

 superfluous to expatiate upon the use. No man disputes it. 

 The observations, therefore, which I shall ofl^er, respect that 

 little which we seem to know of its constitution. 



Light travels from the sun at the rate of twelve millions 

 of miles in a minute. Urged by such a velocity, with what 

 force must its particles drive against — I will not say the eye, 

 the tenderest of animal substances — but every substance, 

 animate or inanimate, which stands in its way I It might 

 seem to be a force sufficient to shatter to atoms the hard- 

 est bodies. 



How then is this efiect, the consequence of such prodig- 

 ious velocity, guarded against ? By a proportionable mi- 

 nuteness of the particles of which light is composed. It is 

 impossible for the human mind to imagine to itself any thing 

 so small * s a particle of light. But this extreme exility, 

 though difficult to conceive, it is easy to prove. A drop of 

 tallow, expended in the wick of a farthing candle shall send 



