214 THE ELEMENTS. 



may proportionably support as many inhabitants ; minister 

 to as large an aggregate of enjoyment. The land only af- 

 fords a habitable surface ; the sea is habitable to a great 

 depth. 



III. Of 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 

 substances, fluxing ores, running glass, and assisting us in 

 many of our operations, chemical or culinary. Now these 

 are only uses of an occasional kind, and give us a very 

 imperfect notion of what fire does for us. The grand im- 

 portance of this dissolving power, the great office indeed of 

 fire in the economy 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 quar- 

 ry of ice ; universal nature stiff" 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 of- 

 fice to the earth without air ; nor exist as water, without fire. 



IV. Of LIGHT, (whether we regard it as of the same 

 substance with fire, or as a different substance,) it is alto- 

 gether superfluous to expatiate upon the use. No man dis- 

 putes it. The observations, therefore, which I shall offer, 

 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 

 wh3.t force must its particles drive against, I will not say 

 the eye, the tenderest of animal substances, but every sub- 

 stance, animate or inanimate, which stands in its way ? It 

 might seem to be a force sufficient to shatter to atoms the 

 hardest bodies. 



How then is this effect, the consequence of such prodi- 

 gious velocity guarded against ? By a proportionable mi- 

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

 impossible for the human mind to imagine to itself any 

 thing so small as a particle of light. But this extreme ex- 

 ility, though difficult to conceive, is easy to prove. A drop 

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

 shed forth rays sufficient to fill a hemisphere of a mile di- 

 ameter ; and to fill it so full of these rays, that an aperture 

 not larger than the pupil of an eye, wherever it be placed 

 within the hemisphere, shall be sure to receive some of 

 them. What floods of light are continually poured from 



