l.'U CHEMICAL AFFINITY. 



had recourse, from an opinion long admitted as a first principle, 

 ** that no body can act where it is not," as if it were more diffi- 

 cult to conceive why a change is produced in a body by another 

 which is placed at a great distance, than why it is produced by 

 one which is situated at a small distance. It is not only impos- 

 sible to explain the phenomena of attraction by impulsion, but it 

 is as difficult to conceive how bodies should be urged towards each 

 other by the action of an external substance, as how they should 

 be urged towards each other by a power inherent in themselves. 

 The fact is, that we can neither comprehend the one nor the other; 

 nor can any reason be assigned why the Almighty might not as 

 easily bestow upon matter the power of acting upon matter at a 

 distance, as the power of being acted upon and changed by matter 

 in actual contact. 



But farther, we have no reason for supposing that bodies are 

 ever in any case actually in contact. For a'l bodies are diminished 

 in bulk by cold, that is to say, their particles are brought nearer 

 to each other, which would be impossible, unless they had been at 

 some distance before the application of the cold. Almost all 

 bodies are diminished in bulk by pressure, and consequently their 

 particles are brought nearer each other; and the diminution of 

 bulk is always proportional to the pressure. Newton has shewn, 

 that it required a force of many pounds to bring two glasses within 

 the 800th part of an inch of each other; that a much greater was 

 necessary to diminish that distance; and that no pressure w hit- 

 ever was capable of diminishing it beyond a certain point. Con. 

 sequ< ntly there is a force which opposes the actual contact of 

 bodies ; a force which increases inversely as some power or func- 

 tion of the distance, and which no power whatever is capable of 

 overcoming. Boscovich has demonstrated, that a body in motion 

 communicates part of its motion to another body, before it actually 

 reaches it. Hence we may conclude that, as far as we know, 

 there is no such thing as actual contact in nature, and that bodies 

 of course always act upon each other at a distance. Even impul- 

 sion, therefore, or pressure, is an instance of bodies acting on 

 each other at a distance; and therefore is no belter explanation of 

 attraction than the supposition that it is an inherent power. We 

 must therefore be satisfied with considering attraction as an un- 

 known power, by which all bodies are urged towards each other. 

 It is a power which acts constantly and uniformly, in all times and 



