374- Dr. Woods on Chemical Combination. 



repulsions between particles of matter should be altogether dis- 

 missed as, to say the least, unnecessary ; for in all the cases where 

 they are supposed to exist, they must be acting equally and in 

 an opposite direction, so annulling each other. If attraction be 

 imagined to keep the particles of bodies together, an equal re- 

 pulsion must be imagined to counteract the force exactly, or the 

 particles should collapse. And if attraction be said to cause 

 chemical combination, an equal repulsion must at the same time 

 be supposed to act ; for expansion or heat simultaneously occurs. 

 I believe the particles of bodies are perfectly passive with respect 

 to each other, and only move in expansion or contraction, as the 

 opposite movement is at the same time determined by the law 

 of relative volume or distance, as spoken of above. 



I woidd refer for other particulars of the theory I offer to the 

 January Number of the Philosophical Magazine, 1852 ; the 

 present paper contains a mere outline. As I remarked in this 

 paper, that theory pointed out the circumstance that bodies which 

 produced most heat had the greatest affinity, or that, in fact, 

 the heat produced by combination might measure the amount of 

 that affinity, I made some experiments to test the truth of the 

 opinion. In another paper which I submit with this one to the 

 ]\Ieeting, I give the amount of heat which \'arious simple bodies 

 produce with oxygen ; and it will be foimd that those bodies 

 which produce more heat are also capable of taking oxygen from 

 its combination with those producing less ; and that if two bodies 

 be combined, a third will cause their separation if it can produce 

 more heat with either element than the other element does, and 

 will have no effect if otherwise. 



I will briefly sum up my opinions. I conceive that there is a 

 mutual dependence or relation between the space and matter 

 which compose a body ; such relation causing the distance be- 

 tween the particles to be definite. 



That, therefore, if the nature of the matter changes, the di- 

 stance between its particles must also change. 



That if two bodies be mixed or brought together at insensible 

 distances, as in solution, they no longer are two but one body ; 

 and as they were dissimilar previously to being mixed, the one 

 body they form must be dissimilar from either separately, and 

 so the distance between the particles must be different. It must 

 also be less ; for if greater, the bodies could be brought nearer 

 at sensible than insensible distances, and so would not form one 

 body at all, which is contrary to our supposition. But as every 

 molecular movement is accompanied by its opposite, this lessen- 

 ing of distance between combining particles is attended with 

 expansion among others, and this expansion is the heat. 



