130 Mr. W. R. Browne on Action at a Distance. 



redaction of complex facts under simple principles, of parti- ^ 

 cular cases under general laws. The ultimate and most | 

 general principles must therefore be for ever unexplained. 

 Far from its being true that " that which is in itself inex- 

 plicable cannot explain any thing," nothing is fully ex- 

 plained until it has been brought under an inexplicable law. 

 Mr. Tolver Preston fails to recognize that the action of 

 bodies in contact, taken as an ultimate principle, is precisely 

 as inexplicable, as " occult and mystical/'' as the action 

 of bodies at a distance, and that this is perfectly clear to 

 many competent judges. I will cite only one, whose compe- 

 tency no one can deny. Prof. Cayley, in a recent letter to 

 me, remarks: — " My own view has always been that the action 

 of two bodies at a distance presents no greater difficulty than 

 that of two bodies in contact." 



Mr. Tolver Preston suggests that the compression of a bar 

 of iron may be explained by the fact that its molecules are 

 elastic, though he does not suggest any explanation of elasticity 

 under the theory of contact. I have already pointed out, as I 

 did in my first paper, that the question is not about molecules, 

 but about ultimate atoms; and therefore there is no point in 

 the above remark. Beyond this, Mr. Tolver Preston makes 

 no objection to my reasoning, and in the case of magnetism 

 he appears to admit its truth; and yet he demands that the 

 impossibility of action at a distance shall still be admitted. 

 To claim assent to a theory because a certain number of facts 

 may be explained in accordance with it, whilst admitting that 

 there are other facts with which it is at variance, is a proceed- 

 ing which I had hoped was unknown in the domain of pure 

 physics. In that domain progress has only been attained by 

 rigorously rejecting every hypothesis the moment it was shown 

 to be inconsistent with a proved fact; and on this ground I 

 claim the rejection of this particular hypothesis of universal 

 contact action. 



On the side issue as to Le Sage's theory of gravitation, I 

 need only say a word. My remark as to the porosity of 

 matter was independent of the fact whether the spaces left 

 were within the molecules or between them. I was aware 

 that Mr. Tolver Preston had suggested the former; but it 

 makes no difference in the result. With regard to the speed 

 of the gravity-gas particles, I guarded myself by using the 

 words " practically " and " indefinite " from the assertion that 

 it was really infinite. It is sufficient for my purpose that we 

 have no right to put any known superior limit to it what- 

 ever. 



I come lastly to Dr. Lodge, whose note, though imposing 



