124 CORRELATION OF PHYSICAL FORCES. 



philosopher of high repute, I cannot see the force of the 

 arguments by which it has been assailed ; and therefore, for 

 the present, though with diffidence, I still adhere to it. The 

 fact itself of the correlation of the different modes of force is 

 to my mind a very cogent argument in favour of their being 

 affections of the same matter ; and though electricity, magnet- 

 ism, and heat might be viewed as produced by undulations of 

 the same ether as that by means of which light is supposed to 

 be produced, yet this hypothesis offers greater difficulties with 

 regard to the other affections than with regard to light : many 

 of these difficulties I have already alluded to when treating of 

 electricity ; thus conduction and non-conduction are not ex- 

 plained by it ; the transmission of electricity through long 

 wires in preference to the air which surrounds them, and 

 which must be at least equally pervaded by tlu- ether, is 

 irreconcilable with such an hypothesis. The phenomena ex- 

 hibited by these forces afford, as I think, equally strong evi- 

 dence with those of light, of ordinary matter acting from par- 

 ticle to particle, and having no action at a distance. I have 

 already instanced the experiments of Faraday on electrical 

 induction, showing it to be an action of contiguous particles, 

 which are strongly in favour of this view, and many experi- 

 ments which I have made on the voltaic arc, some of which 

 I have mentioned in this Essay, are, to my mind, confirma- 

 tory of it. 



If it be admitted that one of the so-called imponderables is 

 a mode of motion, then the fact of its being able to produce 

 the others, and be produced by them, renders it highly diffi- 

 cult to conceive some as molecular motions and others as 

 fluids or undulations of an ether. To the main objection of 

 Dr. Young, that all bodies would have the properties of solar 

 phosphorus if light consisted in the undulations of ordinary 

 matter, it may be answered that so many bodies have this 

 property, and with so great a variety in its duration, that 

 non constat all may not have it, though for a time so short 



