326 MR. J. C. DYER ON THE 



of matter,, to assert the exertion of such invisible moving 

 forces^ as apart from the tangible matter exerting those 

 forces, is clearly a gratuitous assumption, unwarranted by 

 any known properties of material bodies. With respect to 

 the solar rays, we have many striking evidences of their che- 

 mical action in terrestrial phenomena ; but no proof what- 

 ever has yet been adduced to show their mechanical force 

 or action upon tangible bodies, unless their impinging on 

 the optic nerves, giving the sensation of light, may be held 

 to be a mechanical action ; but even if this be so, the force 

 exerted can be but slight. Wherefore these newly disco- 

 vered forces must " vanish into air, into thin air.'"* 



The same high authority (before named) — after giving 

 a brilliant exposition of " the source of the solar rays,^"* 

 or, as it is termed, "the origin and sustentation of 

 the heat of the solar furnace ^^ — and showing how the 

 growth of vegetables depends on the solar influence, and 

 that our stores of coal come from plants, also that by 

 the combustion of coal steam-power is obtained and ma- 

 chinery driven, &c., then adduces the following case, 

 namely : — 



" From machine power we turn to muscular power. 

 Between the steam-engine and living bodies there is the 

 closest analogy. The nutritive materials upon which life 

 depends are no more nor less than combustible substances, 

 which actually undergo a slow combustion. The conversion 

 of food into work done is effected by the same process as 

 that which turns coal or wood into motive force.^^ 



That we must eat to live, and the steam-engine must 

 have steam to work it, are simple facts that require no 

 comment; but the forces exerted to sustain the move- 

 ments of a metallic engine, and the living organisms, are 

 so widely different in the two cases, that one could hardly 

 expect to see their close analogy asserted by any writer 

 on the laws of physics, except under strange illusions 



