FORCE, A CAUSE OF MOTION. 17 



the phenomena, arising out of the mechanical force 

 applied to the particle first moved.* This mechanical 

 force, it must be remembered, is external to the body 

 moved, and is, in all probability, set up by the move- 

 ment of a muscle, acted upon by nerves, under the 

 influence of a will. 



The series of phenomena we have supposed to arise 

 admit of an explanation free of the hypothesis of motion, 

 and we avoid the dangerous ground of metaphysical 

 speculation, and the subtleties of that logic which rests 

 upon the immateriality of all creation. This explanation, it 

 is freely admitted, is incomplete : we cannot distinctly 

 correlate each feature of the phenomena, combine link 

 to link, and thus form a perfect chain ; but it is suffi- 

 ciently clear to exhibit what we do know, and leave the 

 unknown free for unbiassed investigation. 



Each particle, each atom of that which conveys to our 

 senses the only ideas we have of natural objects pon- 

 derable matter is involved in, or interpenetrated by, 

 those principles which we call heat and electricity, with 

 probably many others which are unknown to us ; and 

 although these principles or powers are, according to 

 some law, bound in statical equilibrium to inert matter, 

 they are freely developed by an external excitement, and 

 the disturbance of any one of them, upsetting the equili- 

 brium, leaves the other power equally free to be brought 

 under the cognizance of human sense by their effects. 



When we come to an examination of the influences 

 exerted by these powers upon the physical earth, the 

 position, that they must be regarded as the causes of 

 motion rather than the effects of it, will be further con- 

 sidered. At present it is only necessary to state thus 



* Friction, it is well known, generates heat ; by rapidly rubbing 

 two sticks together, the Indian produces their ignition ; heat and 

 light being both manifested. Under every mschanieal disturb- 

 ance electrical changes can be detected, and the action of heat in 

 the combustion of the wood is a chemical phenomenon. 



c 



