252 THOUGHTS ON THE NATURE AND ORIGIN OF FORCE, 



or interference; the total resultant of wliose impacts on gross matter 

 constituted gravitation. A single particle or mass of matter equally 

 inii)ressed on all sides by these universal projectiles would, of course, re- 

 main in perfect equilibrium. But two or more such bodies in space, 

 screening each other on their facing sides, would be subjected to un- 

 balanced imx^acts from these infinitely minute but powerful " corpuscles," 

 and would tbus be always urged toward each other in the directions 

 joining their centers. No explanation of the origin of the enormous 

 living force assumed in these winged motes was attempted. Although 

 the law of the inverse square of the distance could be mathematically 

 deduced from the assumption, the law of mass ratio was unfortunately 

 not so well represented by it. 



Sir John Herschel remarks upon this abstract speculation : " The 

 hypothesis of Le Sage, which assumes that every jioint of space is pene- 

 trated at every instant of time by material particles, sui generis^ moving 

 in right lines in every possible direction, and impinging upon the material 

 atoms of bodies, as a mode of accounting for gravitation, is too grotesque 

 to need serious consideration ; and besides will render no account of the 

 phenomenon of elasticity"* 



More recent speculators have supposed that motion explains every- 

 thing ; and they accordingly suggest the probability that all force — in- 

 cluding gravitation — is a form of vibration. Observing the remarkable 

 extension of the undulatory theory, first to light, and subsequently to 

 heat, and perhaps mindful of the radiant law of diminution with the 

 square of distance, they seem to have been led from this analogy) to 

 overlook the consideration that no vibration is possible without two 

 oi^posing forces ; and so in substitution or in explanation of that which 

 is itself simple they proffer a duplex causation. All such hypotheses 

 have been projected under the impulse of the ancient a priori dogma, 

 that "matter cannot act where it is not," or of the equivalent proposi- 

 tion, that action upon a distant body is " inconceivable ! "t 



Professor Faraday entertained a somewhat indefinite idea (borrowed 

 from Boscovich's abstract centers of force) that matter must be contin- 

 uous, or everywhere present, in order that forces may be transmitted 

 by virtual contact. He says : " Doubtless the centers of force vary in 

 their distance one from another, but that which is truly the matter of 



*'' On the Origin of Force." Fortnightly Review, Vol. I, p. 438. 



t It may be asserted in reply to tliis, that no scientific theory is final until its ultimate 

 jiostulate is " inconceivable." " For if the successively deeper interpretations of nature 

 ■which constitute advancing kno\yledge are merelj' successive inclusions of special 

 truths in general truths, and of general truths in truths still more general, it obviously 

 follows that the most general truth, not admitting of inclusion in any other, does not 

 admit of interpretation. Manifestly as the most general cognition at which we arrive 

 cannot be reduced to a more general one, it cannot be understood. Of necessity, there- 

 fore, explanation must eventually bring us down to the inexplicable. The deepest truth 

 which Ave can got at must be unaccountable." Herbert Spencer, First PrincipJes, 

 (second edition,) Part I, Chap. IV, p. 73. 



