THOUGHTS ON THE NATURE AND ORIGIN OF FORCE. 257 



action iTpon the other ivS one which has no parallel or analogue in any 

 other of the known natural forces. In the quasi-magnetic behavior of 

 electrical currents, whatever the vehicle or electrode, occurs a further 

 extension of the same peculiarity. 



ISTotwithstanding all these difficulties, and the intimate relations of 

 "dynamic" with so-called "static electricity," a more comprehensive 

 and rational theory of this most abstruse subject may hereafter establish 

 as radical a distinction between the molecular movements constituting 

 electrical currents, and the molecular capacities of polarity, or of electrical 

 attraction and repulsion, as has been found to exist between light or 

 heat and chemical affinities or molecular repulsions. 



N'or is the inference here suggested affected by the fact that Joule, in 

 1843, derived his first approximation to the mechanical equivalent of 

 heat from experiments "on the calorific effects of magneto-electricity,"* 

 any more than it is by the fact that we accept terrestrial gravity, at the 

 earth's surface, as the standard of comparison for all forms of energy. 



It was seen at the outset that the conditions of antagonistic molecular 

 attraction and repulsion, such as we find in the actual constitution of 

 matter, were essential postulates to the theory of the conservation or 

 persistence of force. We have been led to the conclusion that these 

 same antagonistic principles constitute equally the real, efficient origin 

 of force. And though we are provided with no general term to embrace 

 these primordial, indestructible, immutable, statical centers offeree, and 

 to distinguish them from those other derivative, evanescent, and con- 

 vertible forms of energy, exhibited either in the potential of constrained 

 position, or in the actual of changing position, yet the two classes appear 

 to be so essentially dissimilar that it may well be doubted whether the 

 language very frequently employed by writers to express the correlations 

 and transformations of material forces is really an accurate statement of 

 the fact. 



If it be true that all j)henomena of energy may be traced back ulti- 

 mately to molecular attractions and repulsions as their primeval parents, 

 and if these same attractions and repulsions are found to be persistent, 

 ever-present, and unexchangeable, however fi-equentiy matter in its pro- 

 tean character may be shifted (so to speak) from the active dominion of 

 the one to that of another, it would seem to be exceedingly improbable 

 that, conversely, any form of molecular attraction or repulsion can be 

 produced or derived from motion, or from the ordinary manifestations 

 of dynamic ene-rgy. 



If this be so, we are not warranted in speaking of the correlations of 

 gravity, of cohesion, of chemical affinity, and of magnetism, in the same 

 sense in which we apply the term correlation to the secondary or con- 

 vertible forms of force, as among themselves, and as connected with 

 their primaries. 



* Mr. Joule's paper, read before the British Associatiou, August, 1843, was published in 

 the L. E. D. Phil. Mag. of that year, Vol. XXIII, pages 263, 347, aud 435. 

 17 S 



