sufficiently, seems to extend itself into the boundaries of the others, and, as it were, to enclose and comprehend them all. Thus magnetism mixes itself with the gravitation both of bodies upon the surface of the earth, and with that of the moon to the earth: a polar virtue of the same kind seems to have a principal share in the formation of natural bodies, especially those whose parts cohere in regular figures: electricity may also extend, without being excited by friction or otherwise, to small distances, and join with the just-mentioned polar virtue in making the parts of bodies cohere, and in some cases in regular figures. The effervescence which attends the mixture of acids and alcalis, and the solution of certain bodies in menstruums, fermentation, and putrefaction, are all general principles of very extensive influence, nearly related to each other, and to the fore-mentioned mutual attractions and repulsions, and are possessed of the same unlimited power of propagating themselves, which belongs to the several species of plants and animals. A repulsion which should throw off indefinitely small corpuscles with indefinitely great velocity from all the bodies of the universe, (a thing that would be very analogous to the emission of light, odoriferous particles, and magnetical and electrical effluvia, and to the generation of air and vapour,) might cause the gravitation of all the great bodies of the universe to each other, and perhaps other kinds of attraction. Some of these corpuscles, by stopping each other in the intermundane spaces, or other mutually repulsive corpuscles lodged there from causes not yet discovered, may compose a subtle vibrating medium. The vibrations of this medium, being continued to the great bodies of the universe, may so far agitate their small parts, as to give their attractive and repulsive powers an opportunity to exert themselves with great vigour; and the emission of the above-mentioned corpuscles may be, in part, occasioned by the attractions and consequent collisions of small parts thus agitated; so that elastic corpuscles may be thrown off from these small parts with indefinitely great velocity. And it would be no objection to these or such like suppositions, that we could not explain, in any definite manner, how these things are affected, nor put any limits to the sizes of decreasing corpuscles, or their active powers in respect of each other. Nor would this be to reason in a circle, more than when we argue, that the heart and brain, or the body and the mind, depend upon each other for their functions; which are undeniable truths, however unable we may be to give a full and ultimate explanation of them. However it is not impossible, on the other hand, but future ages may analyse all the actions of bodies upon each other, up to a few simple principles, by making such suppositions as the phænomena shall suggest, and then trying and modelling them by the phænomena. At least this is what one is led to hope, from the many simple and easy solutions of very complex problems, which have been produced within the two last centuries.
