LET. VII. AND DISCOVERIES. I It)

other, without any visible agent, either drawingor impelling them, may be made manifest byvarious instances. The loadstone and a pieceof iron mutually attract each other; two corkballs, swimming in water, approach togetherand meet; and, in electricity, we have num-berless experiments to shew, that several otherbodies have the like propensity to unite and ad-here to each other. These bodies, it is true, actby particular laws, different from that of gra-vity ; but they serve sufficiently well to illustratethe nature of that principle.

But lest these instances should be thought in-sufficient, it may not be amiss to mention a fewothers, which, independent of mathematicaldemonstrations, go near to shew the universalityof this property. Let a circular piece of ice,of two inches and a half in diameter, be weighedagainst any other substance by means of a ba-lance, till they are exactly in equilibrio : underthese circumstances, let the ice be brought totouch the surface of some mercury, contained ina bason below; the ice will be so strongly at-tracted by the mercury, that it will require ninepennyweights eighteen grains, to be put intothe opposite scale, in order to restore the balance.And this adhesion cannot be owing to the pres-lure of the air, for the effect is exactly the samewhen the experiment is performed in vacuo.

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