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Sir ISAAC H E W T O NTs Book: I.

which is his second law : and that a body in motion j when itrmeets with another moving* with a greater force; is re-flected without losing any part of its first motion ; but whenit meets with a body moving with less force, it then carries,this body along, and-loses as muchmotion<.as is transferred to it -and this is his third law of nature. He accounts for the hardi-ness of bodies from their parts being quiescent with respect taeach other; and-for fluidity, from-their being moved*perpetuallyin all directions. He concludes the second 1 part of his boosewith telling us, that these principles are sufficient for explainingall the phænomena of nature, and that no other ought to beadmitted or even wished for;

He afterwards proceeds to-{hew how the universe might haveassumed its present form, and- may be for ever preserved, by.mechanical principles. He supposes the particles of matter tohave been angular, so as to replenish space without leavingany interstices between them ; and to have been in perpetualagitations, by which the angular parts being brosee off, theparticles themselves became round, and formed what he callsthe matter of the second element. The angular parts, beingground into the most subtile particles of all, became the matterof his first element, and served to fill all the pores of the other.,But there being more of this first element than was necessaryfor that purpose, it became accumulated in the centers of the‘oortiaesj of which he imagined the universe to confist, and'formed there the bodies of the fun and stars. The heavenswere filled with the matter of the second element, the mediumof light. But the planets and comets consisted of a thirdelement grofler than the other two, the generation of whichhe traces at length through all its steps. According to him,the matter of the first element must have constantly flowed outthrough the interstices between the spherical particles of thei second.