Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/30

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That the attractive virtue of the Sun is propagated on all ides to prodigious ditances, and is diffued to every part of the wide pace that urrounds it, is mot evidently hewn by the motion of the Comets; which coming from places immenely ditant from the Sun, approach very near to it; and ometimes o near, that in their perihelia they almot touch its body. The theory of thee bodies was altogether unknown to atronomers, till in our own times our excellent author mot happily dicovered it, and demontrated the truth of it by mot certain obervations. So that it is now apparent that the Comets move in conic ections having their foci in the Sun's centre, and by radii drawn to the Sun decribe areas proportional to the times. But from thee phænomena it is manifet, and mathematically demontrated, that thoe forces, by which the Comets are retained in their orbits, repect the Sun, and are reciprocally proportional to the quares of the ditances from its centre. Therefore the Comets gravitate towards the Sun; and therefore the attractive force of the Sun not only acts on the bodies of the Planets, placed at given ditances and very nearly in the ame plane, but reaches alo to the Comets in the mot different parts of the heavens, and at the mot different ditances. This therefore is the nature of gravitating bodies, to propagate their force at all ditances to all other gravitating bodies. But from thence it follows that all the Planets and Comets attract each other mutually, and gravitate mutually towards each other; which is alo confirmed by the perturbation of Jupiter and Saturn, oberved by atronomers, which is caued by the mutual actions of thee two Planets upon each other; Rh