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G. Galilæus, his Systeme.
use, in the ordinate parts of the World; and we did proceed to say, that it was not so in circular motions, of which that which is made by the moveable in it self,Finite and terminate circular motions disorder not the parts of the World. still retains it in the same place, and that which carrieth the moveable by the circumference of a circle about its fixed centre, neither puts it self, nor those about it in disorder; for that such a motion primarily is finite and terminate (though not yet finished and determined) but there is no point in the circumference,In the circular motion, every point in the circumference is the begining and end. that is not the first and last term in the circulation; and continuing it in the circumference assigned it, it leaveth all the rest, within and without that, free for the use of others, without ever impeding or disordering them. This being a motion that makes the moveable continually leave, and continually arrive at the end;Circular motion onely is uniform. it alone therefore can primarily be uniform; for that acceleration of motion is made in the moveable, when it goeth towards the term, to which it hath inclination; and the retardation happens by the repugnance that it hath to leave and part from the same term; and because in circular motion, the moveable continually leaves the natural term, and continually moveth towards the same, therefor, in it, the repugnance and inclination are always of equal force: from which equality results a velocity, neither retarded nor accelerated, i.e. an uniformity in motion. From this conformity, and from the being terminate,Circular motion may be continued perpetually. may follow the perpetual continuation by successively reiterating the circulations; which in an undeterminated line, and in a motion continually retarded or accelerated, cannot naturally be.Right motion cannot naturally be perpetual. I say, naturally; because the right motion which is retarded, is the violent, which cannot be perpetual; and the accelerate arriveth necessarily at the term, if one there be; and if there be none, it cannot be moved to it, because nature moves not whether it is impossible to attain. I conclude therefore, that the circular motion can onely naturally consist with natural bodies, parts of the universe, and constituted in an excellent disposure; and that the right, at the most that can be said for it, is assigned by nature to its bodies,Right motion assigned to natural bodies, to reduce them to perfect order, when removed from their places. and their parts, at such time as they shall be out of their proper places, constituted in a depraved disposition, and for that cause needing to be redurcd by the shortest way to their natural state. Hence, me thinks, it may rationally be concluded, that for maintenance of perfect order amongst the parts of the World, it is necessary to say, that moveables are moveable onely circularly; and if there be any that move not circularly,Rest onely, and circular motion are apt to conserve order. these of necessity are immoveable: there being nothing but rest and circular motion apt to the conservation of order. And I do not a little wonder with my self, that Aristotle, who held that the Terrestrial globe was placed in the centre of the World, and there remained immoveable, should not say, that
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