Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/51

Book I. Earth; but at equal ditances, it is the ame everywhere; because (taking away, or allowing for, the reitance of the air), it equally accelerates all falling bodies, whether heavy or light, great or mall.

Thus the Weight is greater in a greater body, les in a les body; it is greater near to the Earth, and les at remoter ditances. This ort of quantity is the centripetency, or propenion of the whole body towards the centre, or as I may ay, its Weight; and it is ever known by the quantity of a force equal and contrary to it, that is just ufficient to hinder the decent of the body.

Thee quantities of Forces, we may for brevity's ake, call by the names of Motive, Accelerative, and Abolute forces; and for distinction ake consider them, with repect to the Bodies that tend to the centre; to the Places of thoe bodies; and to the Centre of force towards which they tend: that is to ay, I refer the Motive force to the Body, as an endeavour and propenity of the whole towards a centre, ariing from the propenities of the everal parts taken together; the Accelerative force to the Place of the body, as a certain power or energy diffused from the centre to all places around to move the bodies that are in them; and the Absolute force to the Centre, as endued with ome caue, without which thoe motive forces would not be propagated through the paces round about; whether that caue is ome central body, (uch as is the Load-tone, in Rh