Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/346

 them all. I here ue the word attraction in general for any endeavour, of what kind oever, made by bodies to approach to each other; whether that endeavour arie from the action of the bodies themelves as tending mutually to, or agitating each other by pirits emitted; or whether it aries from the action of the æther or of the air, or of any medium whatoever, whether corporeal or incorporeal, any how impelling bodies placed therein towards each other. In the ame general ene I ue the word impule, not defining in this treatie the pecies or phyical qualities of forces, but invetigating the quantities and mathematical proportions of them; as I obervtd before in the definitions. In mathematics we are to invetigate the quantities of forces with their proportions conequent upon any conditions uppoed; then when we enter upon phyics, we compare thoe proportions with the phænomena of Nature; that we may know what conditions of thoe forces anwer to the everal kinds of attractive bodies. And this preparation being made, we argue more afely concerning the phyical pecies, caues, and proportions of the forces. Let us ee then with what forces phærical bodies coniting of particles endued with attractive powers in the manner above poken of mut act mutually upon one another; and what kind of motions will follow from thence.