P R E F A C E.

original: "essem..." This text picks up mid-sentence from the previous page, where Newton was discussing the application of his principles to the system of the world. ...[once I] had [done this], I then also began to try other things which relate to the laws and measures of gravity gravity: from the Latin "gravitas," meaning heaviness; Newton is here establishing it as a measurable mathematical force and of other forces vires: the physical powers that act upon objects to change their motion, and to the shapes to be described by bodies attracted according to any given laws; also to the motions of several bodies among themselves, to the motions of bodies in resisting mediums Newton is referring to how objects move through fluids like air or water, which offer resistance., to the forces, densities, and motions of those mediums, to the orbits of comets and similar matters. I thought that publication should be postponed to another time, so that I might investigate these other things and release them to the public together. Those things which relate to lunar motions (since they are imperfect) I have gathered together in the corollaries of proposition 66, lest I should present each one by a method more long-winded than the dignity of the subject requires, or be bound to demonstrate them individually and thus interrupt the sequence of the remaining propositions. I preferred to insert some things discovered late in less suitable places rather than change the numbering of the propositions and the citations. I earnestly request that everything be read with an open mind, and that defects in such a difficult subject be not so much criticized as investigated by the new efforts of my readers and kindly corrected.