112

Sir I»aac Newton’s Book I,

move with equal swiftness, and descend from that highestpoint through the line H B altogether like to the line A H inwhich it ascended; abating only the resistance of the air,which is not here considered. If the line HI be drawn fromthe highest point H parallel to the horizon, AI will be equalto i of BG in fig. 70, when the body is projected in the direc-tion A G, and equal to % of B H, when the body is thrown inthe direction A H, provided A D be drawn horizontally.

93. Thus I have recounted the principal discoveries,which had been made concerning the motion of bodies bySir Isaac Newton’s predecessors; all these discoveries, bybeing found to agree with experience, contributing to esta-blish the laws of motion, from whence they were deduced.I shall therefore here finish what I had to say upon thoselaws; and conclude this chapter with a few words concern-ing the distinction which ought to be made between absoluteand relative motion. For some have thought fit to confoundthem together; because they observe the laws os motion totake place here on the earth, which is in motion, after the famemanner as if it were at rest. But Sir Isaac Newton hasbeen careful to distinguish between the relative and absoluteconsideration both of motion and time 3 . The astronomersanciently found it necessary to make this distinction in time.Time considered in it self passes on equably without relation toany thing external, being the proper measure of the continu-ance and duration of all things. But it is most frequently con-ceived of by us under a relative view to some succession in

* Prin. Philof- pag. 7, &c.

sensible