Chap. i. PHILOSOPHY. 41

it would really have been, had the body been truly at relbwhen die power was applied. From hence it follows, thatwhen the eye is advanced to K, the body will appear fome-where in the line K H L. Suppofe it appear in M ; then it ismanifeft, from what has been premifed at the beginning ofthis paragraph, that the diftance H M is equal to what thebody would have*run upon the line E G, during the time,wherein the eye has palled from F to K, provided that the bo-dy had been at reft, when ailed upon in E. If it be fartherasked, after what manner the body has moved from E to M ?I anfwer, through a ftraight line ; for it has been Ihewn abovein the explication of the lirft law of motion, that a mov-ing body, from the time it is left to it felf, will proceed on inone continued ftraight line.

xi. If E N be taken equal to H M and N M be drawn ;(ince H M is equidiftant from EN, N M will be equidiftantfrom E H. Therefore the effect of any power upon a movingbody, when that power aits obliquely to the motion of thebody, is to be determined in this manner. Suppole the bo-dy is moving along the ftraight line A E B, if when the body iscome to E, a power gives it an impulfe in the direilion of theline EG, to find what courfe the body will afterwards takewe muft proceed thus. Take in EB any length EH, and inE G take fuch a length E N, that if the body had been at reftha E, the power applied to it would have caufed it to moveover E N in the fame fpaceof time, as it would have employedin palling over EH, if the power had not ailed at all upon it.Then draw HL equidiftant from EG, and N M equidiftant

G from