eX TrtAtife (/BODIES. 



But we mutt enlarge this proportion unto all motions, as we- 1 

 have done the former, of the encreafe it felf in velocity: becaufe 

 the reafbn of it is common to all motions. Which is, that all 

 motion ( as may appear out of what \ve have formerly faid ) 

 procecdeth from two caufes ; namely, the Agent or the force 

 that moveth, and the difpofition of the body moved, as it is 

 compofed of the three qualities we lately explicated. In which 

 is to be noted, that the Agent doth not move {imply by its 

 c\vn virtue, but it applyeth allb the virtue of the body moved> 

 which it hath to divide the medium when it is put on. As when 

 \ve cut with a knife, the effeft proceedeth from the knife prefled 

 on by the hand; or from the hand as applying and putting in 

 action the edge and cutting power of the knife. Now this in 

 Phyficks and Nature is clearly parallel to what in Geometry 

 and Arithmctick the Mathematicians call, drawing one num- 

 ber or one fide into another ; for as in Mathematicks, to draw 

 one number into another is to apply the number drawn unto 

 every part of the number into which it is drawn; as if we draw 

 three into feven we make twenty one, by making every unity 

 or part of the number feven to be three: and the like is of lines 

 in Geometry. So in the prefcnt cafe, to every part of the hands 

 motion, we addc the whole virtue of the cutting faculty which 

 is in the knife; and to every part of the motion of the knife, we - 

 ade!e the whole prcfiing virtue of the hand. Therefore the en- 

 creafe of the efTe proceeding from two caufes fo working, mull 

 allb be parallel to the encreafe of the quantities anting out of 

 the like drawing in Mathematicks. But inthofe, it is evident 

 that the encreafe is according to the order of the odde numbers, 

 and therefore it mull in our cafe be the like: that is, the encrcafe 

 muft be in the faid proportion of oddc numbers/ Now that in 

 thofe the CHcreafe proceedeth fo will be evident, if you confider 

 the encrcafe of an Equicrure triangle; w-hich becaufe it goeth up- 

 on a certain proportion of length and breadth, if you compare 

 the encreafes of the whole triangle (that gaincth on each fide) 

 with the encreafcs of the perpendicular (which gaineth onely in- 

 length) you will fee that they ftili proceed in the forefaid pro- 

 portion of odde numbers. 



Which will be better underftood, if we fet down the demon- 

 flrauon cfit: Ice the Equicrure triangle be A B G: and from the 



point. 



