Chap, 12. A Trtatifeof BODIES. n 



tion fo cafily as it doth rare bodies. This is the general! rcafon 

 for the conservation of motion in denfe bodies. But becaufc in 

 our cafe, there is a continuall caufc which conferveth motion in 

 the airc, the aire may continue its motion longer then'ofit felf it 

 would do : not in the fame part of airc which Gali!etis (as it 

 fcemcth) did aim at : but in divers parts, in which the moveablc 

 fucceffivcly is. 



Which being concluded, let us fee how the forced motion 

 comcth to decreafe and to be ended. To which purpofe we may 

 obfervc that the impreffion which the arrow receiveth fro:n the 

 aire that d i ivcch it forwards, being weaker then that which it 

 received ut the tirft from the ftring, f by reaibn, that the aire is not 

 fbdenfe.and therefore cannot ftrike fo great a blow)the arrow 

 doth not in this fecond meafure of time, (wherein we confider 

 the impulfe given by the aire onely) cut fo ftrongly the airc be- 

 fore it, nor prcflefb violently upon it, as in the firft meafure 

 when the ftring parting from it did beat it forwards:for till then 

 the velocity encreafeth in the arrow, as it doth in the firing that 

 carrieth it along, which procecdeth from reft at the fingers loofe 

 from it,to its higheft degree or velocity ; which is, when it arri- 

 veth totheutmoft extent of its jcrk,whereit quitteth the arrow. 

 And therefore the aire now doth Hot fo fwiftly, nor fomuch of 

 it, rebound back from before, and clap it felf behind the arrow, 

 to fill the fp:cc that elfe would be left void by the arrowes mo- 

 ving forward, and conicqucntly the blow it giveth in the third 

 mcature, to drive the arrow on, cannot be fo great as the blow 

 was immediately after the firings parting from it; which was in 

 the fecond meafure of time : and therefore the arrow muft needs 

 move flower in the thud meafure then it did in the fecond ; as 

 formerly it moved flower in the fecond (which was the aires 

 firft ftroke) then it did in the firft, when the ftring drove it for- 

 ward*. And thus fncceflivcly in every moment of time, as the 

 caufes grow weaker & weaker by theencreafeofrefiftance in the 

 aire before, and by the decreafe offeree in the fublequent airejfb 

 the morion muft be flower 5dflower,till it come to pure cefTation. 6 



As forGalileus fecond argumentjthat the aire hath little power t * n f an o fw d cr f 

 over heavy things ; and therefore he will not allow it to be the jeftion rhat the 



caufc of continuing forced motions in dcnle bodies : I wifh he aire hath no 



o i r P ewcr ovcr 



could as well have made experience what velocity or morion hea 



I a mans 



