n $ 3rrttiift<f'&QT)lES. Chap. 12. 



{lone in its luuirall motion; do with their little -blows force ic 

 pcradventu re more violently & iwifcly then any impelling agent 

 we are acquainted with. can do. So that the impulfe which they 

 make upon the arrowy re fling violently upon it after fucha ve- 

 hement concuflion, and with a great velocity, muft needs caufe a 

 powerfull effe in that'which of "it felf is indifferent to any 

 motion any way. 



3. But unlefTe this motion of the aire do continue to beat Mill 



A further ex. upon the arrow, it will foon fall to the ground, for want of a 

 fcnncrdoarine caufe to drive it fprward;and becaufe the nacurall motion of the 

 aire ( being then the ouely one ) will determine it downwards. 

 Let us confider then how this violent rending of the aire by the 

 blow ' that the bow-ftringgiveth unto the arrow, muft needs 

 diibrdef the little atomes that fwim to and fro in it^and thatfbe- 

 inp heavier then the airejare continually defcendingdownwards 

 This di (order maketh fome of the heavier parts of them, get a- 

 bove others that a re lighter then they; which they not abiding, 

 do preiTe upon thofe that arc next them, and they up*on their 

 fellows: fo that there is a great commotion and undulation cau- 

 fed in the whole marie of aire round about the arrow : which 

 muft continue fomc time before it can be fatled;and it being de- 

 termined by the motion of the arrow that vray that it flideth, 

 it followeth that all this commotion and undulation of the aire, 

 ferveth to continue the arrow in its flight. And thus fafter then 

 any part behind can be icttled, new ones before are ftirred, till 

 the reiiftance of the medium do grow ftronger then the impulfe 

 of the movers. 



. Befides this.the arrow prc/Ting upon the aire before it, with a 

 greater velocity then the aire (which is a liquid rare body ) can 

 admit, to move all of a piece without breaking: it muft of ncccA 

 fity happen that the parts of the aire immediately before the ar- 

 row be driven upon others further off, before thcfe can be mo- 

 ved to gire place unto them ; fo that in fomc places the aire be- 

 cometh condemned, and confequently in others rarificd. Which 

 alib the wind that we make in walking (which will jfhake a 

 paper pinned loofely at the wall of a chamber towards which 

 we walk) and the cooling airecaufcd by fanning when we are 

 hot do evidently confirm. So that it cannot be doubted, but that 

 condensation and rarefaction of the aire muft aecefTarily follow 



the 



