3 'jfTrtttifi */ BO DIES. Chap. 13* 



Antnfwer -o them : for when a canon bullet iliot into a rirer, hurtwh the 



llroi'v TrTfi" people on ^ C ot ' icr ^ e ; " is not cau ^ ty refraction, but by 

 ,ourofMonfi- rcflc&ion, as Monficur DCS Cartes himfelf acknowledgech:and 

 fcs r U$ C opinion. therefore, hath no force to prove any thing in refraftion; whole 

 laws are divers from thofe of pure reflexion. 



And the fame anlwcr fcrveth againft the inftance of a musket 

 b"l!et foot at a mark under water ; which perpetually lighteth 

 higher then the mavk,thoi!gh it be exaflly juft aimed at.For we 

 knowing that it is the nature of water ,by fiftking in one place to 

 rift round aboivt,k muft of necefficy follow that the bullet which 

 Jr> entring hath preffed down the firft parts of the water* hath 

 wkhaH thereby put others further off in a motion of rifing: and 

 therefore the bullet in its gorng on rmifii meet with fbme water 

 fweHing tjpwak,4c mwft from it receive a ply that way,which 

 canoot fail ofearrying k above the mafk it was levelled at. And 

 fo we fee this cffeft proceedeth from reflexion or the botmding 

 of the warcr, and not from refraction. Befidejtha-c, it may juft- 

 ly be fufpefted the fhoorer took his aim too high, by rcafbn of 

 the marks appearing in the water higher then in truth it isrun- 

 leife iWh falle aitriing were duly prevented. 



Nekner is Monfieur Des Cartes his ex<rufe to be admitted, 

 when he fakh that light goech otherwffe then a ball would do, 

 becaufe chat in a glaiTe or in water,the etheriall fuWTance which 

 he fuppofcth to run through all bodies,is more efficacioufry mo- 

 ved then in aire: and that therefore light mutt go fairer in the 

 glafle then in the aire, and fo turn on that fide of the ffraighc 

 line which is contrary ro the fide that the ball takethj becaufe 

 rfve ball gocth not fo fwifrly. For ( not to difpute of the verhy 

 of this propofition) the efFecl: he pretendeth is impo/Tible : for rf 

 the etheriall lubftance in the aire before the glaflcbc ffowly mo- 

 red, (the motion of which he calleth light } it is impofTiblc that 

 the ttheriall lljbltance in theglafle or in the water fhouW &c 

 more fmartly moved then it. Well it may be Jefle; but without 

 all doubt the impulfc ofthc etheriall fubttance in thtgfaflc can- 

 not be greater then its adequate caufc, which is the motion ofthe 

 other parts that are in the aire precedent toglafic. 



Again, after it is paflkd theglafle, ir ftioidd return to be a 

 ftraightlinc with the line that it made in the aire precedent to 

 the glaffe: leeing that the fubfeauent aire rmift take off juft as 

 much (and no more)as theglafle did adder the contrary wrrere-- 



