Chap. 8. 4 Tr<4tift*f BODIES. $ 9 



arc forced to let it cool by degrees in fuch relenting* of fire, as 

 they call their nealing heats, left itfliould fliiverin pieces by a 

 violent fucceeding of airc in the room of the fire; for that being 

 of gre-ater parts then the fire, would ftrain the pores of the 

 ghfle too fuddcnly, and break it all in pieces to get ingrefsion: 

 whereas in thole nealing heats the aire being rarer, lefler parts 

 of itfuccecdto the fire > andlcifurcly ftrccch the pores without 

 hurt. And therefore we need not wonder that light pafleth fo 

 eafily through glaflc; and much lefle, that it gctteth through 

 other bodies ; feeing the experience of Alchymifts doth a- 

 fure us , that ic is hard to find any other body fb impenetrable 

 as glafle. 



But now to come to the anfvver of the firft, and in appea- 

 rance moft powerful), objeftion againft the corporeity flight; That light doth 

 which urgeth that his motion is performed inaninftant, and not cnli fi h . rc 



it it i i -i a "vroaminaa 



therefore cannot belong to what is matenall and clothed with inftantjamichat 

 quantity. We will endeavour to fhew how unable thcfenfe is *^f^_ 

 to judge of fundry forts of motions of Bodies, and how greffe- n doth make 

 ly it is miftakcn in them. And then, when it fhall appear that 

 the motion of light muft neceflarily be harder to be obfer- 

 ved then thofe others: I conceive , all that is raifed againft 

 our opinion by fo incompetent a judge, will fall flat to the 

 ground. 



Firft then, let me put the Reader in mind , how if ever he 

 marked children when they play with fire-flicks , they 

 move and whirle them round fo faft , that the motion will 

 cofen their eyes , and reprcient an entire circle of fire un- 

 to them : and were it fomewhat diftant > in a dark night, 

 that one played fo with a lighted torch , it would ap- 

 pear a conftant wheel of fire without any difcerning of 

 motion in it. And then, let him confidcr how flow a 

 motion that is in refpc& of what it is pofslble a body may 

 participate of : and he may fafely conclude , that it is no 

 wonder though the motion of light be not dcfcried, and that 

 indeed no argument can be made from thence , to prove that 

 light is not a body. 



But let us examine this confideration a little further , and 

 compare it to the motion of the earth or heavens : let the ap- 

 pearing circle of the fire, be fbme three foot diameter, and the 



E time 



