A -Treatifi ^/BODIES. Chap, 8. 



But if Gnlilcus his conception be well grounded ; that light- 

 ning giveth us an incling of its motion, beginning from a 

 little and encreafing ro a greater ; or if Monfieur des Cartes his 

 opinion that it goeth flower in rcfraCHon, be true: we fhall 

 not need to ftudy long for an anfvver. But in Galileus his ex- 

 perience, it may be the breaking of the cloud which receivedi 

 that fucceflion of motion which we fee : and no flownefTe that 

 light can acquire by the refiftancc of the refracting body-can be 

 fb great as to make that difference of lines wlrch Monfieur 

 DCS Cartes molt ingenioufly C though I much doubt not truly ) 

 hath applycd to yield the reafon of refraction : as will appear 

 in our further difcourfe. 



Therefore, thefe being uncertain ; we will, to fhew the un- 

 reafonablenefleofthisqueftion, fuppofe there may be fomcob- 

 fervable tardity in the motion of light ; and then ask of them, 

 how we fhould arrive to perceive it ? What fenlc fhould we 

 hr.ploy in this difcovery ? It is true, we are fatisfiedthat found 

 takcth up time in coming to our cares : but it is, becaufc our 

 eyes are nimbler then they, and can perceive a good way di- 

 ftant the carpenters ax falling upon the timber that he hewetb, 

 or the fire flafhing out of the canon, before they heare any 

 newesof them : but fhut your eyes ; or inquire of a blind 

 man ; and then neither you nor he can tell whither thofe 

 founds fill your cares at the very inftant they were begotten, 

 or have fpcnt fome timt in their journey to you. Thus then our 

 eyes inftruA our cares. But is there any fcnfe quicker then the 

 fight? or means to know fpeedier then by our eyes ? Or can 

 they fee light, or any thing elfe ; untillitbc with them? We 

 may chen afluredly conclude, that its motion is not to be diC- 

 cerned as it cometh upon us ; nor it fclf to be perceived, till its 

 beams are in our eyes. 



But if there were any means to discover its motion, furcly 

 it muft be in fome medium, through which it muft ftrugg le to 

 get, as fire doth through iron ; which increasing there by de- 

 grees, at laft ( when it is red hot ) fendeth beams of light quite 

 through the plate that at the firft refufcd them paflage. And it 

 maketh to thif purpoie, that the light-conferving ftoncs which 

 are gathered in Italy, muft be fet in the funne for fome while 

 before they retain light: and the light will appear in them 



when 



