BO DIES. Chap, ,13. 



4 



different to both the fur faces :k followeth>tliat ic iraporteth not 

 whether fuperficics you take to know the quality of reflexion 

 by. This principle then being fettled, that the reflexion muft fol- 

 low the nature cf the tangen: Uivfaces, and it being prov2d, that 

 in plain furfoccs it will happen ia fuch fort as we have explica- 

 te*.!, it follovseth that in any crooked fuperficies of what figure 

 foever the fame alio will happen. 



Now feeing we have formerly declared, that refractions are 

 but a certain kind of reflexions- what we have faid here of re- 

 flexions may be applyed to refractions. 



o. But there remaineth yet untouched one affection more of re- 



AWy ofuvca- fractions; which is that Come diaphanous bodies do in their in- 

 Ireater'por'es ward parts reflect more then others,(which is that which wecall 

 makethagiea refraction )as experience fhcweth us:concernine which effect, we 



terrefrattion rjtj-L LJ- i / 



then one oficf are to coniider that diaphanous bodies may in their composition 

 fer parts and j^yg two differences :for fbrne arecompofed of greater parts and 



leffer pores. . r i /r j i rr T 



greater pores others, or lefler parts and lefler pores. It is true 

 there may be other combinations of pores and parts, yet by thcfe 

 two the reft may beefleerned. As for the firft combination, we 

 fee that becaufe the pores are greater , a greater multitude of 

 parts of light may pa fie together through one pore; and becaufe 

 the parrs are greater, likewife a greater multitude of rayes may 

 reflect from the fame part, and may find the fame paffage quite 

 throughout the diaphanous body. On the contrary fide in the 

 fecond combination where both the pores and the parts of the 

 diaphanous body are little, the light rauft be but little that find- 

 eth the fame p adage. 



Now that refradion is greater or leffcr happeneth two wayes: 

 for it is either when one diaphanous body reflectech light at 

 more angles then another, and by conleqncnce in a greater ex- 

 tent of the fuperficies; or elfe when one body rcfledteth light 

 from the fame point of incidence in a /horter line & in a greater 

 angle then another doth. In both thefe wayjr? it is apparent 

 that a body coitipofed of greater partJ and greater pores,cxcecd- 

 rih bodies of the oppofite kind: for by renfon that in the firft 

 kind more light may beat againflone air;i bc*V in \\hich that 

 happened!, will make an appearance ft^-n a further parr of its 

 fuperficies: whereas in a body of tlic other &rt , the light that 

 beateth againft one of the little parts of ic will be fo liule as it 



will 



