Chap. 13. A Trcxtifi of BODIES. 



will prefently vanifh. Again, becaufe in the firft, the part at the 

 incidence is greater ; the flirface from which the reflexion is 

 made inwards, hath more of a plain and ftraight fuperficie? : 

 and confequently doth reflcA at a greater angle.then that,whofc 

 Hjperfictcs hath more of inclining. 



But wemuft not pafTe from thisqueftion, without looking a 10> 

 little into the nature of thofe bodies in which refraction is made: A confirmation 

 for if thcy,as well as the immediate caufes of refraction, do like- f ' h . e formcr , 



. r r MI i- t r d'.ftnnc, out of 



wile favour us; it will not a little advance the certainty tour de- the nature 

 termination. To this purpofe we may call to mind, how experi- 

 encefheweth us that great refractions are made in fmoke,and in 

 mifts, and in olifles, and in thick-bodied waters ; and Monfieur 

 Des Cartes addeth certain oyles, and fpirits or ftrong waters. 



Now moft of thefe we fee are compofed of little confiftent 

 bodies, fwirnming in another liquid body. As is plain in fiuoke 

 and miftsrfor the little bubbles which rife in the water before 

 they get out of it;and that are fmoke when they get into the aire; 

 do aflure us that fmoke is nothing elfe, but a company of little 

 round bodiesjfwimming in the aire : and the round confidence 

 of water upon herbs, leafs, and twigs in a rind or dew, gtveth 

 us allb to underftand that a mift is likewife a company ot little 

 round bodies that fometimes ftand, fometimes float in the aire, 

 as the wind driveth them. Our very eyes bear witnefTe to us, 

 that the thicker fort of waters are full of little bodies, which is 

 the caufe of their not being clear. 



As for glafle, the blowing of it convinceth, that the litrie 

 darts of fire which pierce it every way, do naturally in the melt- 

 ing of it convert it into little round hollow bodies, which in 

 their cooling muft fettle into parts of the like figure. Then for 

 cryftall and other tranfparent flones which are found in cold 

 places; it cannot be other wife, but that .the nature of cold pierc- 

 ing into the main body, and con-racling every little part in it 

 felf, this contraction muft needs leave vacant pores between 

 part and part. And that fuch tran'parcn: ftones as are made by 

 heat, have the like effeft and property^ rmy be judged out of 

 what we fee in bricks and tiles, which nrc lefc full ofholes by 

 the operation of the fire. And I have fccn in bones that have 

 lain a longtime in the fun, a multitude of fcnfible little pores 

 chofeto one another, as if they had been formerly ftuck all over 



with 



