Chap. 8. 4 Trtdtije of B O D I E S. 75- 



i. to 125000; and that the den/ity of the light we have here in 

 the earth, is to the denfity of that part of fire which is in the 

 funncs body, as the body of the funne isto^that body which is 

 called Orbis tnagnus ( whole femidiamccer is the diftance be- 

 tween the funne and the earth;) which muft be in fubtriple 

 proportion of the diameter of the funne to the diameter of the 

 great orb: it fblloweth that 125000. being mulciplyed by the 

 proportion of the great orb unto the funne (which Galileo tcl- 

 Icth us is as 106000000. unto one) will give a fcantling of what 

 degree of celerity light muft have more then acorn of gunpow- 

 der, to rccompencc the excefle of weight which is in a corn of 

 gunpowder.above that which is in a ray of light,as big as a corn 

 ofgunpowdcr. Which will amount to be much greater then the 

 proportion of the femidianietcr cfiOrbismAgnttsxo the femidia- 

 meter of the corn of gunpowder: for if you reckon five grains of 

 gunpowder to a barly-corns breadth.and 1 2.of them in an inch, 

 and 12. inches in a foot, and 3. feet in a pace, and 1000. paces 

 in a mile, and 5500. miles in the femiJiameter of the earth, and 

 ' 1208' femidiameters of the earth in the femidiameter of the Or- 

 kit magnns, there will be in it but 9152480000000. grains of 

 gunpowder ; whereas the other calculation maketh light to be 

 i 3250000000000. times rarer then gunpowder; which is almort 

 ten times a greater proportion then the other. And yet this cele- 

 rity fupplyeth but one of the two conditions wanting in light 

 to make its perctiffions fenfible, namely denficy. Now becaufe 

 the lame velocity in a body f a lefler bulk, doth not make fb 

 great a pcrcufs-ion as it doth inabigger body;and that the little- 

 nefle ofthe leaft parts of bodies followeth the proportion oftheir 

 rarity; this vaft proportion of celerity muft again be drawn in- 

 to it fclf, to fupply for the excefle in bignefle that a corn of gun- 

 powder hath over an atome of light: and the product of this 

 multiplication will be the celerity required to fupply for both 

 defects. Which evidently fheweth, it is impofsible that a ray of 

 light fhould make any fenfiblc percufsion, though it be a body. 

 Especially confidering that fenfe never takech notice of what is 

 perpetually done in a moderate degree. And therefore after this 

 minute looking into all eircirnHances, we need not have diffi- 

 culty in allowing unto light the greateft celerity imaginab'c.and 

 a pcreufsion proportionate to fuch a celerity in fo rare a body; 



and 



