CHAP. III. 

 Of Raritirand Denjitie. 



I Intend in this Chapter to look as farrc as I can into the na- 

 tureand caufcs ofthe twofirft differences 'of bodies which 

 follow out of Qiiamitic as it concurred! with fubftanceto Q 

 make a body : for, the difcovery of thetrij and of the various 

 proportions of them among themfclves, will be a great and 

 important ftep in the journey we are going. But thelcircitie of 

 our language is fitch, in fubjc&s removed from ordinary conver- 

 fation (though in others., I thin k none is more copious orcx- 

 prefTivc } as afFordeth us not apt words of our own to expreflc 

 Significantly fuch notions as I muft bufie my felf about in this 

 difcourfe. Therefore I will prcfume to borrow them from the 

 Latine fchool, where there is much ado about them. I would 

 expreffe the difference between bodies , that under the fame 

 mcafurcs and outward bulk, have a greater thinnefle and 

 cxpanfion, or thicknefle and foliditie, one then another ; 

 which terms, (or any I can find in English) do not fig- 

 nific fully thofe affeftions of Quamitic that I intend hereto 

 declare : therefore I will do it under the names of Raritieancl 

 Denfitiej the true meaning of which will appear by what we 

 fhall hereafter fay. 



It is evident unto us, that there are different forts of bodies, 2 . 



of which though you take equall quantities in one regard, yet it is evi^t 

 they will be unequall in another. Their magnitude* may be ifeVanTrarc"' 

 the fame, but their weights will be different or contrariwife, ^J Q &"* 

 their weights being cquall, their outward meaiures will not be obfcare^h^ 

 fo. Take a pintc of aire; and weigh it againft a pinte ofwa- the / are fuc ^ 

 ter, and you will lee the ballance of the laft go down amain* 

 but ifyou drive out the airc by filling the pinte with lead, 

 the other pintc in which the water is, will rife again as faft : 

 which ifyou poure out, and fill that pinte with quickfilver, 

 you willperccire the lead to be much lighter : and ngain> you. 

 will find a pinte of gofd heavier then fb much Mercuric. And in 

 like manner, ifyou take a way- of the lieavje bodies till they a- 

 grec in weight with thelighter,they will take up & fill different 

 proportions^and parts ofthe mcafure that fhall contain them. 



But from whence this effect arifeth, is the difficultie that we 



B 2 would 



