Tfwisiationo/Rey'a Essays. 265 



philosophy, that the elements, by mutual conversion from one 

 into another, lose or gain weight, in proportion as they are 

 rarefied or condensed, in the change. Armed with this reason, 

 I boldly enter the lists, to combat the error ; and I maintain' 

 that gravity is so united to the first matter of the elements, that 

 . It cannot be deprived of it. The weight that each portion re- 

 ceives m Its cradle, it carries to its coffin. In whatever place 

 under whatever form, to whatever volume it be reduced, always 

 one same weight. But not presuming that my assertions will 

 rank with those of Pythagoras, and that it will be sufficient to 

 have advanced them, I support them by a proof in A^hich I 

 thmk all liberal minds will acquiesce. Take a portion of 

 earth possessing the least possible weight that can be con- 

 ceived ; let this earth be converted into water, by the means 

 known and practised by nature, it is evident that this water 

 will have weight, because all water must have it: now it will 

 be greater or less, or equal to that in the earth. Greater, they 

 will not say it is, (for they profess the contrary,) and I also deny 

 It; less It cannot be, seeing that we have taken the least possible 

 quantity : ,t remains therefore that it must be equal to it, which 

 IS what I intended to prove. What is demonstrated of this 

 portion IS demonstrable of two, three, or any, however great 

 number, in short of the whole element, which is composed of 

 nothing else, and is equally referable to the conversion of water 

 mto air, and air into fire, and vice versd of these last into the 

 others. 



Essay VII. 

 How to ascertain to what volume of air, a certain quantity, of 

 water is reduced. 

 Philosophers have often talked of the extension which a solid 

 element acquires, by conversion into one more rare, and have 

 attempted to assign its proportion : but I do not remember to 

 have read any thing supported by sound reasoning or experi- 

 raent. Now since in the preceding essay, I have spoken of 

 this enlargement, the knowledge of which opens the door to 

 many beautiful and admirable devices, I will not deprive the 

 curious reader of a means, which I have thought of, to make 



