%^ COLLECTION Oy MEMOIRS, 



augmentation of weight of metallic oxides might be attribute??; 

 exprefles himfeU as follows in his I6lh eflay : " (o this qu«f- 

 tion then, fupported on the grounds ah-eady mentioned, I an- 

 fwerand maintain with confidence, that the increafeof weight 

 arifes from the air of the veflel, which is condenfed, rendered 

 heavy, and adhefive, by the violent and long continued heat 

 of the furnace; this air mixes itfelf witli the calx (frequent 

 agitation conducing) and attaches itfelf to the minuteft mole- 

 cules, in the fame manner as wa-ter renders beavy fand which 

 is. agitated with it, and moifteus and adheres to the fmalleft 

 grains. 

 He oppofej other J' -^^y combats in this work the opinion of Cardan (lib. 5 

 curicatopinions, defubtilitate) on the augmentation of weight of metallic ox- 

 ides ; that of Scaliger, that of Ccefalpinus, who afcribed this 

 augraentalion to a foot condenfed and reffecled by the furnace, 

 which foot, according to their opinion, fell down upon the 

 metal. He fiiews likewife that the augmentation of weight 

 proceeds neither from the veflel, nor from any emanation of 

 the charcoal, nor from the humidity of the air. It is difficHit 

 to conceive how J. Rey could attain to thefe conclufions by the 

 force of reafoning alone, without experiment, and ignorant 

 as he was of many of the preliminary date. 

 His doftrlhes I' appears that towards the end of the laft century, wliea 



were not re«eiv. Boyle and fome of his cotemporaries created the new fcience 

 y °ye, of natural phifofophy, of which the ancients had not the 

 flighteft notion, the work, of J.. Rey was entirely forgotten.-— 

 Boyle, in his treatife on the weight of flame and of fire, pub- 

 Hftied in 1670, that is 4(7 years after the publication of Key's 

 work, makes no mention of it j proceeding upon forae illufory 

 experiments, he flill maintained at that time that the augmen- 

 tation of weight which the metals acquire by their oxidatioa 

 arifes from the fixation of fire. 

 — BorbyLe- Lemery, who was an exa6l and fcrupulous obferver, em- 



"i"y. braced the fame opioion :. he attributes the oxidation of metals 



and their augmentation in weight which accompanies that 

 operation, to the combination of igneous particles with the 

 metal. 

 Opinion of Charras, colem'porary of Lemery, afrribed that augmen- 



eharr^s, ialion to the acids of the wood and charcoal, which as he fup- 



pofed penetrated the vcflels and entered into couibination with 

 *- ■ - the metals. Since that lime the fame acid of wood and char- 



coal' 



