THE ESSAYS OF JEAN REY. 253 



stones and plants increase in weight when they are calcined ? I 

 add, finally, that air which is forced into a globe full of it, com- 

 ing out diminishes the weight of the vessel instead of increasing 

 it, as Scaliger believes." He rejected the comparison of the lead 

 with the tile, saying, " The tile increases in weight by the shrink- 

 ing of its extent ; the lead by the matter that is added to it." 



Csesalpin had supposed, as Libarius records, in explanation 

 of the phenomenon, that the soot produced by the fire struck the 

 roof of the furnace and fell back upon the matter. Rey answered 

 that the soot would blacken the lead instead of communicating a 

 white tint to it. Moreover, if this were the cause, the production 

 of earth might be carried on indefinitely by keeping up the fire, 

 which was not the case. Libarius said that even apprentices in 

 chemistry would laugh at Csesalpin's theory. 



Rey also showed that the increase in weight could not come 

 from the iron vessel in which the calcination took place, for the 

 earth would not continue white in contact with the dust of iron ; 

 besides, the vessel would be consumed in two or three operations, 

 instead of being serviceable every day for several years; and, 

 finally, if it was so, we should obtain from a very small quantity 

 of tin or lead a very large quantity of earth, which is contrary to 

 the experiment. Furthermore, a German chemist, Modestinus 

 Fachsius, who also occupied himself with the question, concluded 

 from the examination of the metals, the cupel, the lead, and the 

 metal under trial, that all are heavier after the calcination than 

 before they were exposed to the fire. 



Deschamps assumed that the increase of weight was due to 

 vapors of charcoal traversing the vessel. Rey answered that such 

 vapors could not traverse a globe of glass, a plate of tin, or an 

 earthen pot, because boiling water, sauces, and potages were not 

 infected by them. How, then, could they traverse an iron vessel ? 

 Even if they did, why should they stop in the earth instead of 

 going on? 



Deschamps did not stop with this, but insisted that charcoal had 

 two parts or natures, a vegetable and a metallic nature, and that 

 each of them had two others, one fixed and the other volatile. 

 The fixed part remains in the ashes, from which a fixed salt can be 

 obtained by washing ; but the volatile part, being of a mercurial 

 nature, ascends around the vessel ; and he made the objection to 

 Rey's proposition that " the volatile part, lifted up on the wings 

 of moisture, meeting the air which is directly on the vessel, being 

 more rarefied and less heavy than the vapor that issues from the 

 coal, is taken up by that in the vessel, and attaches itself by a 

 close sympathy to the fixed salt of the earth of tin, which, having 

 taken a certain quantity of it, and being, as it were, satiated, rejects 

 the surplus." This observation, purely theoretical and made by 



