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Page:Popular Science Monthly Volume 44.djvu/263

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THE ESSAYS OF JEAN REY.

stones and plants increase in weight when they are calcined? I add, finally, that air which is forced into a globe full of it, coming 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 shrinking of its extent; the lead by the matter that is added to it."

Cæsalpin 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 Cæsalpin'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