280 Translation of Key's Essays. 



in his calcination, so great a quantity should have proceeded. 

 For we must not only suppose seven ounces, but also that which 

 has replaced the diminution of weight derived from the loss of 

 vapours of tlie tin, and from its increased volume, and more- 

 over, all that the fumes of the charcoal have carried off else- 

 where, not only through the whole laboratory, but out of it, 

 whither they have escaped in abundance by the openings. In 

 which fumes, if there were salt in proportion to that which has 

 sunk into the vessel, from those fumes that were above it, and 

 it were all collected together, truly the collection would be 

 monstrous! 



And besides, when the calx of tin had taken its fill of salt, 

 by this imaginary sympathy, what prevents the continuation of 

 the fire from accumulating more above it, and filling the vessel, 

 since it descends into it by its own weight? Experience refutes 

 all this — besides that I have demonstrated, that the air above 

 the vessel is so thick, that it could not descend into it. More- 

 over, if a furnace be constructed in a wall separating two 

 chambers, so that the vessel may be on one side, and the 

 registers and doors for putting in the charcoal and admitting 

 air on the other, I maintain that the increase of weight will 

 ensue, though no vapours can enter the chamber containing the 

 vessel. This I have confirmed by proof, which I made in the 

 forges of my elder brother, John Rey, Sieur de la Perotasse ; 

 when I found an equal increase in tin that I calcined, on what 

 they call a gtteuse, or ingot of iron, weighing from sixteen to 

 twenty quintals, at the instant that flowing from the furnace it 

 is thrown into its mould. Now it cannot be said, that the va- 

 pours of the charcoal contribute any thing in this case. Where- 

 fore this volatile salt is inadmissible in this matter. 



ESSAY XXIII. 



Volatile mercurial salt is not the cause of the increase. 



Some days after the refutation I have just mentioned, the 

 same person sent me another of his opinions ; namely, that the 

 volatile salt is of a mercurial nature, not containing any one of 

 the three principles absolutely pure, but mixed with the others, in 



