140 Translation of Rey's Essays. 



says he, transmutation does alter it ? " Why does burning 

 increase the weight of lead?" Because, says he, burning does 

 increase it. Observe, I pray you, if what he says of Csesalpin's 

 reasons, be not applicable to his own ? Certainly one need not 

 be a great chemist, nor a great logician withal, to laugh at it- 

 He that likes may admit these reasons, for my part I never shall 

 adopt them. But I blush to disclose the disgrace of this per- 

 son, who otherwise deserves great praise for the number of 

 works he has published, full of much learning. 



ESSAY XX. 



The increased weight of the calx of tin, or lead, is not derived from 

 the vessel. 

 I now come to opinions which, as far as I know, have not 

 been committed to writing. As nothing is in contact with the 

 tin and lead during calcination, except the air and the vessel, 

 they who will not acknowledge the former as the cause of its 

 increased weight, cannot, I think, haverecourse, with any seem- 

 ing to aught but the latter. For they might persuade themselves 

 that, during the calcination and continual stirring of the afore- 

 said metals, the iron by burning becomes friable at its surface, 

 a portion of which might mix with the calx, and so increase its 

 weight; just as pearls, which the apothecary pounds in his 

 marble mortar, acquire weight by the addition of the stony 

 matter which, crumbling off, mixes with them, often to their 

 prejudice to whom they are afterwards disposed of. But to 

 do away this opinion, I observe, first, that if the powdered iron, 

 which is brown, were to mix in such large quantity with the 

 tin, it would render its calx dark coloured, which nevertheless 

 is always white. Secondly, if the vessel were thus consumed, in 

 two or three calcinations at most it would become useless ; 

 whereas, it lasts many years, though used every day. Thirdly, 

 from a very little tin or lead we should obtain abundance of 

 calx, the whole vessel being easily reduced to powder by con- 

 tinuing the fire, which experience contradicts. What is more, 

 Modestinus Fachsius has observed, (as Libavius relates in the 



