78 Translation of Key's Essays 



from Father Mersene to the physician, John Rey, in which he 

 attacks the natural philosophy of that author,— the second, 

 Key's answer to Mersene, in which he defends himself with all 

 his might. 



Title. 



Essays hi/ Jo ai'i Rey, Doctor of Physic, on an Inqiiiryinio the 



Cause why Tin and Lead Increase in Weight by Calcination. 



A Bazas. 

 Par Guillaume Melanges, Iniprimeur ordinaire dii Roy, 

 1630. The Essays are dedicated to Monseignenr the Prince of 

 Sedan, and the dedication itself is curious and diverting, hut 

 too long to be inserted. 



M. Brun's Letter, which gave rise to the present Essays. 



To M. Rey. 



Sir, — Wishing a few days since, to calcine some tin, I 

 weighed out two pounds six ounces of the finest sort, from 

 England, put it into an iron vessel fitted to an open furnace, 

 and keeping it continually stirred over a strong fire, without 

 adding any thing, I converted it in six hours, into a very white 

 calx. I weighed it to ascertain the loss, and found there were 

 two pounds thirteen ounces of it. This occasioned me incre- 

 dible astonishment, not being able to imagine, from whence the 

 seven ounces of increase could be derived. I made the 

 same trial with lead, of which I calcined six pounds, but 

 in this I found a loss of six ounces. I have inquired the cause 

 of many learned men, particularly of Dr. N. * but no one has 

 been able to declare it. Your ingenuity which, when it pleases, 

 soars beyond the common flight, will here find matter of 

 occupation, and I beseech you most earnestly to inquire into 

 the cause of so rare an effect, and so far to oblige me that, by 

 your means, I may be enlightened in regard to this miracle. 



* Deschaiiip.i. All ihe notes witli a numeral referejice, are from llic 

 reprint by Gobet. 



