A Letter from Mr. Emanuel Mendes da Costa, Librarian, &c. to the Royal Society, to M. Maty, M. D. Sec. R. S. Containig a Supplement to the Account of the Discovery of Native Tin, Art. VII

XXXIX. A Letter from Mr. Emanuel Mendes da Costa, Librarian, &c. to the Royal Society, to M. Maty, M. D. Sec. R. S. containing a Supplement to the Account of the Discovery of Native Tin, Art. VII. Dear Sir, I Communicate to you the following paragraph from a letter written to me by the Rev. William Borlase, LL. D. and F. R. S. of Ludgvan, near Penzance, in Cornwall, and bearing date November 23 last past. As it is a paragraph relative to the native tin found in Cornwall, which I had the honour to communicate to the Royal Society on the 6th of March last, and is ordered to be printed; permit me to beg of you to read it at the meeting to-morrow, that, if judged worthy by the Committee of papers, it may be printed with the former paper as a part of it. I am, with great respect, SIR, your very obliged humble servant, Royal Society house, December 17, 1766. Emanuel Mendes da Costa. Vol. LVI. EXTRACT. "Mr. Henry Rosewarne, of Truro, says, that when he sent the first specimen (presented to the Royal Society by me William Borlase, and now lodged in their Museum) he mentioned as a proof of its being native tin, that between the ore and the tin there was a mixture of quartz: but, upon a nearer examination and some trials with aqua fortis, he and another person found it was not quartz. At last, on melting a piece, he perceived no small quantity of arsenic to be mixed with it, and therefore suspected that the white parts which had passed for quartz were nothing but arsenic. Accordingly he scraped off a little of it and put it on a red hot iron, where it immediately caught fire, and evaporated into smoke, leaving behind it the most poisonous stench they ever smelt. This confirmed some, who had hitherto doubted, in the most firm belief that it really was native tin and genuine, it being impossible for tin to be melted and the arsenic left untouched."