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known, and these but partially and imperfectly, deservedto be submitted to all the kinds of operations that arepractised on the other metals, and to all the agents bywhich other metals are found to be affected. In the be-ginning of the ) ear 1754, his excellency general Wall,,at that time ambassador from Spain, enabled me to pro-ceed in the experiments, by fending me about an hundred,ounces; and I was afterwards favoured with considerablequantities more by some other gentlemen; The mostingenious and experienced chemists in Europe, as soon asthey could obtain any of the new metal, entered into thesame pursuits; and several, of. these enquiries have fromtime to time been made publick.

The first publication I have seen on this subject is thatof Mr. Wood, in the 44th volume of the Philosophical.Transactions, for the years. 1749 and 1750.. To thehistorical observations, of which an abstract has been givenabove, Mr. Wood subjoins a few experiments, madepartly, as may be presumed from their event, on. thetrue platina in grains, and partly on the cast metal; oneof which experiments, the cupellation of the cast metalwith lead, was afterwards repeated, more circumspectly,by Dr. Erownrigg..

In the 48th volume of the Transactions, part nd, forthe year 17^4, is inserted an.account of the principalexperiments which, had been then made on the platinaby me. They are divided into four papers, which arefollowed in the next volume by two papers more.

On the publication of the first four,. I was informedthat Mr. Scheffer also had given an examination of thismetal in the Handlingar of the Swedish. academy ofsciences for the year 1752. Those books-being difficultlyprocurable in this country, and written in a languagewhich I did not understand,, it was some time before I

could