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ness it produced, to be true silver. He says, that evenwith good aqua regis, he could obtain from the very best;gold some little quantity of such a white powder, but inso very small proportion, that he never had enough atonce to make him think it worth while to prosecute suchtrials.

It were to be wished that the ingenuous author had beenmore careful in ascertaining the purity of the gold madeuse of in these experiments, and noted the exact quantityof silver obtained from it. Gold parted from silver orcopper by aqua fortis, is by no means to be looked uponas being pure : nor is there perhaps any other method, asyet known, of perfectly purifying it from silver, thanthat by which the silver was separated in the above expe-riments ; the dissolution in aqua regia being in effect noother than a purification of the gold. Even aqua regia,when made with an under proportion of marine acid,will not produce a complete separation; this imperfectaqua regia taking up, along with the gold, a little silver,separable by a second dissolution.

Mr. Boyle has given an account also of a very extraor-dinary experiment, under the title of the degradation ofgold by an anti-elixir, which was published in his ownlife time, and since reprinted in 1739. The known cha-racter of the author, the earnest desire he has shewn inall his writings for the discovery of truth and the exposingof false pretences, have not only rendered the fact un-questionable, but likewise induced many to adopt theconsequences which he thought might be drawn from it;and to regard it as a proof of the real alterability of gold,and as strongly favouring the alchemical doctrine of thetransmutability of metals. I shall therefore insert the ac-count of the experiment in the author’s words, and sub-join a few remarks; lamenting that it is not in my power5 to