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the author, so minute in his details, would have omittedsuch a circumstance; and besides, repeated experience hasconvinced me, that when gold, from any admixture, hascontracted a vitreous coat, and any small grains of it stickabout the crucible by means of this coat, the grains can-not by these methods be completely collected. 3. That thegold employed was fine, and that its specific gravity wasnineteen, was only supposed. The author himself appearsto have suspected its purity, for he fays that to removescruples on this head he caused a dram and a half of it,which had been purposely reserved, to be melted in hisassistant’s presence, and found it sine and well-coloured ;but surely the colour of the mass cannot be admitted as asufficient criterion of its purity. Indeed it could nothave been entirely pure; because, though it had been soat first, yet the process os parting, however carefully per-formed, would have left some silver in it. 4. Admit-ting the gold to have been perfectly fine, and no errorto have happened ; it will not follow that the gold wasdegraded or altered in its nature, or that the experimentgives any countenance'to the pretensions of the alchemists.Gold is strongly affected, in many of its properties, bythe admixture of very small proportions of certain otherbodies : a quantity of tin, less even than that which the■foregoing powder is supposed to have amounted to, rendersgold brittle. It is plain that at least sifty-three parts insixty of the gold in the above experiment were in likemanner debased only by the coalition of another matterwi-lh it, and that this extraneous matter was separable by-simple cupellation with lead. The history affords no rea-son to believe that the remainder of the gold might not:also have been recovered, by suitable management, fromthe ponderous fi-xt recrement: for gold has frequentlyhbeen -found debased and disguised by substances which

^resisted