ALCHEMY was originally the pretended art of making gold and silver; but another and subsequent object of alchemy was the pre paration of a universal medicine. Those alchemists who were supposed to be skilled in the art were termed adepts or the adepts.
According to the doctrine of the alchemists all the metals are compounds, the baser of them containing the same constituents as gold, but mixed with various impurities, which being removed, the common metals would assume the properties of gold. The change was to he effected by lapis philosophoruni, or the philosophers' stone, which is commonly mentioned as a red powder poisessing a pecu liar smell.
As the philosophers' stone was said to take a great part in the pretended transmutations, Dr. Thomson in his ' History of Chemistry,' has endeavoured to discover its probable character. After quoting a description given by one of the alchemists, he states that this mysterious agent could hardly have been any thing else than an amalgam of gold; and there is no doubt,' he adds, ' that amalgam of gold, if projected into melted lead or tin, and after wards cupellated, would leave a portion of gold; all the gold, of course, that existed pre viously in the amalgam. It might, therefore,
have been employed by impostors to persuade the ignorant that it was really the philoso phers' stone; but the alchemists, who pre pared the amalgam, could not be ignorant that it contained gold.' It is thought by some that the alchemists did injury to chemistry, by bringing it into disrepute; but Dr. Thomson remarks, that a compensation was given in another way: ' As the alchemists were assiduous workmen— as they mixed all the metals, salts, loc., with which they were acquainted, in various ways with each other, and subjected such mixtures to the action of heat in close vessels, their labours were occasionally repaid by the dis covery of new substances, possessed of much greater activity than any with which they were previously acquainted .....Thus the alche mists, by their absurd pursuits, gradually formed a collection of facts, which led ulti mately to the establishment of scientific che mistry.'