Sometimes they have a solution of silver in nitric acid, or of gold in aqua regia, or an amalgam of gold or silver, which being adroitly introduced, furnishes the requisite quantity of metal. A common exhibition was to dip nails into a liquid, and take them out half converted into gold. The nails consisted of one-half gold, neatly soldered to the iron, and covered with something to conceal the colour, which the liquid removed. Sometimes they had metals one-half gold the other half silver, soldered together, and the gold side whitened with mercury; the gold half was dipped into the transmuting liquid and then the metal heated; the mercury was dissipated, and the gold half of the metal appeared.[22] [22] Mem. Paris, 1722, p. 61. As the alchymists were assiduous workmen--as they mixed all the metals, salts, &c. 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 discovery of new substances, possessed of much greater activity than any with which they were previously acquainted. In this way they were led to the discovery of sulphuric, nitric, and muriatic acids. These, when known, were made to act upon the metals; solutions of the metals were obtained, and this gradually led to the knowledge of various metalline salts and preparations, which were introduced with considerable advantage into medicine. Thus the alchymists, by their absurd pursuits, gradually formed a collection of facts, which led ultimately to the establishment of scientific chemistry. On this account it will be proper to notice, in this place, such of them as appeared in Europe during the darker ages, and acquired the highest reputation either on account of their skill as physicians, or their celebrity as chemists.[23] [23] The original author, whom all who have given any account of the alchymists have followed, is Olaus Borrichius, in his Conspectus Scriptorum Chemicorum Celebriorum. He does not inform us from what sources his information was derived. 1. The first alchymist who deserves notice is Albertus Magnus, or Albert Groot, a German, who was born, it is supposed, in the year 1193, at Bollstaedt, and died in the year 1282.[24] When very young he is said to have been so remarkable for his dulness, that he became the jest of his acquaintances. He studied the sciences at Padua, and afterwards taught at Cologne, and finally in Paris. He travelled through all Germany as Provincial of the order of Dominican Monks, visited Rome, and was made bishop of Ratisbon: but his passion for science induced him to give up his bishopric, and return to a cloister at Cologne, where he continued till his death. [24] Sprengel’s History of Medicine, iv. 368.