When an ardent and ambitious mind is once dazzled with the fascination of some lofty pursuit, where gold is the object, or fame the impulse, it is difficult to pause in a doubtful career, and to make a voluntary shipwreck of the reputation which has been staked. Hope still cheers the aspirant from failure to failure, till the loss of fortune and the decay of credit disturb the serenity of his mind, and hurry him on to the last resource of baffled ingenuity and disappointed ambition. The philosopher thus becomes an impostor; and by the pretended transmutation of the baser metals into gold, or the discovery of the philosopher's stone, he attempts to sustain his sinking reputation, and recover the fortune he has lost. The communication of the great secret is now the staple commodity with which he is to barter, and the grand talisman with which he is to conjure. It can be imparted only to a chosen few--to those among the opulent who merit it by their virtues, and can acquire it by their diligence, and the divine vengeance is threatened against its disclosure. A process commencing in fraud and terminating in mysticism is conveyed to the wealthy aspirant, or instilled into the young enthusiast, and the grand mystery passes current for a season, till some cautious professor of the art, like Tycho, denounces its publication as detrimental to society. Among the extravagant pretensions of the alchemists, that of forming a universal medicine was perhaps not the most irrational. It was only when they pretended to cure every disease, and to confer longevity, that they did violence to reason. The success of the Arabian physicians in the use of mercurial preparations naturally led to the belief that other medicines, still more general in their application, and efficacious in their healing powers, might yet be brought to light; and we have no doubt that many substantial discoveries were the result of such overstrained expectations. Tycho was not merely a believer in the medical dogmas of the alchemists, he was actually the discoverer of a new _elixir_, which went by his name, and which was sold in every apothecary's shop as a specific against the epidemic diseases which were then ravaging Germany. The Emperor Rudolph having heard of this celebrated medicine, obtained a small portion of it from Tycho by the hands of the Governor of Brandisium; but, not satisfied with the gift, he seems to have applied to Tycho for an account of the method of preparing it. Tycho accordingly addressed to the Emperor a long letter, dated September 7, 1599, containing a minute account of the process. The base of this remarkable medicine is Venetian treacle, which undergoes an infinity of chemical operations and admixtures before it is ready for the patient. When properly prepared he assures the Emperor that it is better than gold, and that it may be made still more valuable by mixing with it a single scruple either of the tincture of corals, or