The folly, the madness, and the wickedness of the alchymists, for their conduct at different times merited each title, continued without any considerable change. They worked in secret; and collected facts which were to supply at a future period the more rational chemists, but had little influence on the practice of medicine till the period of Paracelsus. This visionary of the sixteenth century burnt in solemn state the writings of Galen and his followers, professing to cure all diseases by chemical medicines alone. He was equally depraved in his moral, as he was insolent and ignorant in his medical, character. His precepts were generally dictated in fits of intoxication; and he owned to one of his favoured disciples, that he could not maintain his credit in any place above a year. He died in his forty-seventh year, boasting of having the power of prolonging his life to an indefinite period. From the mysticism of his language, many parts of which Dr. Motherby and his associate had preserved, and some specimens we have, perhaps with too great facility, retained, it will appear that little can be learnt from his works, which however, have been collected by his disciples in two volumes folio. He was succeeded in this path by Van Helmont, equally-visionary as an alchymist, and more so in adopting the fancy of sympathetic medicine; but a man of talents, of observation, and, out of these departments, not without judgment. To Van Helmont, though nearly at the distance of a century from Paracelsus, and to Crollius, we owe the labours of Paracelsus in a more intelligible form; and we are certainly indebted to him for the invention or preservation of some very valuable chemical preparations. The original of Crollius appeared at Frankfort, in 1609, and was translated into English in 1670. Glauber, Kunkel, Kircher, and Conringius, were diligent and experienced chemists, who added greatly to the stock of facts, and to whom we are still indebted.

Chemistry, however, continued to be only a collection of detached facts, without any bond of connection, without any principle of union; nor, until the period of Becher and Stahl, did it assume the semblance of a science. Becher died, like Paracelsus, at the age of forty-seven; but he had collected the various operations of chemistry, and united them by general principles: one of these was the supposition of phlogiston, which has only of late been, with reluctance, abandoned. Stahl, a man of singular talents, of an imagination lively and eccentric, but who wrote with a logical precision almost unexampled, assumed gratuitously the existence of this principle; and connected also, chiefly by its means, the numerous isolated facts of which chemistry then consisted. His cotemporary, Hoffman, applied this science, with more studied care, to medicine, and collected, with great anxiety, the labours of the more intelligent chemists who preceded or were cotemporaries with him. As a medical chemist, Hoffman merits the highest commendation: he was patient, industrious, and honest. He was, however, too eager, certainly too credulous. About the same period, with superior talents and similar faults, our own Boyle laboured in this vineyard; but, while we blame their credulity, we must make allowance for the splendour of numerous and surprising phenomena, which dazzled the imagination, and led the judgment captive. It was a new world, and what they believed was scarcely more extraordinary than what they saw.

To pursue the subject of medical chemistry, our chief object, we shall next mention the celebrated Boerhaave, who detailed, very advantageously, what former chemists had discovered, and added the result of many years unremitted industry. He unveiled the mysteries of the art, by employing the language of learning and philosophy unmixed with metaphor and an assumed obscurity. Probably, no author promoted, more successfully, the progress of chemistry, or applied it more advantageously to medicine; and he advanced it by these means rather than by splendid discoveries. After him followed Dr. Cullen, who, probably, brought to this science those extensive systematic views which distinguished him in every other. But the cold reserve of his descendants, their apparent indifference to his fame, repress all communication. We know only that his lectures were received with great approbation, and that his chemical knowledge was directed to medicinal improvements. To him we are indebted for the more general use, at least, if not the introduction, of some of the more active metallic preparations. Dr. Black followed his steps; and, though he pursued chemistry rather as an independent science, he seldom lost sight of its application to medicine.

In following the systematic authors, we have hastened too rapidly in our way. From the time of Boerhaave to the downfal of Becher and Stahl's boasted principle, numerous were the authors who improved this science. Among the Germans, Neumann, Pott, Cramer, Car-theuser, Margraaf, Spielman, De Born, Plenck, Scheele, and Gren; in Holland, Ingenhouz and Van Mons; in France, the Geoffroys, Reaumur, Du Hamel, Hellot; the two Rouelles, Homberg, Macquer, Baume, Sage, Darcet, and De Morveau; In Italy, Scopoli, Fontana, Liandriani, Cavallo, Volta, and Spalanzani; in England, Hales, Mayow, Lewis, Priestley, Black, Higgins, and Nicholson; in Sweden, Brandt, Wallerius, Cronstedt, Rinman, Scheffer, Gahn, and Bergman. Those who have applied more particularly chemistry to medicine are marked by italics.

The early dawn of chemical improvements may be traced, in England, to the period of Mayow, Hales, Kirwan, and Black, of the old school; from Priestley and Cavendish of the new. Gahn and Bergman, Sage and De Morveau, Scopoli and Spailanzani, are on the confines of each system, and may belong to both. The experiments of Hales and Mayow had been forgotten, when Black elicited the first spark, which was to dazzle with the flame it excited. This embryo, if not neglected, scarcely treated with a parent's fondness, was cherished by Cavendish and Priestley; and the result was the splendid discovery of the composition of water; the existence and properties of many, permanently elastic, gases. Lavoisier, De la Place, Berthollet, and Fourcroy, followed; and from this period the distinguished chemists of every country have resigned the visionary phlogiston, and joined in adopting the pneumatic system. Priestley died an infidel; Gren but half converted. Kirwan and Black joined with apparent reluctance, after patient inquiry and full conviction, what is styled the antiphlogistic system. The revolution is now, we believe, complete: it is not heresy, but reformation.