The French chemists, not content with this splendid improvement, of which, indeed, they could not claim the honour, though they have made numerous additions, scarcely less valuable, perhaps, than the first discoveries of Black and Cavendish, have changed, in consequence of the establishment of the pneumatic system, the whole language of chemistry. They have thus attempted to make it exclusively their own. This vanity, so common in their nation, might excite a smile as harmless; and from the merits, on the whole, of the new nomenclature, command approbation, were it not from some serious inconveniences that will be found to result. At this time, the language of both sects is common, and little inconvenience is experienced; but, except to the experienced chemist, the labours of Pott, of Neumann, of Margraaf, Macquer, Baume, etc. will be soon lost. Their language will no longer convey ideas; and experiments, most truly important and valuable, will be almost on a footing with Egyptian hieroglyphics. There is one remedy for this evil, which is the unmerciful pillage of French authors from their predecessors; and, as usual, the stolen goods are marked with the characteristics of their present owners, to conceal the depredations. This, however, is not sufficient: juvat integros accedere fontes; and, unfortunately, the streams are polluted. Various are the changes we have witnessed to adapt former facts to the theory of the moment. We would strenuously advise the student, therefore, to study the language of both sects; and the lately published lectures of Dr. Black are admirably adapted for this purpose. Mr. Nicholson's Elements also, published when the new theory was not fairly established, contains the explanation of the phenomena according to each system, and will answer the same purpose, though the new theory has received considerable improvement since the period of their publication.

Chemistry, so far as it relates to medicine, has been hitherto employed in the composition of medicines. In this branch, however, previous to the introduction of pneumatic chemistry, much was empirical and heterogeneous; ingredients, destructive of each other's powers.

3 G2 were ignorantly or inconsiderately accumulated. It was the object to heap a great variety of medicines in one formula, that should one fail, another might succeed: forgetting that, though the imagination was boundless, the stomach was limited; and that, when the number of ingredients was increased, the dose of each was inconsiderable. In chemical formulae, the error was greater from the union of heterogeneous substances; and, where the ingredient was retained, its utility was not understood. A striking instance of this kind was the chalybeate oxide in the preparation of the corrosive sublimate, which furnished the pure air that distinguishes this preparation. In the former case we have refined, perhaps, too far, as we shall show in the article of Combination of medicines. In the latter, we have not been equally rash, yet we suspect we have often erred. In the articles, Argentum vivum, and Antimonium, we have shown that the more simple modern preparations are different, in some respects, from those of the ancients. Chemistry, however, which first led the pharmaceutist from the path, will contribute to his recovering it.

In another branch, chemistry was seemingly misemployed; we mean in investigating the powers of medicines. The older chemists employed fire, almost exclusively; and vegetable remedies, the most opposite in their nature, yielded nearly the same products. Even bread, we are informed by Mr. Boyle, will produce, by distillation, the most acrid deleterious oil. In fact, in these destructive processes, new combinations are formed; and, as the principia proxima of vegetable substances are nearly the same, it is not surprising that the products in their reunion, after separation, should be similar. Modern chemistry employs less violent means, and new compounds are not so frequently produced. By these more gentle means, also, the analysis of mineral waters is much more accurate and satisfactory.

This science has, however, since the discovery of new gases, been very successfully employed in investigating the nature, of the animal solids and fluids. A new era may be thus marked in our chemical physiology. They were not neglected by the French chemists, particularly the Rouelles, Homberg, and others; but we have only of late witnessed the happy results of more accurate, more scientific investigation. Since the period of Plenck, whose Hydrology is still an excellent work, we have received considerable satisfaction from Berthollet, Fourcroy, Vauquelin, Pearson, Hatchett, and many chemists of the new school.

To teach chemistry cannot be our object; we must treat of it as the handmaid, the assistant, of physic and the physician, and the chief details must be sought in the different articles. Yet, perhaps, we may here, with advantage, sketch the outline of the science; point out the mutual dependencies of each part, and supply what omissions may have already occurred. We must, however, speak chiefly of medical chemistry; for we anxiously wish to avoid stepping beyond the line of medicine, and to reader this dictionary strictly, and, as far as possible, exclusively a medical one.

In teaching chemistry, modern authors have begun with elements, and proceeded to their compounds. We thus soar, perhaps, too far above common comprehensions, and certainly beyond the youthful intellect. We shall prefer the division of Dr.black, originally that of Dr.

Cullen; and divide the objects of chemistry into salts, earths, inflammables, metals, and waters, adding the airs, vegetable and animal substances. We obtain, however, the bases of every body most pure in the form of air, so that we shall premise a short abstract of the properties of the different gases. Of caloric we have already spoken: of light, as a chemical principle, we know little, and still less of its real influence in the animal economy; yet, under that article, we shall add a few observations on the subject not wholly uninteresting.