lived till 1803 (when she was taken from him by death,) in a happy state of marriage, the fruits of which, three daughters and one son, now survive their parents. He continued in possession of this laboratory, in which he had arranged, for his scientific labours, a small work-room of his own, till the year 1800, when he purchased the room of the academical chemists, in which he was enabled, at the expense of the academy, to furnish a better and more spacious apartment for his labours, for his extremely valuable mineralogical and chemical collection, and for his lectures.

As soon as Klaproth had brought the first arrangement of his office to perfection,-an office which, under his inspection and management, has always been a model of a laboratory, conducted upon the most excellent principles, and governed with exact conscientiousness, there appeared in Crell's Chemical Annals,-in the Writings of the Society for the Promotion of Natural Knowledge,-in Selle's Contributions to the Science of Nature and of Medicine,-in Köhler's Journal, and in other periodical works, a multitude of essays by him, which drew the attention of all chemists, and afterwards gained for him the rank of the first analytical chemist in Europe. Of these labours, we may mention only an Essay on Copal,-on the Elastic Stone,-on the Pearl-Salt of Proust, -on the Green Lead-Spar of Tschoppau, on the best Method of preparing Ammonia,-on the Carbonate of Barytes, on the Wolfram of Cornwall,-on the Wood TinÖre, on the Violet Schorl,-on the celebrated Aerial Gold, -on Apatite, and so forth. All these labours, by means of which scientific chemistry was illustrated and enriched, were gone through before the year 1788, when he was adopted as an ordinary member of the physical class of the Royal Academy of Sciences, the Royal Academy of Arts having elected him one of their members a year before. From this time, not only all the volumes of our academical memoirs, but several of our well known daily papers, contained a multitude of new discoveries by this accomplished chemist; and we must say, that, amidst all this crowd of his works, there is not one by which we have not been led to a more exact knowledge of some one or other of the productions of nature or of art, since in these works he has either corrected false representations, or extended views that were before partially known, or has revealed the internal and formerly unknown composition and mixture of the parts of bodies, and has made us acquainted with a multitude of new elementary substances. Amidst all these labours, it is diffi

cult to say, whether we should most admire the fortunate genius, which in all cases readily and easily divined the point where any thing of importance lay concealed; or the acuteness which enabled him to find out the best means of obtaining his object,-or the unceasing labour, and the incomparable exactness with which he developed it,—or, lastly, the pure scientific feeling under which he acted, and which was removed at the utmost possible distance from every selfish, every avaricious, and every contentious purpose.

He very properly began in 1795 to collect his works, which were dispersed among so many periodical publications, and to edite them under the title of Contributions to the Chemical Knowledge of Mineral Bodies. Of this work, which must always be a classical production in chemical literature, six volumes had appeared by the year 1815. It contains, in no fewer than 207 treatises, the most valuable part of all that Klaproth had done for Chemistry and Mineralogy; and it is to be wished that the profits may so turn out as to lead to the collection of a few essays which still remain dispersed, into a seventh volume, and to the furnishing of the whole with a good index; an undertaking which, to a young chemist, anxious to perfect his knowledge, would be as full of instruction as of pleasure.

Beside Klaproth's own printed works, the interest which he took in several important labours of others, ought not to pass unnoticed. He superintended a new edition of Gren's Manual of Chemistry, with respect to which, however, he did not seek to earn so much merit by what he added, as by what he took away and corrected. But the part which he took in the Chemical Vocabulary, which was edited under his own name, and that of Wolff, was of great importance. For although the composition of every particular article was the labour of the learned Professor Wolff, yet Klaproth took such an active interest in the work, that he read through every important article before it was printed, and assisted the editor, on all occasions, with the treasures of his experience and knowledge. In the German translation, too, of Berthollet on Affinity and on Chemical Statics, the author of the present memoir was much indebted to the revisal of Klaproth.

If the author of this memoir were to collect the merit of Klaproth as a chemist into one great feature, he would place it not so much in the discovery of new metals and earths, as In the invention of more exact and more perfect methods of analysis, than were known before his time. The former

kind of merit is more adapted to draw the attention of the public at large; but the latter is of infinitely greater consequence to science. Passing by the numberless small expedients which Klaproth devised for procuring a more unmixed deposition and separation of all kinds of matters, we only notice at present that he enriched experimental chemistry with two new methods of analysis, which are unlimited in their applications.

The first of these was the complete resolution of the hardest minerals, by means of fluid caustic alkali, instead of the former treatment with dry caustic alkali, which had introduced the use of silver crucibles and saucers into experimental chemistry. The complete resolution of the hardest stones, by this method of analysis, has enabled us to ascertain, with extreme accuracy, the quantity of earths, oxydes, metals, and even of acids, which minerals contain. Exact analyses of this kind remain sure for ever, and are of importance to the science, independent of any discoveries which may be made, respecting the particular nature of the substances mentioned. As, for instance, the capability of being decomposed, which was afterwards discovered to belong to the earths, makes not one cypher incorrect or superfluous in such analysis. The advantage of this method is particularly evident in the decomposition of corundum or diamond-spar. As Klaproth first attempted the analysis of these bodies, by the former method of decomposition, he found a considerable remainder of matter unaccounted for. On the suspicion, which he then expressed, that this remainder might perhaps be a new, and yet undiscovered earth, many compilers of school books were in a hurry to admit the earth of corundum into the list of the simple earths. But when Klaproth repeated the analysis, by means of the liquid alkali, he found that this substance was one of the many compositions of siliceous and argillaceous earths, which had not previously been known, and which in former analyses had sometimes been referred to the one kind of earth, and at other times to the other. In the same manner, the chemists of England gave an account of a species of sand, which had been brought from New Holland, as a new earth; but Klaproth shewed, by his new method of analysis, that this body also, which had already been introduced into introductory treatises, under the name of "the Austral Earth," was nothing but an intimate mixture of siliceous and argillaceous earth. Indeed, the first analyses that can be considered as certain, are those which have been undertaken on this plan. Hence, by this

discovery, almost all the more early analyses have lost their value. Of what inestimable moment such a discovery must be, not merely to experimental chemistry, but to the whole. of the science of nature, even although Klaproth had not discovered by means of it a single unknown body, does not require to be more particularly stated. In the numerous exact analyses which Klaproth conducted according to this method, there was almost always discovered at last to be a small loss, that is to say, the weight of all the single component parts was ascertained to be somewhat less than the weight of the mineral which had been analysed. He in every case stated this loss with great precision, and by this incorruptible regard to truth, he obviously procured for the results of his labours a much greater certainty than if he had permitted himself, as he might easily have done, to conceal this loss under inconsiderable changes in the decimal figures. He also never gave his results, as he likewise easily might have done, in a great crowd of decimals, by which means the appearance of much exactness is sometimes gained, but he gave only as many cyphers as were sure. As long as the loss amounted only to a few thousand parts of the whole, it might easily be referred to those small mistakes which in every course of experiments are unavoidable, from the limited nature of our senses and instruments. But, in some analyses, as, for instance, in that of Felspar, a loss of some hundred parts was discovered. Such a loss, considering the care with which Klaproth laboured, could only arise from some of the constituent parts having entirely escaped observation during this method of resolution. Convinced that this could be neither an earth nor a metal, nor an acid, nor water, nor any other volatile matter, he at last began to suspect that perhaps many minerals might contain a hitherto unsuspected quantity of fixed alkali, which could not be discovered by the method of analyses by means of these alkalies. This consideration led to Klaproth's second great invention, I mean, the method of analysis by means of Barytes, although, as was formerly remarked, the excellent Rose had no inconsiderable part in this invention. The event justified Klaproth's suspicion, since he actually discovered a considerable quantity of fixed alkali in felspar, porphyry-slate, and many other minerals.

By the union of these two effective methods of analysis, Klaproth has in fact brought the art of chemical analysis to such a degree of perfection, that we are entitled to expect, not only that all the fundamental constituents of minerals,

but even their relative qualities, will, by degrees, be determined with perfect correctness. But he not only laid the foundation of this reform; he has even reared a great and considerable portion of the superstructure. His analyses have hitherto been found so correct, that even in the most careful repetitions of them, whether with or without any change of the method of resolution, only inconsiderable variations have been found. And, although, as has been done lately by some celebrated natural historians, great improvements have been suggested merely upon hypothetical views, yet we are bound to demand that the mistake should first be pointed out by experimental investigators. Facts are the only sure foundation not only of chemistry, but of all science without exception. Even mathematics and philosophy are no exceptions to this; for they must rest on the facts of natural consciousness, if they are at all well founded. Hypothetical views are indispensable for the promotion of truth: but it is clear that they can never furnish a firm foundation of science. Wherever, therefore, there is an evident opposition between a hypothesis and facts, our first duty is to examine whether the foundation can be so cleared out as to evince either the incorrectness of the supposed facts or of the hypothesis. But if the foundation cannot be so cleared out, the suspicion of incorrectness must then fall upon the hypothesis, until some mistake as to facts has been proved.

It is hence not to be doubted, that even distant posterity will honour the merits of this distinguished man, who has not merely examined and explained a greater number of facts than perhaps any other chemist, but who, more especially by the methods of analyses proposed by him, as well as by his own excellent models of proceeding, has shewed naturalists the way by which they may enrich science with new facts, and may render those that are already known still more perfect and exact. The great care which Klaproth employed in securing the neatness of his experiments, was not the least of his merits, not only because the great confidence which his labours deserve rest chiefly upon this circumstance, but also because in this he was a pattern to all practical chemists.

To this quality must be referred the attention which he bestowed on his instruments. When he had to do with very hard minerals, he used a mortar of flint, but he previously analysed it, and did not neglect the small and scarcely perceptible increase of weight which the matter under examination derived from continued rubbing, and, according to the