fallacious: he simplified the operations, and introduced new and convenient apparatus for the purpose. Nor ought we to pass over in silence the curious results of his experiments on the quantity of nutritive matters contained in varieties of the different substances that have been used as articles of food, either for men or for cattle, by which he was enabled to explain numerous facts connected with the comparative excellence of different articles. Thus, for instance, in the south of Europe, hard, or thin-skinned wheat, is in higher estimation than soft, or thick-skinned wheat; a fact which he showed to depend upon the larger quantity of gluten and nutritive matter which the former contains.

In the year 1803, Davy was elected a Fellow of the Royal Society; he subsequently became its Secretary, and lastly its President. During a period of five-and-twenty years, he constantly supplied its Transactions with papers; and it is not too much to say, that no individual philosopher, in any age or country, ever contributed so largely in extending truth, or ever achieved so much in eradicating error. The theory of Lavoisier, which was received throughout Europe with the homage due to an oracle, and was even classed in certainty with the doctrine of gravitation-which had withstood all the assaults of the Stahlian philosophers, in Germany, Sweden, and Britain, and passed unimpaired through the most severe ordeals to which any system was ever exposed-yielded, in some of its most essential points, to the cool and dispassionate reasoning of Davy. It is impossible not to admire the candour and humility with which Davy alludes to the circumstance; in speaking of the experiments which it was "his good fortune to institute," he says, "the novel results, while they have strengthened some of the doctrines of the school of Lavoisier, have overturned others, and have proved that the generalisations of the Antiphlogistic philosophers were far from having anticipated the whole progress of discovery."

As the advantages afforded by the history of any great scientific discovery, consist as much in exhibiting step by step, the intellectual operations by which it was accomplished, as

in detailing its nature, or in examining its relations with previously established truths, so must it prove highly interesting to fix the period at which Davy's mind was first directed to the subject of Voltaic electricity. In referring to the " Additional Observations," appended to his "Chemical Researches," it appears that he had no sooner heard of the curious experiments of Volta upon the effects produced by the contact of two inorganic bodies, than, with his characteristic quickness of perception, he proceeded to enquire whether the fact, previously noticed by himself, of the conversion of nitrous gas into nitrous oxide by exposure to wetted zinc, might not depend upon Galvanic action. It was the early habit of his mind, not only to originate new enquiries, but without delay to examine the novel results of other philosophers; and in numerous instances it would seem that he only required to confirm their accuracy, before he succeeded in rendering the application of them subservient to further discovery.

In examining the numerous memoirs which he presented to the Royal Society, it is impracticable to preserve their chronological succession, without losing sight of that fine intellectual thread by which the mind of their author was conducted through the intricate labyrinths of nature: we shall therefore, in the first place, present to the reader a brief analysis of those several memoirs, in which the laws of electricity have been so profoundly investigated, and its chemical agency so successfully and beautifully displayed in the separation of the elements of hitherto undecompounded bodies. It is impossible to enter upon the subject of galvanic electricity, without recurring to the circumstance which first demonstrated the existence of such an energy, and to the sanguine expectations which it excited. It was natural to believe, when we witnessed the powerful contraction of a muscular fibre by the contact of a metal, that the nature and operation of the mysterious power of vital irritability would be at length developed by a new train of research. It is a curious fact, that an experiment so full of promise to the physiologist should hitherto have failed in affording him any assistance; while,

the chemist, to whom it did not appear to offer one single point of interest, has derived from it a new and important instrument of research, which has already, under the guidance of Davy, multiplied discoveries with such rapidity, and to such an extent, that it is impossible to anticipate the limits of its power. Here, then, is another striking instance of a great effect produced by means apparently insignificant. Who could have imagined it possible that the spasmodic action produced in the limb of a frog, by the accidental contact of a pair of scissors, should have been the means of changing the whole system of chemistry, — of discovering substances whose very existence was never suspected, of elucidating the theory of volcanoes and earthquakes, and, may we not add, of leading the way to a knowledge of the laws of terrestrial magnetism? Such an unexpected extension of an apparently useless fact, should dispose us to entertain a kinder regard for the labours of one another, and teach us to judge with diffidence of the results of science. A discovery which may appear incapable of application to-day, may be our glory tomorrow, and even wield the destiny of nations. The conic sections of Apollonius Pergæus remained useless for two thousand years: who could have supposed that, after the lapse of twenty centuries, they would have formed the basis of astronomy, a science giving to navigation safety, guiding the pilot through unknown seas, and tracing for him in the heavens an unerrring path to his native shores! It has been well said by the accomplished author of Lettres à Sophie : "L'histoire des grand effets par les petits causes ferait un livre bien curieux."

The first memoir presented to the Royal Society by Mr. Davy, was read on the 18th of June 1801; and is entitled, "An Account of some Galvanic Combinations, formed by the Arrangement of Single Metallic Plates and Fluids, analogous to the new Galvanic Apparatus of Volta; by Mr. Humphry Davy, Lecturer on Chemistry in the Royal Institution; communicated by Benjamin, Count of Rumford, V.P.R.S." In order to appreciate the value of this paper, it must be remem

bered, that the agencies of two metals in exciting Galvanic phenomena were at that time supposed to be directly connected with the different powers of such metals to conduct electricity. Davy was the first philosopher who corrected this error, and, in the paper before us, showed that the evolution of galvanic energy was connected with chemical action; an inference which he deduced from some experiments, by which he found that an accumulation of Galvanic influence (exactly similar to that in the common pile, where two metals are used) might be produced by the arrangement of single metals, with different strata of fluids. This theory he established by a great variety of experiments, and showed that the alternation of two metals with fluids was no further necessary to the production of accumulated galvanic influence, than as it furnished two conducting surfaces of different degrees of oxidability; and that this production would take place, if single metallic plates were connected together by different fluids, in such a manner that one of their surfaces only should undergo oxidation, the arrangement being regular. He moreover ascertained that many of these arrangements could be made active, not only when oxidation, but likewise when other chemical changes were going on in some of their parts. Here, then, appeared the dawn of the electrochemical theory. The main fact stated in Davy's paper, namely, the relation between the energy of the pile and the oxidation of one of its metals by the interposed fluid, was readily admitted; but a question arose, whether the oxidation, instead of being the primary cause, might not be the effect of the electricity, set in motion by the contact of metals, endowed with different conducting powers. Upon this occasion, with an alacrity corresponding with the importance of the subject, Dr. Wollaston appeared in the arena, and at the meeting succeeding that at which Davy's paper was read, related to the society a series of experiments, which fully confirmed the views of Davy, and set the question for ever at rest. This fact illustrates some of the most prominent features in the scientific character of Wollaston, the quickness of his perception, the solidity of his judgment, and, above

they, at least, by turning up and pulverising the soil, rendered it fertile.

Such were the circumstances that first extricated Davy from the obscurity of his native town, and paved the way to an eminence which but very few philosophers in this or any other country have been able to attain. Davy was now constantly engaged in the prosecution of new experiments; in the conception of which, as he himself candidly'informs us, he was greatly aided by the conversation and advice of his friend Dr. Beddoes. He was also occasionally assisted by Mr. W. Clayfield, a gentleman ardently attached to chemical pursuits, and whose name is not unknown in the annals of science; indeed it appears that to him Davy was indebted for the invention of a mercurial air-holder, by which he was enabled to collect and measure the various gases submitted to examination. In the course of these investigations, the respirability and singularly intoxicating effects of nitrous oxide were first discovered; which led to a new train of research concerning its preparation, composition, properties, combinations, and physiological action on living beings; enquiries which were extended to the different substances connected with nitrous oxide, such as nitrous gas, nitrous acid, and ammonia; when, by multiplying experiments, and comparing the facts they disclosed, Davy ultimately succeeded in reconciling apparent anomalies; and, by removing the greater number of those difficulties which had obscured this branch of science, was enabled to present a clear and satisfactory history of the combinations of OXYGEN and NITROGEN.

These interesting results were published in a separate volume, entitled "Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide and its Respiration; by Humphry Davy, Superintendant of the Medical Pneumatic Institution." Of the value of this production, the best criterion is to be found in the admiration which it excited: its author was barely twenty-one years old, and yet, although a mere boy, he was hailed as the Hercules in science, who had cleared an Augean stable of its impurities. In a majority of