« ΠροηγούμενηΣυνέχεια »
gress, may console himself with reflecting that every day is taking from his difficulties, and that he may ultimately hope to receive a version which, with the original at his elbow, he may possibly find intelligible in more places than, from the present attempt, he has any encouragement to expect.
Art. IV. Elements of Chemical Philosophy. By Sir Humphry
Davy, LL. D. Sec. R.S. Prof. Chem. R. I. and B. A. M. R.I. F.R.S. E. M.R. I. A. M.R. A. Stockh. Imp. Med. Chir. Ac. St. Pet. Am. Phil. Soc. Hon. Memb. Soc. Dubl. Manch. Phys. Soc. Ed. Med. Soc. London. Part I. Vol. I. pp. 530. Ten Plates. 8vo. London. 1812. IN attempting a review of this work, we cannot avoid professing,
that we are far from entertaining the impression of sitting down as competent judges, to decide on the merits or demerits of its author: on this point the public voice, not only within our own islands, but wherever science is cultivated, has already pronounced too definitive a sentence, to be weakened or confirmed by any thing that we can suggest of exception or approbation. Our humble labours, on such an occasion, must be much more analytical and historical than critical; at the same time we are too well acquainted with the author's candour, to suppress any remark which may occur to us, as tending to correction or improvement. It has most assuredly fallen to the lot of no one individual to contribute to the
progress of chemical knowledge by discoveries so numerous and important as those which have been made by Sir Humphry Davy: and with regard to mere experimental investigation, we do not hesitate to rank his researches as more splendidly successful, than any which have ever before illustrated the physical sciences in any of their departments. We are aware that the Optics of Newton will immediately occur to our readers as an exception; but without attempting to convince those who may differ from us on this point, we are disposed to abide by the opinion, that for a series of well devised experiments and brilliant discoveries, the contents of Davy's Bakerian Lectures are as much superior to those of Newton's Optics, as the Principia are superior to these, or to any other human work, for the accurate and refined application of a sublime and simple theory to the most intricate and apparently anomalous results, derived from previous observation.
Discoveries so far outshining all that has been done in other countries, and constituting so marked an era in the history of chemistry, cannot be contemplated by any Englishman, who possesses a taste for science, without some degree of national, and even local exultation; although it is true that other individuals, and other VOL. VII, NO, XV.
countries have contributed largely to the success of the common cause; some, by improving the principles of other departments of physics which bave been so happily applied, or by furnishing the most powerful agents and the most convenient instruments, which have been employed with so much address; and others by collateral or independent speculations and researches, which have here been blended together into one system.
From all these sources our author has derived the materials of a volume, which, when compared even with the latest works of a siinilar nature, exhibits a more rapid and triumphant progress of improvement than can be paralleled in the annals of human invention. He has adverted, with a very laudable modesty, to the favourable circumstances under which his researches were conducted :
Nothing tends so much,' he observes, to the advancement of knowledge as the application of a new instrument. The native intellectual powers of men in different times, are not so much the causes of the different success of their labours, as the peculiar nature of the means and artificial resources in their possession. Independent of vessels of glass, there could have been no accurate manipulations in common chemistry: the air pump was necessary for the investigation of the properties of gaseous matter; and without the Voltaic apparatus, there was no possibility of examining the relations of electrical polarities to chemical attractions.'
It must, however, be remembered, that almost every other discovery of importance, which has been made in science, has been facilitated by some previous steps, which bave rendered practicable what might otherwise have presented insuperable obstacles to human ingenuity; nor bas such a preparation ever been allowed to detract from the just applause, bestowed on those who bave been distinguished froin their contemporaries by a more successful exertion of talent.
Until the year 1806, Sir Humphry Davy had been remarkable for the industrious and ingevious application of those means of experiment only, which had been long known to chemists; he had acquired, at a very early period of his life, a well established celebrity among men of science throughout Europe, by the originality and accuracy of his researches; and at the same time the fluent and impressive delivery of his lectures had obtained him the most fattering marks of approbation from the public of the metropolis. But it was in the summer of this year, that in repeating some electrochemical experiments of very doubtful authority, he was led into a new train of reasoning and investigation, which enabled bim to demonstrate the important laws of the connexion between the electrical affections of bodies and their chemical powers. This was his first great discovery: and when he was complimented on the occa
sion by the Institute of France with the prize established by Buonaparte, it was only questioned, by those who were capable of appreciating its importance, whether they acted with strict impartiality in assigning to him the annual interest only; while he appeared to have a fair claim to the principal, which was allotted, by the donor, to the author of a discovery relating to electricity, paramount to that of Franklin or of Volta. Our author's next great step was the decomposition of the alkalis, which he effected the succeeding year; and this, though less interesting and important with regard to the fundamental theory of the science, was more brilliant and imposing, from its capability of being exhibited in a visible and tangible form. The third striking feature, which distinguishes the system advanced in the present work, is the assertion of the existence of at least two empyreal principles; oxygen, and the elastic fluid called the oxymuriatic acid gas, being considered as possessing equal claims to the character of simple or undecompounded substances. A fourth peculiarity, which, however, is less exclusively and originally a doctrine of Sir Humphry Davy, is the theory of the simplicity of the proportions in which all bodies combine with each other; a theory respecting which hints may be found in the works of several chemists of the last century, but for the explicit illustration, and general and minute application of which, the science is principally indebted to our countryman Mr. Dalton; although the work before us tends much more to its confirmation any
other mass of evidence which has yet been collected on the subject. On each of these four principal novelties we shall make some extracts and abstracts; having first given a hasty outline of the interesting sketch of the progress of chemistry which constitutes the introduction.
We shall not attempt to follow our author in his inquiries how far any of the Arabian physicians or magicians may be said to have been the founders of the science of chemistry, rather than the Greeks or Egyptians, or even to conjecture in what sense Firmicus, whom he has not mentioned, inay have intended to employ the term chymia, which he sinıply introduces as a science or mystery: but contenting ourselves with enumerating the names of Roger Bacon and Basil Valentine, as the greatest chemists of the 13th and 15th centuries, and Paracelsus, Agricola, and Libavius, of the 16th, we shall hasten to the beginning of the 17th, as the true period of the commencement of the pneumatic chemistry, under the auspices of Van Helmont, who first distinctly observed the properties of several elastic fluids, which he denominated gases ; and more especially of Rey, who, in the year 1650, expressly maintained the absorption of air by metals during their calcination; por was it much later that Torricelli and Pascal began to investi
gate the mechanical properties of the air with mathematical preci
About the time of the foundation of the Acadeiny del Cimento, of the Royal Society, and the Parisian Academy of Sciences, which constitutes an era so important in the progress of human knowledge, the most distinguished chemists in Germany were Glauber, Kunckel, Brandt, Hofmam, Beccher, and Stahl; in France, Homberg, Geoffroy, and the Lemerys; and in England, Boyle, Hooke, Slare, and Mayow; but with regard to the philosophical theory, especially of pneumatic chemistry, the English had advanced far beyond their neighbours, even before the publication of the correct and comprehensive speculations contained in the queries of Newton, which marked the commencement of the 18th century, and which may be considered as the basis of the more refined and accurate cultivation of chemical science. In pursuit of these suggestions, the order of chemical attractions appears to have been first distinctly exhibited in a tabular form by Geoffroy, about the year 1718. The idea of a single combustible principle, or phlogiston, is traced to Albertus Magnus, the contemporary of Roger Bacon, and was received from Beccher by Stahl, who advanced in support of it many ingenious experiments; for example, the decomposition of Glauber's salt by charcoal; and this doctrine was almost universally adopted throughout Europe, in preference to the more correct views of Boyle, Hooke, and Mayow. The researches of these chemists were, however, in some degree revived by the industrious Dr. Hales, although he was unfortunately misled by the idea, that all elastic fluids were essentially the same, and only distinguished by some accidental moditications, from the presence of various effluvia. The error of this opinion was clearly and elegantly displayed by Dr. Black, who published, in 1750, a little essay on magnesia and fixed air, which may be considered as the true beginning of the pneumatic chemistry. The earliest labours of Mr. Cavendish are dated in 1765, when he invented the hydropneumatic apparatus, discovered inflammable air, and made many very important experiments on the properties of gases of different kinds. "Dr. Priestley followed the steps of Hales and Cavendish with the most distinguished success, and discovered the existence of nitrous gas, nitrous oxyd, and oxygen; and exhibited, by means of the mercurial apparatus, muriatic acid, sulfurous acid, and ammonia, in a gaseous state. Macquer, Rouelle, Margraff, Pott, and above all Bergman, were in the mean time diligently pursuing their refined analyses on the con: tinent: and Scheele was carrying on a train of investigations much resembling those of Priestley; ascertaining the composition of the atmosphere, and the properties of the fluoric and prussic acids, and the oxymuriatic acid gas. Of all these chemists, Black, Ca
vendish, Priestley, and Scheele were unquestionably the greatest discoverers: the facts, which they had brought forward, were in some measure systematized by Lavoisier, to whom our author thinks that no other inquirer except Cavendish can be compared for precision of logic, extent of view, and sagacity of induction. Baven, in 1774, had shown that the calx of mercury was capable of being rendered metallic, without the addition of any inflammable substance, and hence had argued against the agency of phlogiston in the revival of metals in general. In the next year, Lavoisier examined the air afforded by the calx during its reduction, which was already known to Priestley and Sheele, and called it oxygen: he demonstrated also the constitution of the carbonic acid gas, and showed that the nitrous and sulfuric acids derive their properties from the combination of their bases with oxygen : Mr. Cavendish soon after showed the true nature of the basis of the nitric acid, and made a discovery, which is perhaps of greater importance than any single fact which human ingenuity has ascertained, either before or since, that of the composition of water from oxygen and hydrogen. Soon after this, Mr. Berthollet proved that ammonia consists of hydrogen and nitrogen; and many other chemists continued a series of researches, which appeared to illustrate and confirm the doctrine of Lavoisier : the existence of phlogiston was, however, still very ably maintained by Mr. Cavendish in 1784, as the simples of the two theories by which the phenomena might be explained; and other chemists retained the same opinion for a much longer period. In 1787, the French chemists presented to the public their new system of nomenclature, which certainly contributed in some degree to the facility of acquiring the science, but still more to the dissemination of the doctrines of the school from which it proceeded.
• At the time (p. 53.) when the antiphlogistic theory was established, electricity had little or no relation to chemistry. The grand results of Franklin, respecting the cause of lightning, had led many philosophers to conjecture, that certain chemical changes in the atmosphere might be connected with electrical phenomena ; and electrical discharges had been employed by Cavendish, Priestley, and Vanmarum, for decomposing and igniting bodies; but it was not till the era of the wonderful discovery of Volta, in 1800, of a new electrical apparatus, that any great progress was made in chemical investigation by means of electrical combinations,
• By researches, the commencement of which is owing to Messrs. Nicholson and Carlisle, in 1800, which were continued by Cruickshank, Henry, Wollaston, Children, Pepys, Pfatt, Desormes, Biot, Thénard, Hisinger, and Berzelius, it appeared that various compound bodies were capable of decomposition by electricity; and experiments, which (says our author) it was my good fortune to institute, proved that seveE 3