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 im posing, 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 than 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, may have intended to employ the term chymia, which he simply 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 1630, expressly maintained the absorption of air by metals during their calcination; nor was it much later that Torricelli and Pascal began to investi gate the mechanical properties of the air with mathematical precision. About the time of the foundation of the Academy 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, Hofmann, 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 modifications, from the presence of various effluvia. The error of this opinion was clearly and elegantly displayed by Dr. Black, who published, in 1756, 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 continent 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, 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.' Bayen, 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 phlogis ton 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 simpler 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, Pfaff, 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 seve ral substances, which had never been separated into any other forms of matter in the common processes of experiment, were susceptible of analysis by electrical powers: in consequence of these circumstances, the fixed alkalis, and several of the earths have been shown to be metals combined with oxygen; various new agents have been furnished to che mistry, and many novel results obtained by their application, which, at the same time that 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. Certain bodies, which attract each other chemically, and combine when their particles have freedom of motion, when brought into contact, still preserving their aggregation, exhibit what may be called electrical polarities; and by certain combinations these polarities may be highly exalted; and in this case they become subservient to chemical decompositions; and by means of electrical arrangements, the constituent parts of bodies are separated in a uniform order, and in definite proportions. Bodies combine with a force, which in many cases is correspondent to their power of exhibiting electrical polarity by contact; and heat, or heat and light, are produced in proportion to the energy of their combination. Vivid inflammation occurs in a number of cases in which gaseous matter is not fixed; and this phenomenon happens, in yarious instances, without the interference of free or combined oxygen. Crystals of oxalic acid,' for example, (p. 159,) touched by dry quicklime, exhibit electrical powers; and the acid is negative, the lime positive. All the acid crystals, upon which I have experimented, when touched by a plate of metal, render it positive. And in Voltaic combinations with single plates or arcs of metal, the metal is negative on the side opposed to the acid, and positive on the side or pole opposed to the alkali. Bodies that exhibit electrical effects previous to their chemical action on each other, lose this power during combination. Thus, if a polished plate of zinc is made to touch a surface of dry mercury, and quickly separated, it is found positively electrical, and the effect is increased by heat; but if it be so heated as to amalgamate with the surface of the mercury, it no longer exhibits any marks of electricity.When any conducting substance, capable of combining with oxygen, has its positive electricity increased, it will attract oxygen with more energy from any imperfect conducting medium;*and metallic bodies, that in their common state have no action upon water, such as silver, attract oxygen from it easily, when connected with the positive pole in the Voltaic circuit; and bodies that act upon water, such as zinc and iron, so as to decompose it slowly, refuse to attract oxygen from it, when they are negatively electrified in the Voltaic circuit. Acids, which are negative with respect to alkalis, metals, and earths, are separated from these bodies in the Voltaic circuit at the positive surface; and alkalis, metals, and earths, are separated from acids. at the negative surface: and such are the attracting powers of these surfaces, that acids are transferred through alkaline solutions, and alkalis through through acid solutions, to the surfaces where they have their points of rest. It is easy to show this by making a combination of three agate cups, one containing sulfate of potassa, one weak nitric acid, and the third distilled water, and connecting them by asbestus moistened in pure water, in such a manner, that the surface of the acid is lower than the surface of the fluid in the other two cups. When two wires of platina, from a powerful Voltaic apparatus, are introduced into the two extreme cups, the solution of the salt being positively electrified, a decomposition will take place, and in a certain time a portion of potassa will be found dissolved in the cup in contact with the negative wire, though the fluid in the middle cup will still be sensibly acid.' We must here take the liberty of remarking, that several of these singular effects had been observed by Hisinger and Berzelius in Sweden a year or two before the date of Sir Humphry Davy's discoveries: but they had neither led those chemists to entertain any suspicion of the true laws by which they are governed, nor to apply them to the production of any unknown substances. The first of the remarkable decompositions that our author effected, by means of his newly established principles, was that of potass, or the vegetable fixed alkali, from which he obtained the new metal potassium in October 1807. When a thin piece of pure or caustic potass, in its usual state of a dry hydret, or combination with water, 'is placed between two discs of platina connected with the extremities of a Voltaic apparatus of 200 double plates; it will soon undergo fusion, oxygen will separate at the positive surface, and small metallic globules will appear at the negative surface, which consist of potassium.' It may also be procured by heating iron filings to whiteness in a gunbarrel, and suffering melted potass to come slowly into contact with them, as MM. Gay Lussac and Thénard discovered; and even by strongly igniting potass with charcoal, as Mr. Curaudau has shown. This metal is about one seventh specifically lighter than water; it fuses at about 150° of Fahrenheit, and becomes gaseous below a red heat. It inflames violently when moistened, or when gently heated in contact with the air, affording alkaline fumes. Its powerful attraction for oxygen renders it a very useful agent in chemical analyses: naphtha seems to be almost the only substance in which it can be kept with convenience. Soda, the mineral alkali, affords, when similarly treated, though not quite so easily, a metal much resembling potassium, but a little heavier, though still lighter than water; fusible at about 200°, and evaporating at a strong red heat: our author has very properly named it sodium; it agrees with potassium in most of its properties. Barium was obtained in May 1808, in the form of a dark grey mass, with little lustre, by means of a process suggested by MM. Berzelius E 4 |