whilst in action, might be compared with an inexhaustible Leyden phial, always capable of giving shocks, of producing the phenomena of heat and light, and of operating various chemical changes of an extraordinary kind. It decomposed water and acids, and metallic salts, and, what is very remarkable, the separated elements of water were not evolved together, but maintained their distinct places; the hydrogene at the part determined to be the negative extremity, and the oxygene at the positive end. The power, too, was found identical with common electricity, differing merely in degree, not in kind, and just the same as that possessed by the torpedo. Like common electricity, it gave the shock, produced heat and light, melted metals, and passed imperceptibly over their surfaces; was stopped by glass, silk, and similar substances, and might be transferred to a glass jar, and there confined. We need not state that common electricity was found capable of producing similar chemical changes.

To no one is Voltaic electricity so much indebted as to Sir H. Davy for the discovery of its principles of action, and for the application of it, as an instrument of research to chemical analysis. He detected the errors of Pacchioni and Sylvester, who had asserted that, by the operation of electricity, muriatic acid and fixed alkali were formed on the decomposition of water; and he exploded their notions, that the muriatic, oxymuriatic, and nitric acids, as well as the volatile and fixed alkalies were all of similar origin, and merely different oxides of hydrogene. He proved that the alkalies and acids they had supposed to be generated, were previously existing in the substances employed in the experiments, and only produced. He proved, at the same time, that the decomposing powers of the Voltaic battery are so energetic, that the firmest rocks, the hardest minerals, and most vehement chemical affinities, are incapable of resisting them, and that the smallest quantities are within the scope of its power. He thus drew out from rocks and salts, from animal and vegetable substances, their constituent parts, and detected some of their minutest ingredients. He determined various laws respecting electrical action and chemical decomposition; as, that inflammable and metallic substances, that earths, alkalies, and metallic oxides, are attracted by the negative extremity or pole of the battery, being themselves positive; that oxygene, chlorine, and acids, are attracted by the positive pole, because they themselves are negative; that chemical attractions are put to rest or destroyed by superior electrical attractions; and that bodies may be transferred, without interruption, from one pole to another even through fluids, having natu

rally a strong chemical attraction for them. These views, which first appeared in his publications in the Philosophical Transactions, are again developed and illustrated in his "Elements of Chemical Philosophy," together with the theory of the action of the Voltaic battery. Which action he does not attribute primarily to chemical changes, but to the contact of the different metals and fluids.

The more clearly to convey a notion of his theory, we shall have recourse, as he has done, to the common electrical machine. When' a body that is a non-conductor is brought into the neighbourhood of the prime conductor, it acquires two electrical states, or “polarities," as our author expresses it: the negative one is that nearest the positive conductor; the positive one is that most remote. The same occurs in respect to the Voltaic battery, when pieces of steel wire are placed in water; connected with a powerful combination, they separately acquire polarities, as if they were influenced by a powerful magnet; they arrange themselves with their postive poles farthest from the positive pole of the battery, and the negative nearest, and they acquire similar powers of chemical decomposition. These facts are readily applicable to the action of the battery. The battery does not differ from the electrified wires, but in having within itself the source of its own electricity, instead of possessing a borrowed power. Each pair of metals is analogous to one wire; one of the pair is positive, the other negative. Sir H. Davy supposes the water to be capable of becoming electrically polar, and one part of it, viz. that extremity of a particle which is nearest the positive metal acquires negative polarity, and the other part, in consequence, acquires positive polarity; while the different series of metals so influence each other, that the power of the whole combination increases with the number and surface of the plates.

Though electrical action is not primarily dependent on chemical changes, as the early enquirers imagined, yet are they intimately connected, as appears from the impossibility of preserving a permanent action of the battery without the assistance of chemical agents, and from the circumstance that those substances excite the battery most powerfully, which act on the metals most rapidly. The explanation offered by Sir H. Davy is, that the tendency of electrical action is to return to its equilibrium; and that the tendency of chemical action is to destroy this equilibrium. Thus, when a communication is made between the negative and positive cylinders of a common electrical machine, there is an immediate rest or cessation of all action; and in a similar way the Voltaic battery would cease to act when its extremities are joined, were it not for the chemical

changes taking place: oxygene and chlorine, and acids themselves. negative bodies, are attracted by the positive metallic surfaces, and hydrogene and alkalies themselves positive, are attracted by the negative metallic surfaces; those individuals capable of entering into combination with the metals, unite with them, and the electrical equilibrium is momentarily restored; but the combinations formed being soluble in the water, are removed from the metals; and the gasses evolved being thus disengaged, the equilibrium of electricity is again disturbed, and the electrical action continued.

Our author in a satisfactory manner accounts for the fact, that the action of a battery on imperfect conductors, such as water, the human body, and similar substances, increases with the number of plates; whilst its action on perfect conductors increases with the size of the plates. Those imperfect conductors, it is said, can only discharge a very minute quantity of electricity, probably not more than the smallest battery possesses; therefore, they are only affected by a difference of intensity, and the greater the intensity of the electricity is, the more they are affected; but the intensity or the energy of the electrical polarities is independent of quantity of surface, and is proportionable only to the number of pairs of plates. On the other hand, the perfectly conducting metals are capable of discharging large quantities of electricity, consequently they are affected by the quantity; and as the quantity is proportionable to the surface, the effect of a battery on perfect conductors will be proportionate to the surface. important principles Sir H. Davy has explained at length in his Elements, and proved and illustrated the hypothesis by a series of happy experiments. He has endeavoured to determine the exact ratio in which the intensity of the battery and the quantity of electricity increase with the number of similar plates, and also the tio of increase of quantity with the increased size of the plates. And from experiments apparently admitting of much accuracy, he concludes, that the intensity of the battery is as the square of the number; that the quantity of electricity is as the number of equal plates; but that the quantity or power of acting on perfect conductors is in a very high ratio with the increased surface, probably higher than even the square.

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Sir H. Davy observes, that "electrical effects are exhibited by the same bodies when acting in masses, which produce chemical phenomena when acting by their particles; it is not therefore improbable, that the primary cause of both may be the same, and that the same arrangements of matter, or the same attractive powers, which place bodies in the relations of positive and negative, i. e. which render them attractive of each other

electrically, and capable of communicating attractive powers to' other matter, may likewise render their particles attractive, and enable them to combine when they have full freedom of motion." This ingenious speculation, which the author justly complains has been attacked and misrepresented by those who did not understand his views, has good analogies in its favour. Heat and light are the common effects of strong electrical and chemical action. Those bodies, which in masses most powerfully excite each other electrically by contact, when their particles have freedom of motion, most readily combine chemically, as the acids and alkalies; the metals and sulphur :-and when the natural electrical state of a body is artificially exalted, its chemical attraction also is exalted, and when the former is destroyed, the latter too is no longer exerted. No finer illustration can be given of these truths than the effects attending the action of the Voltaic battery.

Sir H. Davy has used this instrument with the greatest success, and by opposing the superior electrical attractions to the natural chemical ones, he has penetrated into the composition of various bodies, that had long baffled all research. By the same methods, from the fixed alkalies which are well known to be corrosive, dull, and very soluble substances, he has extracted bodies of metallic lustre, exhibiting the colour and splendour of silver, and like metals, perfect conductors of heat and electricity. They are, nevertheless, the lightest bodies in nature, and the most inflammable substances known: the basis of potash takes fire on water and ice, and both of them decompose all bodies known to contain oxygene; so that no little ingenuity of contrivance was necessary to preserve them, and prevent their return to their original state by the absorption of oxygene. The discoverer of these bases of the fixed alkalies considers them as metals, and has accordingly called them potassium and sodium. But his views and his names, though now generally adopted, have met with some weak opposition from those on whom the extraordinary features of the new bodies made the deepest impression-namely, their lightness and inflammability connected with their alkaline origin. We must acknowledge, that his reasons for this classification appear to us perfectly conclusive. It is founded on obvious analogies of the most decisive character. Were minute differences to be taken into account, there would be as many classes of bodies as there are now individuals. The principle of scientific arrangement, is to go from the more general or common properties to those which are less common and particular, and thus kingdoms, classes, orders, &c. are arrived at. To determine the propriety

of Sir H. Davy's classification, we must enquire what are the characters essentially constituting the class of metals. Certainly those are not the properties to seize in making a classification, which are constantly varying, and are different in almost every individual, as colour and specific gravity; but those which uniformly exhibit themselves in all metals, as opacity, the metallic lustre, the power of freely conducting electricity and caloric, and the power of forming chemical combinations with certain substances. If these latter are considered essential characters to the exclusion of the former, as we do not hesitate in asserting that they should be, no doubt will remain respecting the metallic nature of the bases of the fixed alkalies: and there is no less propriety, we conceive, in the names given by Sir H. Davy to these bodies, than in the places he has assigned them. Aware of the evils of the French nomenclature, founded upon hypothetical views, he has purposely avoided names connected with theory, and has chosen such as may remain unchanged during the perpetual fluctuation of systems. This being the case, we cannot but reprobate the vain spirit of innovation, that invents names without discovering things; and makes distinctions where there are no real differences. Thus, in France, some chemists, in pursuance of their particular views, have thought proper to call the bases of the alkalies metalloids instead of metals, and what is more to be wondered at, these terms have constantly been imported into use by some in our own country. Names to the true philosopher, who looks and examines beyond names, signify but little, but, to the superficial inquirers, who are satisfied with their acquisition, they are of great importance. And those given by discoverers should be held as sacred as the names given by parents to their children, not to be trifled with and altered at every one's capricious taste, but only to be changed when called for by absolute necessity.

A rapid and brilliant course of discovery was the consequence of the decomposition of the fixed alkalies, and the further application of the Voltaic battery to chemical analysis. The alkaline earths had long been suspected to contain metallic matter, and this suspicion was verified by Sir H. Davy, who by various ingenious devices separated their bases from oxygene, and examined them sufficiently to ascertain their metallic nature and some of their physical qualities, and shewed that they approached the common metals in density and fixedness in the fire, though they greatly exceeded them in their affinity for oxygene. The decomposition of the common earths, and the demonstration of the metallic nature of their bases soon followed; but his experiments were not so satisfactory on this subject as