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that the peculiar smell which is evolved when flint, or any siliceous stone gives otrt sparks of fire, is precisely the same to our senses as that which succeeds electrical excitation, or the strong effects of lightning from the atmosphere." "One remark may be tolerated, and not deemed an intrusion on the present occasion; it is this, that this singular identity of smell, stamps silex with such a degree of consequence, as to assimilate it in this quality, at least, with one of the most important objects of nature, the electric fluid of the atmosphere."

I have quoted somewhat at large, and as some may think irrelevantly; but I conceive the subject to be one of deep interest, and that it is treated in a masterly and very argumentative manner. The inquiry into the real nature of the base of oxygen gas is also pending, and Mr. Hume's treatise is on that subject: he, as we have seen, thinks it to be silver, or flint; other authors give no opinion on the subject; but all agree in considering oxygen gas as a peculiar base, saturated with caloric.

I think it will not be hazarding too much, to conjecture that, oxygen gas, as well as hydrogen gas, originates solely in the decomposition of water, in which fluid, its true base is to be found co-existent with the base of hydrogen gas; that they have no other, nor more remote origin; and hence, that all the phenomena, which depend upon the agencies of these two gases may be traced primarily to the decomposition of water, effected by the electrizing principle of the sun's rays, a principle which has been in active operation from a period coeval with that of the sun's existence. Oxygen and hydrogen gases, may then be defined, as two gaseous elastic fluids, derived from water by the operation of solar induction; by which operation, they each receive electricity of a specific nature or modification, the one contrary to that of the other; by the repulsive agency of which specific electricities, each is retained in the gaseous state, till, by the action of some more powerful agency, these gases are induced, either to enter into combination one with the other, or to form electrochemical affinities with other bodies, from which result a vast variety of products, gaseous, fluid, or solid, according to the nature of the several constituents; all of which are of essential importance in the economy of nature.

To define in few words what I mean by natural electricity. I consider it a modification of the sun's light. Light—that is, the solar ray—is poured upon the surface of the globe: extinguished it cannot be,—therefore, it must be absorbed. It may indeed, undergo transmutations; but whether it do, or do not, the solar light is the source and origin of that elementary fire which pervades all matter, and is the grand vivifying principle. While undisturbed, it remains neutral, quiescent, and, as it were, masked; but when excited by chemical action, by friction, ror by percussion, it becomes revealed, or is rendered manifest by its effects. This elementary fire, when revealed in the grander phenomena, is natural electricity. The ingenuity of man has enabled him to call it into activity by his machinery; and then it may be styled artificial electricity; but the prime motor is one and the same.

102. Dates of chemical attraction and repulsion.—In the present imperfect state of our knowledge, chemical science being assuredly but in its infancy, we are scarcely authorized to make use of the terms" law or axiom: however, as some general principles may be of real utility to the student, as tending to fix or give a direction to his ideas, I shall comprise under three heads, those principles, which appear to me as philosophical deductions, either from ascertained facts, or from sound, analogical reasoning. For the first two laws, or principles, I am wholly indebted to the high authority of Sir Humphry Davy: the third is dependant upon the two former; but it is more general and comprehensive in the views which it embraces.

(a.) All bodies which have a chemical affinity for each other are in opposite states of electricity; and chemical affinity depends so much upon electricity, that these natural affinities may be modified or destroyed, by inducing a change in the electrical states, by artificial means.

(b.) Those substances or bodies, which are incapable of chemical combination, are uniformly in the same electrical states: hence, they repel, but cannot attract each other.

(c.) Since bodies which attract one another are possessed of different electricities* and those which repel one another are possessed of the same electricities,—phenomena which are in exact conformity with those of artificial electricity,—it follows that all bodies which attract or repel one another are electrified bodies. When bodies possessing opposite qualities, such as those of acid and alkali, enter into an electro-chemical union, they do it by the attractive or disposing influence of their two electricities; and in this act of union, the two chemical bodies, as well as the two disposing electricities, neutralize each other, and lose their distinctive qualities. And as the union has been induced, and effected by electric attraction, so it is retained by the quiescent attraction of the two electricities, till it is disturbed by a more powerful agency, which may induce the change in the first compound, and give its constituents a tendency to enter into new arrangements. This law will bear upon the whole range of chemical affinities, and hold good in every species of chemical attraction under whatever name or designation it may be known; whether it be that of "simple, compound, disposing, quiescent, or divellent" attraction.

When it is considered, that many substances become electrified by passing from a liquid to a solid state, that electricity is developed by the conversion of water into steam and vapour, by the simple contact of metals, by the sudden rending asunder of pieces of dry wood, (a fact, by the way, that throws light upon the subject of the attraction of cohesion,) by the mere projection of powders upon the cap of an electroscope, and by almost every act of friction, pressure, or percussion, there can remain but little doubt of the universal distribution of this subtile fluid. When, moreover, it is acknowledged by electricians, "that there is every reason to presume that electricity is essentially concerned in the processes that are carried on in the living system, both of animals and vegetables" (every hair, prickle, thorn, or pointed projection of the vegetable body being a most perfect agent of conduction); "when in the animal economy more particularly, the operation of this agent is indicated in the processes of secretion, in the action of the muscles and nerves, and probably, in all the vital functions:" when it begins to be admitted, "that there can be question that electricity is occasionally, if not universally elicited during chemical action," (Treatise, No. 116,) it surely may be allowed me to append the third law, to the two which precede it; and moreover, without incurring a charge of presumption, to assume as a philosophical truth, one which will, in some future day, become an axiom in chemistry, "that, every action of chemical affinity is induced and maintained, by the agency of electrical attraction"

Part III.

WATER CONSIDERED AS ONE OF THE GRAND NATURAL

AGENTS.

103. Decomposition of water by natural agencies.—There are many very striking phenomena, which attend the natural decomposition of this wonderful fluid: I shall endeavour to class and describe them under three separate heads.

(a.) Includes those which are occasioned by solar electric agency, inducing decomposition in the waters superficially deposited on the earth's surface: these, of course, include seas, lakes, rivers, &c. The phenomena which result from this agency, may be chiefly referred to the atmosphere; the consideration of them, therefore, properly belongs to the "Section on the atmosphere" in the succeeding month.

(b.) Includes the phenomena resulting from decomposition effected within the earth's surface, by the electrizing principle of the sun's rays. Among these, the most striking are, (1st.) the developement of the grand volume of the electrical fluid, or elementary fire, distributed over the surface of the globe, the prime source of all the inductions which regulate the electrical states of the atmosphere, and the various mutations of the weather.—(2d.) The separation of tho principle of magnetism.—(3d.) The oxidation of metals; a process which may be considered as the natural and grandest developement of the voltaic electricity; and which, in all probability, includes among its more awful phenomena, earthquakes, and the eruptions of volcanoes.—(4th.) The formation of metallic bodies by the laboration of one of the constituents of water,—hydrogen. This idea is purely hypothetical: it may never be proved to be founded in fact; but as some have advanced the opinion, that the base of hydrogen gas is a metal, I conceive myself fully authorized to invite inquiry into the converse of that opinion. In Sir Humphry Davy's Lecture before the Board of Agriculture, (Agric. Chem., page 180,) we meet with the following observations. "The veins which afford metallic substances are fissures, vertical, or more or less inclined, filled with a material different from the rock in which they exist. This material is almost always crystalline; and usually consists of calcareous spar, fluor spar, quartz, or heavy spar, either separate or together. The metallic substances are generally dispersed through, or confusedly mixed with these crystalline bodies. The veins in hard granite seldom afford much useful metal: but in the veins in soft granite and in gneis, tin, copper, and lead are found. Copper and iron are the only metals usually found in the veins in serpentine. Micaceous schist, sienite, and granular marble are seldom metalliferous rocks. Lead, tin, copper, iron, and many other metals, are found in the veins in chlorite schist. Grauwacke, when it contains few fragments, and exists in large masses, is often a metalliferous rock. The precious metals, likewise iron, lead, and antimony, are found in it; and sometimes it contains veins, or masses of stone coal, or coal free from bitumen. Limestone is the great metalliferous rock of the secondary family; and lead and copper, are the metals usually found in it. No metallic veins have ever been found in shale, chalk, or calcareous sandstone; and they are very rare in basalt and siliceous sand-stone."

If we attentively consider the foregoing passage, we can scarcely

fail to perceive, that metals are chiefly found in veins, the direction of which seems to indicate the disruption of the rocks through which they pass, by the agency of water. The metallic substances are found dispersed among the crystalline bodies, which, it may be remarked, are composed of substances closely allied to that silex that Mr. Hume considered to be identical with oxygen, (see 101.) Mr. Hume may not have established his theory to the very letter; but he has the triumph of finding it now admitted on all hands, that silex contains nearly 50 per cent, of oxygen; and that its base is inflammable, and probably metallic: this base Sir Humphry Davy names silicon. If, then, silex be an oxide of silicon, why may not its base, as well as the oxygen, with which that base is combined, be derived from water? If it be,—then silex—that "multifarious cement," as Mr. Hume styles it—that grand and boundless depository of elementary fire, is neither more nor less than an oxide of hydrogen. No objection can be raised on account of the dissimilarity in point of form and texture; the diamond, the hardest known substance in the world, is a combustible, and may be converted into a gaseous fluid; nor can we conceive it more improbable, that the elements of water should assume the solid form, than that one of them, the hydrogen should in the form of gas, become the lightest of all bodies that possess weight. I would fearlessly hazard the conjecture, that every inflammable body in the creation is either derived from hydrogen alone, or that it contains it, in one of its definite proportions; and, to support the conjecture, I, in the first place, refer to a note at No. 350 of Parkes' Rudiments, p. 176. "The fixed alkalies, which were formerly imagined to be simple substances, are proved by Sir Humphry Davy to be metallic oxides. He has succeeded also in decomposing four alkaline earths; barytes, strontites, lime, and magnesia, the base of which he finds to be metallic substances of the colour of silver. He has likewise announced that he has reason to believe that sulphur and phosphorus are compound bodies, consisting of oxygen, hydrogen, and their peculiar bases." Again, one of the public lecturers, announced that Mr. Faraday of the Royal Institution, discovered, that when potass is acted upon by some of the metals,zinc particularly,—a portion of ammonia was always generated'. The utmost caution was used to secure the

* "The following experiment related among others, by Mr. Faraday, is strongly in favour of the compound nature of azote. An empty tube was filled with hydrogen gas, and zinc foil and a piece of hydrate of potash, were put in it. It is evident that the only elements present were zinc and potassium—with oxygen and hydrogen, forming the water of the hydrate of potash; and yet, on the application of heat, ammonia test evolved, as indicated by moistened turmeric paper, placed in

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