and Faraday died believing in the probable unity of forces, and that the establishment of the fact awaits the age, as a glorious discovery in natural knowledge.1

Materialism has essayed to explain the mysterious connection of mind with matter, and to include what it has styled thought-force in the category of related forces, but in so doing has passed beyond the limits of physical science and trenched upon ground where finite faculties are powerless. The apt words of Pres. Barnard seem conclusive here. "Thought cannot be a physical force, because thought admits of no measure.'

Out of the doctrine of correlation, as a logical consequence, springs that of the conservation of force. Like its antecedent theory it is not without its difficulties, its failing cases. Generally accepted, it is not yet absolutely verified, but is regarded as standing on a firmer basis than did the Newtonian theory of gravitation, till Laplace, after a century from its origin, completed and made it a law by adapting to it all celestial phenomena. When the theory of conservation shall be fully established, we shall have arrived at the marvellous conclusion, that finite agencies can no more create force than they can create matter, and that force is as indestructible as matter. Or,-stated in another form,-the sum of the forces which are in operation in the universe, like the amount of matter, is constant and invariable.

No other theory, save that of gravitation, can show such a record of results as this which the atomic theory exhibits. Can that which has been so fertile in splendid generalizations, and which seems to to bear within itself the germ of indefinite progress, be superseded and cast aside? It may be, and at no distant day. A great revolution in chemistry has long appeared to be just at hand. Ever since Davy proved the before supposed simple earths and alkalies to be compound by discovering their metallic bases, it has been suspected, to use his own words, that "Matter may ultimately be found to be the same in essence, differing only in the arrangement of its particles; or two or three simple substances may produce all the varieties of compound bodies." And such have been the uniform indications and tendencies of science, from Davy's day to ours, that no chemist would be surprised to learn to-morrow that any one of our sixty-three so-called elements has been decomposed.

1 Life and Letters, II, p. 385.

2 Address before Am. Assoc. for Adv. Sci., Aug. 1868.

3 On this point see Prof. J. P. Cooke, Religion and Chemistry, p. 331.

Davy's Chemical Philosophy, American edition, 1812, p. 101.

One of the most striking of these indications is afforded by diamond, plumbago and charcoal. No substances known exhibit more strongly marked and more distinct properties than these three. Yet analysis can tell us nothing more of them than this, that they are three different modifications of one and the same element, carbon. This existence of the same substance in different states, each marked by peculiar properties, we call allotropism; and though the theory under review accounts for the paradox by saying that the atoms of diamond, plumbago and charcoal are grouped in three several ways, and hence the difference of characters, the fact probably is that here analysis fails, that there is something which it does not reach. This and like cases create a strong presumption that our present elements have a composite structure. A new instrument, or the new application of an old one, may be all that is wanting to convert presumption into demonstration. "Spectrum analysis," says the American chemist already quoted, "although yet in its infancy, promises to be one of the most powerful instruments of investigation ever applied in physical science. It seems to be the key which will in time open to our view the molecular structure of matter." The spectroscope, then, may resolve the elements; but if not, another and more potent agent may be soon forthcoming.

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The revolution that must follow such a discovery would undoubtedly be most radical. The whole aspect of chemistry and its related sciences would be changed. Some of the probable consequences can be be foreseen, but others would follow of which, prior to the event, we cannot even conjecture. In 1830, the controversy between Cuvier and Saint Hilaire, champions respectively of special teleology and general homology (unity of plan), as respects the vertebrate skeleton, culminated in a "public explosion," which the poet Goethe proclaimed to be "a far more important event than the French revolution, which was ringing that same year in the ears of Europe." But compared with the catastrophe that this one discovery in chemistry might inaugurate, it is safe to say that any one, perhaps all past scientific revolutions together, might be but as the tempest that wastes a neighborhood to the cataclysm that should devastate a continent. Some of its non-scientific consequences might be sufficiently startling. When gold and silver shall be shown to be composite, the chemist may be able to manufacture them from their elements. The standard of values gone, where would commerce, wealth, finance, and the social structure, find footing, amid the general deluge?

1 Prof. J. P. Cooke, Chemical Philosophy, p. 190.

2 Quoted by McCosh, Typical Forms, Carters' edition, New York, p. 175.

The atomic theory would probably go to wreck in such a storm as this. If not, it would survive only by virtue of its anchorage on the unknown and unknowable. Should a substance more attenuated than hydrogen be discovered, the elastic theory might perhaps adapt itself to new exigencies by splitting the old atom. It can never be proved nor actually disproved, unless the ultimate structure of matter shall be revealed to us. But though the attainment of this knowledge is as inconceivable as ever, the results of spectrum analysis already reached suggest speculations on this point that are most interesting, and that may prove to be very rich in theoretical fruit. In that post-diluvian day to which we have looked forward, speculation may supply some new hypothetical basis for chemistry, more in accordance with facts as they shall then appear; or, quite as probably, under the new order of things some central fact, like that of gravitation in astronomy, will furnish a solid foundation upon which the science may build up a great fundamental law, independent of baseless hypothesis.

But should the looked-for revolution never come, the fate of the atomic theory may be none the less certain. We have spoken of it as still the trunk of chemistry. But if we look again, we shall find on nearer inspection, that this trunk, which in the distance passes for a solid body, is in fact nothing more than a hollow shell.

The existence of atoms is confessedly improbable; and it has long been conceded by the ablest minds that, considered as minute solid bodies from which emanate the attractions and repulsions that have been regarded as giving to matter its properties, they could serve no purpose whatever. Different devices have been adopted to escape the difficulties every definition of the atom has involved. Of late it has been held that the true chemical idea of the atom is more nearly represented by the corresponding Latin word individuum, and that it is the "chemical individual, the unit, in which the mind seeks to repose for the time the individuality of that as yet undivided substance we call an element." But as even this definition implies the extreme minuteness of the atom, how shall we answer the question proposed by the eminent physicist, Sir Wm. Thompson, in a recent number of "Nature?" 2 "If atoms are inconceivably small, why are not all chemical actions infinitely swift?" He himself replies, that retaining its fundamental assumptions, "chemistry is powerless to deal with this and many other questions of paramount importance." If these and many other objections against the atomic theory that might be cited are valid, it would seem to be already a failure. But

1 Cooke, Chemical Philosophy, p. 70. 2 No. 22, March 31, 1870.

B

when it dies, all the names that have grown up with it, and all the ideas, speculations and generalizations that are based upon it, must also pass away, and the vacuum it will leave must be immense.

Within the limits of chemistry proper, materialism has gathered none but the most perishable fruit. The power, wisdom and goodness of God are so clearly inscribed on the chemical elements and in the wonderful laws of their combination, wherein regard to the ideas of number, symmetry and proportion is as manifest as in any work of human art, that unbelief has found nothing here from which it. could distil poison effectual for its purposes. Many attempts have been made, but all have ended in signal failure.

But the application of the atomic theory to physics has yielded to skepticism abundant material. The dynamic theory of force, as the motion of atoms, has been a favorite, and perhaps the strongest prop of the materialism of our day. Over this idea unbelief has fairly run riot. Witness the frantic efforts to extend the doctrine of correlation till thought and will become only results of molecular change in the brain, and the triumphant heralding of all this as proved, when it has not even been shown to be probable. Indeed, Mr. Wallace, one of the authors of the Darwinian theory, himself declares that in making such an assertion, "a great leap in the dark has been taken from the known to the unknown."

Now the decay of the atomic theory is more and more surely turning the minds of men to the necessity of spiritual views of force. Here, and we believe elsewhere, the real tendency of modern science is not towards, but from materialism. Atoms gone, what becomes. of the dynamic theory. For though the facts, so far as they are established, of correlation and conservation remain intact, whatever be the nature of force, the explanation of forces as modes of motion is no more. What do we know of the essence of force; or what can we ever know of it, with the aid of any possible scientific theory? Dr. Oliver Wendell Holmes says, in his "Border Lines of Knowledge in Medical Science:"2 "Force does not admit of explanation, nor of proper definition, any more than the hypothetical substratum of matter." We know the fact of gravitation, but, like our fathers, nothing of its cause. Admitting for a moment that every force is resolvable into motion as its element, how shall we account for the motion? The only cases of motion that we are at all competent to deal with, are those in which we ourselves bear part. And even here all we can say is, that our will, through the medium of muscular contractility

1 Contributions to the Theory of Natural Selection, p. 366. 2 P. 15.

is, in some unexplained way, the cause of the motions we voluntarily put forth. But, whether forces are modes of motion or not, every current of science, whithersoever its set may appear to be, is drifting steadily upon one inevitable conclusion. Granting, if any one desires it, that, as is highly probable but not actually proved, muscular force is only the transformed energy derived from the primary forces of nature, what is the power that touches the spring and converts the potential energy of the muscle,—or of the carbon in it, if you please, -into the actual energy of motion? That power is will; and having traced back one force to an origin in our own will, while we have no knowledge of any other primary cause of force, are we not led almost irresistibly to believe that all the forces of nature are but efforts of the one Supreme will? Who can fear the result, when this, the spiritual and Christian theory of force, shall be tested side by side with any possible mechanical or material one? And shall we not then say with Dr. Holmes1: "Force is the act of immanent divinity. That is all I know. There is no bridge my mind can throw from the 'immaterial' cause to the 'material' effect. . . . For me it is the Deity himself in action." And like in substance is Sir John. Herschel's declaration, that "it is but reasonable to regard the force of gravitation as the direct or indirect result of a consciousness or will existing somewhere."

Passing now to geology, what is the state of theory in this important science? If any one theory may be said to be the basis of systematic geology it must be this, that, "Identity of fossils proves identity of age of strata." If this be disproved, the foundation is gone for the geology of the fossiliferous rocks, as now held,—that part of the science which is the chief one, and whose classifications and names are popularly supposed to represent facts so substantial that to question them is the highest presumption. Yet, if certain objections brought against this theory are real, then a worse thing happens to geology than has occurred to the atomic theory. The cloud on which chemistry has been always admitted to rest, is merely dissolving from sight; but the disaster to geology comes, if it is to come, from the failure of a groundwork of supposed facts.

The source of peril to geology is a very simple one. Some thirtyfive years since, Edward Forbes converted the oysterman's dredge into an instrument of zoological research. This insignificant scraper has for thirty years been steadily undermining geological theory, and

1 Op. cit., p. 16.