[79] 915.
[80] 917.
[81] 855.
Thus the great principle of the identity of electrical and chemical action was completely established. It was, as Faraday with great candor says,[82] a confirmation of the general views put forth by Davy, in 1806, and might be expressed in his terms, that “chemical and electrical attractions are produced by the same cause;” but it is easy to see that neither was the full import of these expressions understood nor were the quantities to which they refer conceived as measurable quantities, nor was the assertion anything but a sagacious conjecture, till Faraday gave the interpretation, measure, and proof, of which we have spoken. The evidence of the incompleteness of the views of his predecessor we have [already] adduced, in speaking of his vague and [301] inconsistent theoretical account of decomposition. The confirmation of Davy’s discoveries by Faraday is of the nature of Newton’s confirmation of the views of Borelli and Hooke respecting gravity, or like Young’s confirmation of the undulatory theory of Huyghens.
[82] 965.
We must not omit to repeat here the moral which we wish to draw from all great discoveries, that they depend upon the combination of exact facts with clear ideas. The former of these conditions is easily illustrated in the case of Davy and Faraday, both admirable and delicate experimenters. Davy’s rapidity and resource in experimenting were extraordinary,[83] and extreme elegance and ingenuity distinguish almost every process of Faraday. He had published, in 1829, a work on Chemical Manipulation, in which directions are given for performing in the neatest manner all chemical processes. Manipulation, as he there truly says, is to the chemist like the external senses to the mind;[84] and without the supply of fit materials which such senses only can give, the mind can acquire no real knowledge.
[83] Paris, i. 145.
[84] Pref. p. ii.
But still the operations of the mind as well as the information of the senses, ideas as well as facts, are requisite for the attainment of any knowledge; and all great steps in science require a peculiar distinctness and vividness of thought in the discoverer. This it is difficult to exemplify in any better way than by the discoveries themselves. Both Davy and Faraday possessed this vividness of mind; and it was a consequence of this endowment, that Davy’s lectures upon chemistry, and Faraday’s upon almost any subject of physical philosophy, were of the most brilliant and captivating character. In discovering the nature of voltaic action, the essential intellectual requisite was to have a distinct conception of that which Faraday expressed by the remarkable phrase,[85] “an axis of power having equal and opposite forces;” and the distinctness of this idea in Faraday’s mind shines forth in every part of his writings. Thus he says, the force which determines the decomposition of a body is in the body, not in the poles.[86] But for the most part he can of course only convey this fundamental idea by illustrations. Thus[87] he represents the voltaic circuit by a double circle, studded with the elements of the circuit, and shows how the anïons travel round it in one direction, and the cathïons in the opposite. He considers[88] the powers at the two places of action as balancing against each other through the medium of the conductors, in a manner [302] analogous to that in which mechanical forces are balanced against each other by the intervention of the lever. It is impossible to him[89] to resist the idea, that the voltaic current must be preceded by a state of tension in its interrupted condition, which is relieved when the circuit is completed. He appears to possess the idea of this kind of force with the same eminent distinctness with which Archimedes in the ancient, and Stevinus in the modern history of science, possessed the idea of pressure, and were thus able to found the science of mechanics.[90] And when he cannot obtain these distinct modes of conception, he is dissatisfied, and conscious of defect. Thus in the relation between magnetism and electricity,[91] “there appears to be a link in the chain of effects, a wheel in the physical mechanism of the action, as yet unrecognized.” All this variety of expression shows how deeply seated is the thought. This conception of Chemical Affinity as a peculiar influence of force, which, acting in opposite directions, combines and resolves bodies;—which may be liberated and thrown into the form of a voltaic current, and thus be transferred to remote points, and applied in various ways; is essential to the understanding, as it was to the making, of these discoveries.
[85] Art. 517.