John Tyndall

“ Space must here be an insulator, for if it were a conductor it would resemble a 'fine metallic web' penetrating the lac in every direction. But the fact is that it resembles the wax of black sealing wax, which surrounds and insulates the particles of conducting carbon, to which the blackness is due. In the case of shellac, therefore, space is an insulator. But in the case of a conductor we have, as before, space surrounding every atom. If space be an insulator, as proved a moment ago, there can be no transmission of electricity from atom to atom. ”

“ In relation to this subject, Faraday repeatedly quotes the memorable words of Newton: 'That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, and without the mediation of anything else, by and through which this action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking will ever fall into it. ”

“ Barlow and Christie had experimented on iron shells and iron disks, but Faraday, with a brass globe and a copper disk, obtained all their effects. They had their eye upon the metal as capable of magnetism; he had his eye upon it as a conductor of electricity. His speculations and experiments on the possible action of the earth when water, whether tidal or fluvial, flowed over its surface, are deeply interesting. ”

“ His experiments and speculations in the deportment of crystals in the magnetic field, a deportment predicted by Poisson, and discovered experimentally by the illustrious geometrician Plucker, are profoundly interesting and instructive. They throw more light than any others on the character of Faraday's mind and culture. ”

“ But if electric induction be transmitted as he supposed, by contiguous particles, is it not probable that the particles of different bodies will exhibit different powers of transmission? He set to work to test this idea, and ended by the discovery of that quality of 'di-electrics' which in submarine cables now plays so important a part, and which retains the name that Faraday gave it. By suitable devices he placed a small metal sphere in the middle of a larger hollow one, leaving a space of somewhat more than half on inch between them. ”

“ Every well-known experimenter is sure to be flooded with proposals and suggestions from outsiders. Crowds of such proposals came to Faraday, but one of them only, he declared, bore the slightest fruit. A young man named William Jenkin had observed a shock and spark of a peculiar character on the interruption of a voltaic current passing through a circuit containing a helix. ”

“ Whether in these inquiries Faraday succeeded in establishing the points at which he aimed is more than can be asserted, but that a body so magnetic as oxygen, swathing the earth, and subject to local variations of temperature, diurnal and annual must influence the manifestations of terrestrial magnetism can hardly be doubted. The air that stands on a square foot of the earth's surface is equivalent in magnetic force to 8,160 pounds of crystallised protosulphate of iron. Such an envelope can hardly be absolutely neutral as regards the deportment of the magnetic needle. ”

“ Oxides, chlorides, iodides, and sulphides were proved to be insulators when solid, and conductors when fused; the passage of the current through the fused mass being always accompanied by decomposition. Whether any trace of electricity could pass through a compound liquid without decomposing it was a disputed point. Faraday leaned to the idea that a small quantity might do so. Other investigators, foremost among whom was the celebrated De La Rive, contended that no trace of electricity can pass through a liquid compound without producing its equivalent decomposition. ”

“ Here the vibrating atom must be regarded as the real source of the motion. Still Faraday's reasonings are in the highest degree curious and ingenious. Grappling with the notion that matter is made up of molecules separated from each other by intermolecular spaces, he observes that 'space must be taken as the only continuous part of a body so constituted.' He turns to electricity in search of a test for this notion. ”

“ It is an interesting experiment to place a lighted candle between two pointed poles to split the flame in two by the of the magnet. According to the position of the flame it can be depressed, elevated, or blown aside, by the magnetic force. Faraday repeated Bancalari's experiments, and, passing from flames to gases generally, established their magnetic and diamagnetic powers. He made numerous experiments with oxygen and nitrogen, which, as constituents of the earth's atmosphere, had an importance of their own. ”

“ Dulong and Thénard proved afterwards that a well-cleansed platinum wire could be raised to incandescence by its action on a jet of cold hydrogen. Faraday found this power of provoking combination to be possessed in a striking degree by the positive platinum plate of his decomposing cell. The purification of the platinum by the oxygen discharged against it was the cause of its activity.
'In our conceptions and reasonings regarding the forces of nature we perpetually make use of symbols which, when they possess a high representative value, we dignify with the name of theories. ”

“ At that time the 'magnetism of rotation' excited universal attention. A non-magnetic metallic disk placed beneath a magnetic needle and set in rotation drew the needle after it. On reversing the motion of the disk the needle first stopped and then turned backwards, following the new rotation. Arago was the discoverer of this action, but he ventured on no explanation of it. Its solution was reserved for Faraday. The disk being a conductor of electricity, he clearly saw that his newly discovered induced currents must be excited in it by the adjacent needle. ”

“ Faraday next showed that the mere approach of a wire forming a closed curve to another wire through which a current was flowing, aroused in the former an induced current. The withdrawal of the wire also excited a current in the opposite direction. These currents existed only during the time of approach and withdrawal, and vanished when the motion ceased. Prior to these experiments magnetism had been evoked by electricity. He now aimed at exciting electricity by magnetism. Round a welded iron ring he wound two coils of insulated copper wire, the coils occupying opposite halves of the ring. ”

“ The deportment of oxygen in air 'was very impressive, the bubble being pulled inward, or towards the axial line, sharply and suddenly, as if the oxygen were highly magnetic.' A strong vein of metaphysics runs through the speculations of Faraday, but his experiments are always handled with regal power. He thought it important to fix the magnetic zero, to discover if possible a substance neutral to the magnet when excited to its uttermost. ”

“ Such conceptions have their advantages and their disadvantages; they afford peaceful lodging to the intellect for a time, but they also circumscribe it, and by-and-by, when the mind has grown too large for its lodging, it often finds difficulty in breaking down the walls of what has become its prison instead of its home,' These words are quoted because they so chime in with Faraday's views, that when he heard them he could not repress a warm expression of assent. ”

“ A strong imagination is required to understand him and to sympathise with him. His views had to him almost the stimulus of a religion, and they urged him to work with expectation and success in regions where a less original, though better trained, man of science would have laid down his tools in despair.
His 'lines of magnetic force' took possession more and more of Faraday's mind. The last three papers of his experimental researches are occupied with this subject. In these papers experiments of exquisite beauty, on wires moving round magnets, are described. ”

“ Nearer than anybody known to the writer, he came to the fulfilment of the precept, 'Take no thought for the morrow.' He had absolute confidence that, in case of need, the Lord would provide. A man with such feeling and such faith was naturally heedless of laying by for the future. ”

“ With the electrolysis of water, as measured by his voltameter, he compared the electrolysis of other substances, both singly and in series, and proved beyond doubt that the decompositions of the voltaic battery are as definite in their character as those chemical combinations which gave birth to the atomic theory. ”

“ Suspended before either pole of an electro-magnet it was repelled when the force was developed. Suspended as a bar between the two poles, it retreated when the magnet was excited, setting its length at right angles to the line joining the poles. A magnetic bar, similarly suspended, always set its length from pole to pole. The first of these positions Faraday called the 'equatorial' position, the second the 'axial' position. In accordance with his usual habit he pushed his experiments on diamagnetism in all possible directions. ”

“ For the word 'poles,' previously applied to the plates plunged in a decomposition cell, he substituted the word 'electrodes.' The decomposing liquid he called an 'electrolyte.' and the act of decomposition 'electrolysis.' These terms are now of everyday use in science. The term 'anode 'for the positive electrode and 'cathode 'for the negative one, are less frequently used, while the terms 'anion' and 'cation,' names given to the respective constituents of the decomposed electrolyte, and the term 'ion,' including both anions and cations, are hardly used at all. ”

“ He heard lectures from Mr. Tatum on natural philosophy at 52 Dorset Street, Fleet Street, the cost being a shilling a lecture. He read much, and was specially indebted to Mrs. Marcet's 'Conversations in Chemistry.' Mr. Dance, a member of the Royal Institution, was a customer of Riebau's, and Faraday had impressed him so favourably, that he gave the youth tickets for the last four lectures delivered by Davy in the Royal Institution. ”

“ After a year's trial, being then thirteen, he was bound apprentice to Riebau. The boy's conduct had been so exemplary that he was taken without fee. This was in 1804, Riebau's establishment was in Blandford Street, Manchester Square. ”