The material nature of electricity has, Mr Editor, been generally admitted. The great difficulty in the subject seemed to arise from a doubt whether one or two fluids were concerned in its phenomena. But the simplifying doctrines of the present age have taught us to dispense with all unnecessary agents, to attribute a diminished temperature, not to the radiation of cold, but to the absence of heat; night, to the rays of the sun, not, as was believed by some philosophers in the days of Bacon, to the influence of certain tenebriferous stars that radiated darkness; and the two electrical states, not to the contention of two rival powers, but to the excess or deficiency of a single fluid. Yet we have no more proof of the materiality of electricity than of that of heat or light; and the circumstance of its production, or as it is commonly called excitation, by the contact or friction of certain substances, appears rather to militate against this opinion. A body positive renders that in its immediate vicinity negative; the next to that is again positive, and its neighbour negative; thus forming, seemingly thro’ the whole globe, a chain of alternate links. Conductors, that is bodies that readily transmit electricity, have only two poles, one positive and the other negative, while in non-conducting bodies each separate particle has its own poles. Supposing a body positive to be in some peculiar state of action, it is strange that that action should produce a corresponding rest on the part of an adjacent body, and that this rest should in its turn induce action in its vicinity. But if electricity be a fluid, universally diffused, partaking of the properties of heat and light, and whose particles are repulsive to each other, the question does not appear difficult. This power of repulsion, we find, under the name of a tendency to universal diffusion, in all the gases. It is this law, which, notwithstanding the difference of weight in the various aeriform bodies that mingle in out atmosphere, preserves its composition always uniform; and provides, that in the crowded city or the extended plain, on the tops of mountains or in the depths of valleys (whatever be the adventitious and unknown circumstances that give contagion or salubrity to the air, and whether it be dense or rarified) the proportions of oxygen and of its other elements are always the same. If the particles of electricity be repulsive to each other, that is in other words if they have a tendency to universal diffusion, or to preserve universal equilibrium, it is not strange that in ordinary circumstances there should be some space between them. Bodies capable of exciting electricity are those incapable of conducting, that is of partaking with it. Thus when a piece of glass and one of silk are rubbed together in the common electrical machine, the brass conductor receives from the silk the portions of electricity separately imprisoned in each of its particles, which waiting like small globules of mercury, are ready to escape at once to the first object that presents itself to receive them. The analogy between heat and electricity is so great, and their effects so much influenced by each other, that it is difficult not to consider them as modification of the same fluid. Heat excites and makes great difference in the electrical state of bodies, and electricity in return produces at times all the phenomena of the most violent heat. The fusion and deflagration of metals, indeed most of the effects of the Voltaic Battery, may be produced by the operation of fire; and indeed, to quote the words of an eminent professor, “the greatest heat which science has yet taught us to attain is by means of the Voltaic Battery.”
Heat, light, and electricity are in all probability material; they may be three independent fluids, or one may be formed by the union of the two others. In this case I should be inclined to think electricity the offspring of heat and light combined: these bodies may exist separately in the sun-beam, as oxygen and hydrogen in the atmosphere, and may unite as they combine to form water. If again the quantity of these two substances received daily from the sun be mentioned as an objection, I must again call to remembrance the mutual radiation of all bodies upon earth, and of the planets to each other and even to the sun. Water is continually rising in vapour from the sea, the earth, the leaves of trees, and the bodies of animals, but it returns in the form of dew or of rain, and the tribute poured into the ocean by its countless streams is repaid by the clouds that break upon their parent mountains.
If heat, light and electricity be merely actions, let it be remembered that there is still a want of some cause to soothe them into rest or instigate their exertions; and that it was soon found that the physiologists who, to explain the action of the muscles, supposed them occasioned by electricity, were only a step farther from their object: it was as easy to suppose a cause at once to move the muscles, as one to influence the electricity to put them in motion.
I am, dear Sir,
Your most obedient