Electricity

The law of electrical attraction and repulsion has been determined by suspending a needle of gum-lac horizontally by a silk fibre, the needle carrying at one end a piece of electrified gold leaf. A globe in the same or opposite electrical state when presented to the gold leaf will repel or attract it, and will therefore cause the needle to vibrate more or less rapidly according to the distance of the globe. A comparison of the number of oscillations performed in a given time at different distances will determine the law of the variation of the electrical intensity, in the same manner that the force of gravitation is measured by the oscillations of the pendulum. Coulomb invented an instrument which balances the forces in question by the force of the torsion of a thread, which consequently measures the intensity; and Sir William Snow Harris has constructed an instrument with which he has measured the intensity of the electrical force in terms of the weight requisite to balance it. By these methods it has been found that the intensity of electrical attraction and repulsion varies inversely as the square of the distance. However, the law of repulsive force is liable to great disturbances from inductive action, which Sir William Snow Harris has found to exist not only between a charged and neutral body, but also between bodies similarly charged; and that, in the latter case, the inductive process may be indefinitely modified by the various circumstances of the quantity and intensity of the electricity and the distance between the charged bodies.

The quantity of electricity bodies are capable of receiving does not follow the proportion of their bulk, but depends principally upon the form and extent of their surface. It appears from the experiments of Sir W. S. Harris that a given quantity of electricity, divided between two perfectly equal and similar bodies, exerts upon external bodies only one fourth of the attractive force apparent when disposed upon one of them; and if it be distributed among three equal and similar bodies, the force is one ninth of that apparent when it is disposed on one of them. Hence, if the quantity of electricity be the same, the force varies inversely as the square of the surface on which it is disposed; and if the surface be the same, the force varies directly as the square of the quantity of electricity. These laws however do not hold when the form of the surface is changed. A given quantity of electricity disposed on a given surface has the greatest intensity when the surface has a circular form, and the least intensity when the surface is expanded into an indefinite straight line. The decrease of intensity seems to arise from some peculiar arrangement of the electricity depending on the extension of the surface. It is quite independent of the extent of the edge, the area being the same; for Sir W. S. Harris found that the electrical intensity of a charged sphere is the same with that of a plane circular area of the same superficial extent, and that of a charged cylinder the same as if it were cut open and expanded into a plane surface.

Electricity may be accumulated to a great extent in insulated bodies, and so long as it is quiescent it occasions no sensible change in their properties. When restrained by the non-conducting power of the atmosphere, its tension or the pressure it exerts is proportional to the coercive force of the air. If the pressure be less than the coercive force, the electricity is retained; but the instant it exceeds that force in any one point it escapes, and that more readily when the air is attenuated or saturated with moisture, for the resistance of the air is proportional to the square of its density, but the inductive action of electricity on distant bodies is independent of atmospheric pressure. The power of retaining electricity depends also on the shape of the charged body. It is most easily retained by a sphere, next to that by a spheroid, but it readily escapes from a point, and a pointed object receives it with most facility. The heat produced by the electric shock is proportional to the square of the quantity of electricity discharged, and is so intense that it fuses metals and volatilizes substances, but its intensity is not felt to its full extent on account of the shortness of its duration. It is only accompanied by light when the electricity is obstructed in its passage through substance.

The earth possesses a powerful electrical tension, and the atmosphere when clear is almost always positively electric. Its electricity is stronger in winter than in summer, during the day than in the night. The intensity increases for two or three hours from the time of sunrise, comes to a maximum between seven and eight, then decreases towards the middle of the day, arrives at its minimum between one and two, and again augments as the sun declines till about the time of sunset, after which it diminishes and continues feeble during the night. The mere condensation of vapour is a source of atmospheric electricity; but although it is also produced by the vapour that rises from the surface of the earth, it is not under all circumstances. M. Pouillet found that electricity is only developed when accompanied by chemical action: for example, when the water whence the vapour proceeds contains lime, chalk, or any solid alkali, negative electricity is produced; and when it holds in solution either gas, acid, or some of the salts, the vapour is positively electric.

The actual quantity of electricity in any part of a cloud is extremely small. The intensity of the flash arises from the great extent of surface over which it is spread, so that clouds may be compared to enormous Leyden jars thinly coated with electricity, which only acquires its intensity by its instantaneous condensation. The rapid and irregular motions of thunder clouds are probably more owing to strong electrical attractions and repulsions among themselves than to currents of air, though both are no doubt concerned in these hostile movements. The atmosphere becomes intensely electric on the approach of rain, hail, snow, sleet, and wind; but it varies afterwards, and the transitions are very rapid on the approach of a thunderstorm.

When the air is rarefied by heat, its coercive power is diminished, so that the electricity escapes from the clouds in those lambent diffuse flashes without thunder so frequent in warm summer evenings; and when the atmosphere is highly charged with electricity, it not unfrequently happens that electric light, in the form of a star, is seen on the topmasts and yard-arms of ships. In 1831 the French officers at Algiers were surprised to see brushes of light on the heads of their comrades, and at the points of their fingers when they held up their hands. This phenomenon was well known to the ancients, who reckoned it a lucky omen.

Observe now what we have been doing. Turning to the general question, let us note where these successive interpretations have carried us. We began with quite special and concrete facts. In explaining each, and afterwards explaining the more general facts of which they are instances, we have got down to certain highly general facts:—to a geometrical principle or property of space, to a simple law of mechanical action, to a law of fluid equilibrium—to truths in physics, in chemistry, in thermology, in electricity. The particular phenomena with which we set out, have been merged in larger and larger groups of phenomena; and as they have been so merged, we have arrived at solutions that we consider profound in proportion as this process has been carried far. Still deeper explanations are simply further steps in the same direction. When, for instance, it is asked why the law of action of the lever is what it is, or why fluid equilibrium and fluid motion exhibit the relations which they do, the answer furnished by mathematicians consists in the disclosure of the principle of virtual velocities—a principle holding true alike in fluids and solids—a principle under which the others are comprehended. And similarly, the insight obtained into the phenomena of chemical combination, heat, electricity, &c., implies that a rationale of them, when found, will be the exposition of some highly general fact respecting the constitution of matter, of which chemical, electrical, and thermal facts, are merely different manifestations.

man of science attributes certain facts of na- ture to what he calls the influence of gravi- tation, he has or should have no intention to intimate that there is any such thing in na- ture, any such substance or entity, as gravi- tation. The word marks a mere mental gen- eralization on our part of certain widely diffused and various facts of experience, the generalization itself being only an instinctive effort of the common or associate mind of the race to indue itself, by the instrumental- ity of the individual mind, with that perfect scientific form or order which shall constitute its own eventual and permanent self-conscious- ness. All these generalizations of our natu- ral experience are only so many approxima- tions, on the part of the common mind of the race, to the recognition of its own univer- sality and unity. Nature is but the spiritual man turned inside out, or the contents of his otherwise unknown and unimaginable spiritual personality revealed to his senses. It is not a substance, but the shadow of a substance whose reality is altogether spiritual. Yet when you see the energy with which our so-called philosophers pursue cause to its last fastness, and seek to waylay heat and take light cap- tive in the web of their cunning devices, or bleat forth idle prayers to know what after all is electricity and what magnetism, you must inevitably infer that the living and unitary sub- stance they seek under all these shifting forms, the absolute personality they demand under ail

90 A few years ago one of the strongest arguements for the theory that the hemispheres are purely supernumerary was Soltmann’s often-quoted observation that in new-born puppies the motor zone of the cortex is not excitable by electricity and only becomes so in the course of a fortnight, presumably after the experiences of the lower centres have educated it to motor duties. Paneth’s later observations, however, seem to show that Soltmann may have been misled through overnarcotizing his victims (Pflüger’s Archiv, vol. 37, p. 202). In the Neurologisches Centralblatt for 1889, p. 513, Bechterw returns to the subject on Soltmann’s side without however, noticing Paneth’s work.

I am sure that this concrete and total manner of regarding the mind’s changes is the only true manner, difficult as it may be to carry it out in detail. If anything seems obscure about it, it will grow clearer as we advance. Meanwhile, if it be true, it is certainly also true that no two ‘ideas’ are ever exactly the same, which is the proposition we started to prove. The proposition is more important theoretically than it at first sight seems. For it makes it already impossible for us to follow obediently in the footprints of either the Lockian or the Herbartian school, schools which have had almost unlimited influence in Germany and among ourselves. No doubt it is often convenient to formulate the mental facts in an atomistic sort of way, aud to treat the higher states of consciousness as if they were all built out of unchanging simple ideas. It is convenient often to treat curves as if they were composed of small straight lines, and electricity and nerve-force as if they were fluids. But in the one case as in the other we must never forget that we are talking symbolically, and that there is nothing in nature to answer to our words. A permanently existing ‘idea’ or ‘Vorstellung’ which makes its appearance before the footlights of consciousness at periodical intervals, is as mythological an entity as the Jack of Spades.