Feb. 5, 1880] 



NATURE 



Some recent very remarkable researches of M. Plante with his 

 rheostatic machine' have shown that fine wires conveying power- 

 ful currents are wrinkled up into well-defined regular nodes, that 

 these effects are accompanied by a peculiar crackling, and that the 

 wire itself becomes brittle, giving clear indication of the vibratory 

 motion of the molecules. He gives as the result of his inquiry 

 that electrical transmission is the result of a series of very rapid 

 vibration of the more or less elastic matter which it traverses, 

 and he points out certain analogies between electric motion and 

 sonorous vibrations. This view is supported by the researches 

 of Professors Ayrton and Perry ■ on the viscosity of dielectrics. 



Prof. Challi>, of Cambridge, has extended this view so far as 

 to embrace magnetism, electricity, light, heat, and gravity in one 

 category of physical force, and to as>ert that they all result from 

 motions and pressures of a uniform elastic fluid medium per- 

 vading all space not occupied by atoms. His views, however, 

 have not received much attention, for they are not based on the 

 foundation of any new facts, and they are utterly subversive of 

 many cherished principles deeply rooted in the scientific mind. 

 It is to be observed, however, that he regards electricity as a 

 form of force. 



Mr. Crookes, in his recent beautiful experimental researches 

 into molecular physics in high vacua, has still more conclusively 

 proved the connection that exists between electrical aciion and 

 molecular motion. In fact, his experiments are so brilliant, his 

 expositions so lucid, that one can fancy one sees with the eye of 

 the body that peculiar play of the molecules which can be 

 evident only to the eye of the mind. Not only has Mr. Crookes 

 established as a physical fact the kinetic theory of gases and the 

 molecular constituti in of matter, but he has indicated the exist- 

 ence of a fourth state of matter where the molecules fly about 

 without mutual let or hindrance. He has also led us to doubt 

 the truth of the generally received opinion that an electric cur- 

 rent flows from the positive to the negative electrode. It would 

 appear from his investigations that the reverse is the case. Be 

 that as it may, he has added one story to the structure of the 

 molecular theory of electricity. 



The criterion of a good theory is, however, its power of pre- 

 diction. A false theory has never led to prevision. Neither the 

 corpuscular theory of light, nor the fluid theories of heat and 

 electricity, ever led to the prediction of something of which eyes 

 had not seen nor ears heard. The triumphs of prediction in 

 astronomy, sr>und, light, and heat are innumerable. Faraday 

 predicted the effect of induction in lowering the velocity of 

 currents of electricity and the action of magnetism on a ray 

 of light. Sir William Thomson predicted that a current in 

 passing from a hot to a cold part of a copper bar would heat 

 the point of contact, while in an iron bar it cools it. Peltier 

 predicted the cooling effect of currents on the junctions of 

 thermoelectric pairs. 



But the true identity of these physical effects is conclusively 

 shown by their quantitative character and by their adhesion to 

 the law of the conservation of energy. Take the case of the 

 electric light : the consumption of coal in a furnace generates 

 steam, the steam works an engine, the engine rotates a coil of 

 wire in a magnetic field, the motion of the coil in this field in- 

 duces currents of electricity in the wire, these currents of elec- 

 tricity produce an arc, and thereby heat and light. The energy 

 of the coal is transformed into heat and light through the inter- 

 mediate agency of electricity. Is it possible to conceive that this 

 intermediate agency is anything but a form of energy? Take 

 the case of the Bell telephone : the energy of the voice produces 

 the energy of sonorous vibration in the air, the vibrations of the 

 air cause the vibrations of the iron disk, the vibrations of the 

 disk vary the magnetism of the magnetic field, this produces 

 currents of electricity in a small coil in this field which vary the 

 magnetism of the distant magnet, which in its turn throws its 

 disk armature into vibration, and thereby repeats at the distant 

 station the sonorous vibrations of the air, and thus reproduces 

 the energy of the voice. A tuning fork comes to rest sooner in 

 front of a telephone than when it is allowed to vibrate freely in 

 air. Here we have the energy of the fork passing through the 

 several stages indicated above, and ultimately coining out in its 

 original form. The energy of sonorous vibrations at the distant 

 station is that lost by the vibrating tuning fork. 



Is it possible to assume that in this cycle of changes energy 

 has been transformed into matter and matter again formed into 

 energy ? It is impossible and absurd. Clerk-Maxwell said — 



1 Comptes Rtttdus, Ixxxix. , pp. 76-80, 1879. 



2 Proc. Roy. Soc pp. 7-8, 1878. 



" When the appearance of one thing is strictly connected with 

 the disappearance of another, so that the amount which exists 

 of the one thing depends on and can be calculated from the 

 amount of the other which has disappeared, -we conclude that the 

 one has been formed at the expense of the other, and that they 

 are both forms of the same thing." 



Would it be possible ta light the streets of New York by the 

 energy of the falling water at Niagara, as has been suggested by 

 our Past President, Dr. Siemens, if the cycle of changes from the 

 one spot to the other were not all different forms of this same 

 energy ? Would it be possible to plough a field a mile away 

 from the source of motive power of the transmitting medium 

 if the electric currents were not forms of the same power? 

 Electricity in its effects is and must be a form of energy. 



The final stage into which any physical theory grows is that 

 in which every action can be expressed in mathematical language, 

 where every phenomenon is calculated upon an absolute physical 

 basis, and where we can foretell exactly what will occur under 

 any possible emergency. This is the present condition of the 

 science of electricity. We can calculate exactly how much 

 steam power is required to generate a given current to produce a 

 given light. We can tell precisely what dimensions of cable are 

 necessary to give a certain number of words per minute on the 

 other side of the globe. Ifa fault develop itself in a long cable 

 through the gastronomic propensities of a thoughtless young 

 teredo, we can calculate to within a few fathoms the locality of 

 his edacious depredation. 



Clerk-Maxwell, ' in his classical work on electricity, has used 

 a somewhat curious argument to show that electricity is not, like 

 heat, a form of energy. He says that energy is produced by the 

 multiplication of " electricity " and "potential," and that it'is 

 impossible that electricity and energy should be quantities of the 

 same category, for electricity is only one of the factors of energy, 

 the other factor being "potential." But this does not militate 

 in any way against the force of the argument, for in nature we 

 can no more do so than we can separate heat and temperature. 

 Energy usually appears as the product of two factors, and it is 

 the equivalent of the work done. Thus, Potential energy is the 

 product of mass and gravitation acting through a distance. 

 Kinetic mergy is the product of mass and the half-square of velo- 

 city. The energy of fluids is the product of volume and pressure. 

 The energy of heat is made up of heat and temperature, and the 

 energy of electricity is the product of electricity and potential. 

 Hence it is that electricity, per se, may be said to be a form of 

 force, while all its effects as known to us are forms of energy. 

 Force alone cannot produce energy ; it must be force and some- 

 thing else. Force is the power of producing energy, and it 

 must have something on which to produce it. Hence matter is 

 always present ; and thus, though heat, light, and electricity are 

 forms of motion, they are in reality properties of matter from 

 which they are inseparable. They are evident to us through the 

 play of the molecules of matter, and thus are properly called 

 molecular forces. 



Earth currents have been a favourite subject of inquiry of 

 mine for many years. I have always entertained the idea that 

 they are directly due to the action of the sun. Some disturbance 

 in the sun cause-, by induction, a variation in the distribution of 

 the lines of potential on the earth's surface, and produces the 

 conditions required for these currents. I have many facts to 

 support this hypothesis, but I want more to confirm it. Profs. 

 Ayrton and Perry have developed a theory of terrestrial mag- 

 netism based on the assumption that the earth is a highly 

 electrified sphere, which not only coincides well with facts, but 

 which tends greatly to support my views. I want observers to 

 record the times of daily maxima and minima. I want them 

 especially to note during those periods of unusual disturbance the 

 direction of the circuits which are not affected, for they would 

 give the direction of the lines of eqni-potential. This not only 

 offers a useful field of observation, but its failure or success will 

 illustrate the modern method of scientific re-earch, when the 

 brain suggests to the hand and the eye w hat they have to do, 

 and what ihey have to look for. 



Mr. Preece then went on to speak of the educational work of 

 the Society and to notice some of the recent practical applications 

 of electricity, and in speaking of the telephone stated that 

 litigation has commenced between the Post-Office and the 

 telephone companies not to restrict or in any way to interfere with 

 the use of the telephone, but to prevent the establishment of a 



1 Vol. i., p. 30. 



