of 2.3 volts per element. The charge at a constant current requires from 8 to 10 hours, with a difference of potential amounting to 2.5 volts per element at the end of the charge. The shunt dynamos generally used for industrial purposes being calculated to furnish a constant difference of potential rather than a constant intensity, are well adapted to the system of charging advocated by M. Picou, and it is probable that his paper will have the practical result of causing the statement of the rate of charge to disappear from the catalogues of makers of accumulators, the statement of the potential of charge being substituted for it with much greater advantage.

ELECTRICITY, ETHER, AND MATTER.

BY J. GRAY, B.Sc.

WITHIN the last few years the development of electrical theory has been so rapid that many electricians have been unable to keep pace with it. Some of those who have taken the trouble to make themselves acquainted with the modern views, still have considerable doubt as to whether they are right in abandoning their old faith; while others have unhesitatingly pronounced the conclusions of the modern theorists to be "a product of the imagination." Mr. J. T. Sprague, in the pages of the Electrician, and of the English Mechanic, and Mr. S. A. Varley in the ELECTRICAL REVIEW, have recently been attacking, with their well known ability, the theories of Maxwell and his school. If the discussion which has resulted does not finally settle the questions in dispute, it will do important service in ventilating the subject and eliminating fallacies perhaps from both sides.

Maxwell, as is well known, considered that the medium which transmits electrical energy was identical with that which transmits light. This medium-the so-called luminiferous ether-it is now generally admitted, must be something different from Matter, using for convenience the term Matter to comprise only the elements of the chemist. The evidence for the existence of the luminiferous ether, rests on the necessity for having in interstellar space, where sufficient Matter does not exist, a medium which has sufficient mass and rigidity to transmit the energy of light. The amount of energy produced per minute by direct sunlight falling on a square centimetre has been measured by Pouillet. From this, by dividing by the velocity of light the quantity of energy in a cubic centimetre can be calculated. By the law of inverse squares, the energy per unit volume near the sun, is found to be 1886 ergs. According to the undulatory theory of light, this energy is in the form of wave motion, and if we assume with Sir W. Thomson that the amplitude of a wave is not more than oth part of the wave length, the coefficient of rigidity, and the density of the ether can be easily calculated. The coefficient of rigidity comes out to be 842-8, and the density 9-36 x 10-19. The density of the air, at the same distance from the earth, would be 3 x 10-846 or 3 × 1027 less than that necessary for the ether, and, beside, we have no evidence that the air is capable of transmitting transverse waves. The coefficient of rigidity of the ether given above may be compared with that of steel, which is 8 x 10", or glass which is 24 × 10".*

The question which next arises is, what evidence do we possess that the luminiferous ether is identical with the medium which transmits electrical oscillations? Evidently, if the velocity with which electrical oscillations are transmitted is the same as the velocity of light, the probability is immensely in favour of the mediums being identical, since the velocity with which a wave is transmitted depends on the ratio of the rigidity to the density. The experiments of Hertz and Lodge have shown that these two velocities are approximately the same. Hertz converted the electrical oscillations, excited by an induction coil and an oscillator, into stationary waves by reflection from a sheet of zine placed at a suitable distance. The length of the wave was then measured by moving a secondary circuit about between the primary oscillator and the reflector until the positions of the places of maximum and minimum disturbance were deter

Encyc. Brit., article "Ether."

† Lodge's "Modern Views of Electricity," pp. 237, 244.

[FEBRUARY 13, 1891.

mined. The wave length and the number of oscillations per second being known, the velocity of propagation could easily be calculated.

One of the most revolutionary conclusions of the modern school is, that the electric energy is not transmitted from the source to the work through the so-called conductor, but through the dielectric medium intervening between the source and the work. This theory was given by Prof. Poynting in 1884, as a necessary development of Maxwell's theory that the electric energy resides in the dielectric medium. As this theory is of great interest and seems to be by no means clearly understood by some of the writers on the Ether question, I shall attempt to give some account of it, though possibly only in a very crude way.

The electric field, due to a static charge, can be divided up into cells, cach containing one unit of energy, by the intersection of unit equipotential surfaces with unit tubes of force. A simple and practical method of representing this structure of the electric field has already been described in the pages of the ELECTRICAL REVIEW. A unit tube of force is represented as an elastic tube, the area of any section of which contains unit quantity of electricity. These tubes are divided up into unit cells by transverse elastic diaphragms which coincide with equipotential surfaces rising one above the next by one unit of potential. The cells are supposed to be filled with an incompressible fluid, and the elastic diaphragms are distorted more or less, according to their position in the field and according as more or less of the incompressible fluid (which is taken to represent electricity) is forced into the terminal cell of a tube of force. If these tubes of force are represented by lines of force, corresponding to their centre lines, it is easy to deduce from this model of the electric field Maxwell's proposition, that in order to account for attraction and repulsion in the electric field, the lines of force must tend to shorten themselves, and must exert an outward pressure at right angles. The pressure of the fluid in a cell represents the potential, and the stretch on any diaphragm the electric force at any given place.

With the help of this model we can form a tolerably clear idea of the nature of Poynting's theory. Taking first the case of the Leyden jar, or Condenser: fig. 1 represents a section of two conducting plates, A and B, one charged with positive electricity and the other negative, the space between the two being occupied by a dielectric such as air. The fine lines represent the traces of equipotential surfaces on the plane of the paper. The lines of force are not drawn on the diagram, but they can be easily imagined by remembering that they run everywhere at right angles to the equipotential Ines. If the positive charge is on A, the lines of force pro

FEBRUARY 18, 1891.]

The energy of the electric field may be considered to have been stored in the first place in the dielectric between the plates A and B, but part of it has now been transferred to the external electric field. By far the greater part of the energy, however, still remains between the plates A and B, for it is evident that by far the greater number of the cells which would be formed by drawing the lines of force would lie between A and B.

Consider now what will take place if the plates are connected by a conductor, c. For simplicity the conductor will be taken to lie along a line of force, and to be of so great resistance that the position of the equi-potential lines will not be perceptibly disturbed when the current is flowing. The essential difference between a conductor and a dielectric is that the former offers little or no elastic resistance to the flow of electricity, or may be looked upon as incapable of sustaining a stress in the electric field. Connecting the two plates of the condenser by a conductor, may be looked upon as analogous to what takes place when the chain of a watch breaks while the mainspring is wound up; the energy stored up in the coiled mainspring is given out to the barrel, and if a brake were pressed on the barrel with the proper force the whole of the energy of the spring would be converted into heat. In a precisely analogous way the energy on the strained dielectric is converted into heat in the conductor. In the first place, the energy in the external field nearest to the conductor will be used up, or, more strictly speaking, transformed. This will then draw a fresh supply from the reservoir of energy between the plates A and B, and so on till the whole of the energy in the electric field is given up to the conductor.

The important question now arises, what path does the energy follow in passing from the source of energy to the conductor. Poynting's theory is that the electric energy moves at any point in a direction perpendicular to a plane containing the electric and magnetic lines of force at that point. As the magnetic lines of force are circles, the centres of which lie in the conductor, the plane in question will be tangent to the circular line of force passing through the given point, and the perpendicular path in which the energy flows will be tangent to the equi-potential plane passing through the point, and will be directed towards the conductor. This may be stated shortly by saying that the energy moves at each point along the equi-potential surface passing through

the point, and in a direction towards the conductor, where the energy is being dissipated or transformed, and away from the source where the energy is being generated. In fig. 1, when the circuit is complete, the energy will flow out from the source, namely, the dielectric between the plates A and B, between the unit equi-potential lines, and enter the conductor, c, everywhere in paths perpendicular to its axis. The energy is supposed to travel in the form of wave motion. Any strained elastic body, such as a spring, when suddenly released from stress at one end, is thrown into a state of vibration and thus it would appear that the energy will be transferred from the source to the external circuit by a series of transverse waves flowing everywhere along equi-potential surfaces into the conductor.

The state of the electric field, and the flow of electric energy in the case of the voltaic cell will now be described.

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In fig. 2, the state of the field before the external circuit is completed, is shown by unit equi-potential lines. It is assumed that the total rise of potential (taken as 8) takes place at the surface between the acid and the zinc; hence the whole of the equi-potential lines pass out from this surface. At the surface between the acid and the copper plate there is a back E.M.F. of say 3; and this reduces the potential of the copper plate and the part of the conductor attached to it to 5. In consequence of what has been said above, it will be evident that the equipotential lines, 7, 6, and 5, converge upon the surface between the acid and the copper. Lines 4 and 1 pass round the open ends of the conductor, and the other lines lie approximately as shown in the diagram. It will be observed that almost the whole of the effective E.M.F. between the copper and the zinc, namely, 5 units, is concentrated upon the thin layer of dielectric between the ends of the conductor, and as this layer is gradually reduced by the approach of the ends of the conductor, the equipotential line 4 approaches and becomes merged in the conductor, and the other lines approach the positions shown in fig. 3, which they finally take up when the circuit is completed.

The electric energy now flows from the surrounding dielectric into the line of weakness represented by the conducting circuit in a succession of transverse waves. The difference, however, between this case and that of the condenser, illustrated in fig. 1, is that the wave energy is continuously supplied, as fast as it is drawn off, by the chemical combination of the atoms of the acid and the zinc, while in the case of the condenser, the supply of wave energy ceased as soon as the strain in the dielectric between the plates had disappeared. Poynting shows that the rate at which energy flows out between any pair of equipotential surfaces is proportional to the difference of potential between the surfaces; hence, if V1 be the total E.M.F. at the surface of the acid and zinc, and v2 the E.M.F. between the copper and acid,

When the resistance of the internal circuit is uniform, as in the case illustrated in fig. 3, the unit equipotential lines intersect the conductor at equal distances; this, however, is not the case if the resistance at different parts of the external circuit varies per unit of length.

When there is an electromotor in the external circuit, there is a counter E.M.F. at the place where the motor is working, and the effect on the electric field is similar to that of the surface between the copper and the acid in fig. 3. A number of the equipotential lines converge on the motor equal to the counter E.M.F. generated by the motor, which number becomes nearer and nearer equal to the total number diverging from the generator or source as the E.M.F. of the motor approximates to that of the generator. In the theoretical case when the two E.M.F.'s are equal, all the equipotential lines. diverging from the generator converge on the motor, and, therefore, no energy flows into the conductor; that is to say, no heat is produced and there is no current. formula for the efficiency of the motor is the same as that deduced above for the similar case of the voltaic cell; and

The

210

this agrees with the formula which has been deduced in this case from Ohm's law.

This is important as showing that the numerical results deduced from the new theory of the electric current are in perfect agreement with the established laws of the old theory.

(To be continued.)

THE BUFFALO ELECTRIC RAILWAY. THE Electrical Engineer of New York, in its issue of January 28th, contains some account of the installation, now in progress, connected with the application of electric motive power to some portion of the tramway systems in the city of Buffalo. The syndicate, which controls this enterprise, represents the consolidation of all the street railways in Buffalo, comprising between 400 and 500 miles of lines.

The electric railway system will consist of about 53 miles of double (or 106 miles of single) track, and will have a carriage service of 300 cars, described as 32 and 34 foot 8-wheeled vestibuled cars.

The plant will include Babcock and Wilcox sectional water tube boilers, with a total heating surface of 12,000 square feet, and working at 175 pounds pressure. At present, the power is composed of six compound engines, made by the Ball Engine Company of New York; each engine is of 250 H.P., and each will drive a 225 H.P. Edison generator. It is intended, later on, to erect an additional plant of eight 300 H.P. compound engines, and sixteen 225 H.P. generators; the power station has been constructed with a view to this increase. The engines have fly-wheels weighing each 15,000 pounds, running at 210 revolutions; the engines complete weigh each 50,000 pounds.

About one-third of the lines will be of centre-pole construction, and the remainder cross suspension. The feed wires will be laid underground, the conduits being of two typesthe wood pulp pipes of the Indurated Fibre Pipe Company, and the cement lined pipes of the Standard Underground Company. These conduits consist of from two to eight pipes each, 2 to 3 inches inside diameter. The feed wires are jute and lead covered cables, and are connected up to the trolley wires at every eight poles, or at about every 1,000 feet. Manholes are located at 380 feet apart, and it has been arranged that all joints are placed at them. In the first installation of 15 miles of double track, there are about 10 miles of conduits, in which will be placed some 40 miles of No. 0000 cable, and 25 miles of feed wires of No. 000, in addition to the overhead conductors.

In the track work, 56 and 60 lb. girder rails, with grooved -tread, are used, with heavy Georgia pine ties placed 2 feet between centres. The pavements are principally of asphalte, and here the rails are spiked directly to the ties, chairs being omitted.

All the construction work, including buildings, power plant, with the steam and electrical equipment, line erection, and conduits, has been executed under the direction of the Field Engineering Company of New York, who are acting as engineers and contractors for the Buffalo Street Railway Company.

POSTHUMOUS SCIENTIFIC HONOURS.

BY S. ALFRED VARLEY.

THE name of William Sturgeon has lately been very prominently brought forward through the medium of the Cantor lectures on the "Electro-Magnet," delivered by Dr. Silvanus Thompson at the Society of Arts last year, and the concluding portion of these lectures brought to my mind the fact that I once had the good fortune to see Mr. Sturgeon. In 1850, "The Researches of Sturgeon," embodying the chief scientific labours of his life, were published in a single volume, and immediately after the book was out of press, Mr. Sturgeon called upon my father, the late Cornelius Varley, to ask him to accept the first copy issued, as a slight recognition of

[FEBRUARY 13, 1891.

services rendered at what was a turning-point in Mr. Sturgeon's life. My father had not seen Mr. Sturgeon for a space of over 20 years, and the meeting between the old artillery soldier and my father in 1850 was a pleasant one to both of them-especially pleasing to my father it was to find that the services it had been his privilege to render had not been forgotten, and very pleasing also that Mr. Sturgeon should have been anxious that the first copy of the crowning literary labours of his life should be presented to my father.

I was reading a few days since the following passage:-"I had rather that one fading bud of kindly sympathy were laid in the palm of my living hand, than that my coffin were shadowed by a pyramid of the costliest exotics that ever burdened with sickly fragrance the chamber of death," and I am of opinion that the hard-working soldier who successfully carved his own way in life would have sympathised with what is expressed in the passage quoted.

In attributing the discovery of the electro-magnet so exclusively to William Sturgeon as Dr. Silvanus Thompson has done, a false impression is given of the history of electromagnetism, and it is contended that injustice is done to other scientific discoverers.

The numerous references to articles in the Philosophical Magazine and other scientific journals which accompany the published report of Dr. Thompson's late Cantor lectures, give evidence of industrious research; and, therefore, it seems difficult to understand how it is that a communication from Mr. Hatchett, which appears in the Philosophical Magazine of January, 1821, and which is headed "Electro-magnetic Experiments of Oersted and Ampère should seem somehow to have escaped attention. In the communication referred to it is stated that "M. Arago magnetised a slip of iron and afterwards a steel wire by putting them in contact with the conjunctive wire (i.e., the conductor closing the voltaic circuit). "A simple method of magnetising a steel needle by the conjunctive wire, consists in placing the needle in the part of the conjunctive wire which is twisted spirally (the italics are the writer's). Whether the needle is placed directly upon the threads of the spiral or enveloped in paper or a glass tube to prevent contact with the conjunctive wire, it becomes magnetised and its north and south poles corresponding to the north and south poles of the terrestrial magnet,will be determined by the direction of the spiral which bears the needle." In another passage in the same communication it is stated that "M. Arago, following the theory of M. Ampère, conceived the idea of twisting a conjunctive wire in the manner of two symmetrical spirals placed one after the other-these spirals differed from each other only as to the direction in which their generating points turned round their hollow spindles; by putting a needle in each spiral the two needles became magnetised at the same time, so that the poles of the same name were contiguous. In transmitting a discharge of a Leyden phial through a copper wire twisted in the same manner of two consecutive spirals, M. Arago has further observed that the steel needles placed in these spirals became magnetised by the electric fluids of ordinary machines as well as by the voltaic apparatus.

The

"Other facts have been long known which prove the mutual influence of the two fluids, magnetic and electric. points of the paratonnerres become naturally magnetised by the electricity of the atmospheric air. M. Arago, in the annuary of January of 1819, states that a Genoese ship on its way to Marseilles was struck by the thunder at a little distance from Algiers; that the needles made a half revolution although the needles did not appear damaged, and the ship struck on the coast at the moment the pilot thought he made the North Cape." In another part of the communication quoted, Mr. Hatchett says "that Oersted showed that the magnetic effects of the electric current depended solely upon the quantity" of the current, and he enters into details showing how Oersted demonstrated that this was so.

The above communication of Mr. Hatchet, published in January, 1821, deserves to be reproduced in its entirety, for it really gives a more complete scientific description of the electro-magnet than is contained in Sturgeon's communica tion to the Society of Arts, of 1825, four years later, and it seems curious that so painstaking a searcher into the records of scientific history as Dr. Thompson should have somehow or other have overlooked Mr. Hatchett's article.

In March, 1822, Peter Barlow describes the star wheel electromotor, and mentions Marsh's name very favourably,

crediting him with original work, and regretting that he was not in a position where his abilities would receive a higher pecuniary recognition.

A Dr. Kraemtz writes to the Phil. Magazine, in 1823, "Immediately after Oersted's discovery, the idea occurred to Prof. Schweigger of increasing the electro-magnetic power by winding the connecting wire of the voltaic battery round the compass-needle, so it will be seen that really a great deal was known in respect to electo-magnetism before the year 1825.

In 1823 Mr. Marsh was awarded the large silver medal of the Society of Arts and a purse of 30 guineas, for his portable electro-magnetic apparatus, and in 1825 Mr. Sturgeon received a similar reward from the Society of Arts for certain advances on Marsh's apparatus.

The following passages relating to the apparatus of Marsh's appear in the Society's proceedings of 1823, written, it is presumed, by the secretary, the late Mr. Aikin :-" Exceedingly interesting and important experiments on the intimate connection between electricity and magnetism mark the principal track of philosophical investigation during the last four years. Prof. Oersted, of Copenhagen, led the way, and was followed with zealous emulation by Ampère, Biot, Arago, in France; by Sir H. Davy, Dr. Wollaston, Prof. Cumming, and Mr. Faraday, and Mr. Barlow in England. The large and costly apparatus employed by most of these philosophers necessarily restricted to a few persons placed in singularly favourable circumstances the prosecution of these discoveries."

"Mr. Marsh, occupying a very subordinate department in the Royal Laboratory at Woolwich, was employed by Mr. Barlow as an assistant in his electro-magnetic experiments, and thus favourably circumstanced, he was induced to turn his attention to the construction of an apparatus capable of exhibiting all the known facts of electro-magnetism, and of enabling the possessor to prosecute further researches in this interesting and important branch of natural philosophy."

"Having succeeded in his object, Mr. Marsh submitted to the inspection and judgment of the Society his apparatus, and before two numerous committees exhibited by means of it, with perfect success, all the facts of electro-magnetism which at that time had been discovered."

From the official description of Sturgeon's apparatus, contained in the Society of Arts Proceedings of 1825, it would appear not to have attracted so much attention as that of Marsh's, which preceded it. The opening passage reads as follows:

"Mr. Marsh's apparatus for the same purpose as Mr. Sturgeon's was rewarded by the Society in the session before last, the battery consisting of plates presenting eight surfaces of about a square foot each, was the smallest that had at that time been applied to electro-magnetic researches; the rest of his apparatus was such as had already been used by Ampère, Davy, Barlow, Faraday, and others."

"Mr. Sturgeon's apparatus is even more portable than Mr. Marsh's, and is better fitted than that, for the use of the lecturer." Sturgeon's battery is then described as being similar to Prof. Hare's calorimotor, and it is added "that Mr. Sturgeon has very judiciously chosen to have small galvanic power assisted by strong magnetic power (the italics are the writer's), rather than the reverse, as is usually the case this has enabled him to economise the size of the battery, whilst the increased magnetic power is obtained at a small first expense, and needs no renewing.'

Mr. Sturgeon's letter to the secretary of the Society of Arts, when submitting his apparatus and bringing it under the notice of the Society makes no reference whatever to the electro-magnet, and neither do the three certificates of Profs. Christie, Gregory, and Mr. Barlow, annexed to Sturgeon's communication, make any mention of it. The chief claims put forward are the substitution of powerful magnetic force for that of large battery surface, and also the superiority, on account of its larger size, of Sturgeon's apparatus over that of Marsh's for lecture purposes.

The electro-magnet forms part of Sturgeon's apparatus of 1825, and is described without comment in the same way as the rest of the apparatus, but Mr. Sturgeon would seem to have been the first to make a horseshoe electro-magnet, and to point out its power to lift a considerable weight. Dr. Silvanus Thompson states that the electro-magnet forming part of Sturgeon's apparatus rewarded by the Society of Arts lifted 9 lbs.

Now, it can be of no possible benefit to those who have

211

passed away whether they be praised or blamed by those who come after them, but the history of scientific advances is of value to the living if it be true history, and Dr. Silvanus Thompson seems to have dealt with the claims of Sturgeon too much in the same way as a barrister does when defending a client. As an example of this, Dr. Thompson, when describing the original horseshoe magnet of Sturgeon, says "it was coiled with a single spiral of stout uncovered copper wire of 18 turns." I myself well remember seeing Sturgeon's apparatus in the Society of Arts Museum, and speaking from memory, the gauge was No. 16 B.W.G., the size at one time almost universally adopted for electrical purposes, no doubt because it was the size used for bell hanging, and therefore in the market.

Now, Dr. Silvanus Thompson says, "this coil was found appropriate to the particular battery which Mr. Sturgeon preferred. Surely this is special pleading. What Sturgeon attached so much importance to was the reduction of battery surface with the twofold view of lessening the inconvenience arising from battery fumes, and at the same time reducing the cost incidental to a large consumption of chemicals.

The battery employed by Mr. Sturgeon exposed only about one-ninth of the surface of the battery employed by Mr. Marsh, and had Mr. Sturgeon been acquainted with what is now known to even "half-educated electricians" of the present day, we may be very sure he would have increased the number of convolutions surrounding his soft iron core.

(To be concluded.)

ELECTRICAL STANDARDS COMMITTEE.

THE following resolutions are to be submitted to the next meeting of the Committee, to be held on Friday, the 20th February :

1. That it is desirable that new denominations of Standards for the measurement of electricity should be made and approved by Her Majesty in Council, as Board of Trade. Standards.

2. That the magnitudes of these Standards should be determined with reference to the centimetre as unit of length, the gramme as unit of mass, and the second as unit of time, and that by the terms centimetre and gramme are meant the standards of those denominations deposited with the Board of Trade.

3. That the Standard of Electrical Resistance should be denominated the ohm, and should have the value, 1000,000,000 in terms of the centimetre and second.

4. That the resistance offered to an unvarying electric current by a column of mercury of a constant cross-sectional area of one square millimetre, and of a length of 106.3 centimetres at the temperature of melting ice may be adopted as one ohm.

5. That the value of the standard of resistance constructed by a Committee of the British Association for the Advancement of Science in the years 1863 and 1864, and known as the British Association unit, may be taken as 9866 of the ohm.

6. That a material standard constructed in solid metal, and verified by comparison with the British Association unit, should be adopted as the Board of Trade standard ohm.

7. That for the purpose of replacing the standard, if lost, destroyed or damaged, and for ordinary use, one or more copies should be constructed, which should be periodically compared with the standard ohm and with the British Association unit.

8. That the standard of electrical current should be denominated the ampère, and should have the value one-tenth (0.1) in terms of the centimetre, gramme and second.

9. That an unvarying current which, when passed through a solution of nitrate of silver and water containing from 15 to 20 parts by weight of nitrate of silver in 100 parts of water, deposits silver at the rate of 0.001118 of a gramme per second may be taken as a current of 1 ampère.

10. An alternating current of 1 ampère shall mean a current such that the square root of the time average of the square of its strength, at each instant, in ampères, is unity.

11. That an instrument contructed on the principle of the balance, in which by the proper disposition of the conductors

212

forces of attraction and repulsion are produced which depend upon the amount of current passing, and are balanced by a known weight, should be adopted as the Board of Trade standard for the measurement of 1 ampère, whether the current be unvarying or alternating.

12. That the standard of electrical pressure should be denominated the volt, being the pressure which, if steadily applied to a conductor whose resistance is 1 ohm, will produce a current of 1 ampère.

13. That the electrical pressure at a temperature of 62° F. between the poles or electrodes of the voltaic cell known as Clark's cell, constructed and used in accordance with the specification attached to these proceedings, may be taken as not differing by more than * parts in one thousand from a pressure of volts.

*

REMARKS ON THE REPORTS CONCERNING EXPERIMENTS AT OERLIKON.

[FROM A CORRESPONDENT.]

THE experiments which have been proposed with reference to the projected utilisation of the water-power at Laufen on the Neckar for the Frankfort Exhibition by means of an electrical transmission actually took place on the day appointed, January 24th, and the reports in the daily pressrather meagre, certainly, from a technical point of view-are full of enthusiasm over the decided success of the experiments. The Frankfurter Zeitung, which was represented on this occasion by a special reporter, gives a very lengthy account of the proceedings, from which we learn that the tension of 30,000 volts was not obtained in the generator itself, but by means of a transformer which converted the 100-volt current of the generator into a current of high tension. This arrangement is certainly necessary for the Oerlikon machines with rotating induction coils. But in a rational and suitably constructed alternating current machine with fixed induction-coils, the production of a 30,000-volt current (with proper arrangements for insulation) would present no difficulties, and consequently the transformation in the production of the primary current would be unnecessary.

According to the reports in the daily press, the conduction over a distance of 7 kilometres was effected for the experiments by conveying the cable over 27 supports on 108 (?) insulators at distances of about 30 centimetres. As the experiments were intended to furnish a practical proof that the conduction of a current of 30,000 volts to very great distances presents no difficulties if proper arrangements are adopted, the question involuntarily occurs whether the experiments at Oerlikon, in which a cable-distance of 7 kilometres was artificially produced within a relatively very small distance, in fact, justifies valid inferences as to the phenomena which would occur on account of the varying atmospheric influences in grappling with a real distance of 180 kilometres.

The further communications of the reports which have appeared hitherto, extensive as they are, contain scarcely anything which could enable the technicist to form even an approximate opinion as to the value and the results of the Oerlikon experiments, Thus, e.g., there is a report on the precautions taken against accidents to the conductors. But in this part of the report we find nothing save an account of the well known effects of the safety wires everywhere in use in transformers.

As an illustration of what must be thought of the reports in the daily Press concerning important phenomena in the technical sphere, I will quote the following passages from the report of the Frankfurter Zeitung :

"In its conduction, and about in its middle, between two of the parallel wires, a connection was effected, but for the present it was not closed; only two pieces of wire were bent towards each other, and their ends were approximated more and more up to such a distance that an over-springing of the spark might be expected. When the machine was set in action the spark leapt over at the distance of 22 millimetres. This is much. It has been hitherto assumed that a few

• Blanks are left here in the report sent to us.-EDS. ELEC. REV.

[FEBRUARY 13, 1891.

millimetres suffice (?) It is now demonstrated that a current of 22,000 volts does not spring over until the ends or the projections of the wire approach each other at the relatively great distance of 22 millimetres. The fabulous extreme danger of high-tension currents is reduced to nothing."

The only novel fact which we gather from the reports on the experiments at Oerlikon is that the transformers for the above-mentioned high-tensions are placed in oil insulators. I have learnt besides, through a private channel, that the starting of the motors for the intended transfer of power is proposed to be effected by means of steam engines, which are to serve to bring the motor up to the required number of rotations before it is inserted in the circuit of the current. I must here not omit to mention that some time ago experiments were made by the firm "Helios," of Cologne, with alternating currents of a tension exceeding 20,000 volts, which yielded results concerning the striking distances of the sparks very different from those reported by the Frankfurter Zeitung at the Oerlikon experiments. I refer on this subject to the communications of Herr August Schneller in the Elektrotechnische Zeitschrift of November 7th, 1890, from which it appears that the spark strikes over 28 millimetres at 15,000 volts, and at 20,000 volts over about 64 millimetres.

Until we receive complete details concerning the electrical data, we must conclude from the very general reports of the political daily Press that nothing has happened at Oerlikon which supplies technically valid proof that the conduction of a current of 30,000 volts to a distance of 180 kilometres is permanently practicable with the appliances hitherto known. If this is still possible, means must be brought into play for this purpose, concerning which nothing is revealed in the reports which have appeared concerning the experiments at Oerlikon.

Nevertheless, electricians-and especially the representatives of the systems of transferring power to a distance-feel obliged to the daily Press for having taken such an interest in the Oerlikon experiments and excited such commotion in extended circles of readers, since thus the general public is familiarised with the thought that electric currents of very high tension may, and should be, made industrially serviceable. In this manner electro-technics, which have still to contend against a deeply-rooted distrust, will reap an important benefit. The Oerlikon Company merits gratitude as having given a salutary direction to public opinion by grandly-conceived and ably-executed experiments.

LONDON COUNTY COUNCIL.

Ar the weekly meeting, held on Tuesday, the report of the Highways Committee was submitted.

Use of Subways by Companies and others.

We have proceeded upon the reference made to us on the 2nd of December, on the recommendation of the Improvements Committee. to consider and report upon the advisability of the council applying to Parliament for powers to compel gas, water and other companies to place their pipes, wires, &c., in the subway of Rosebery Avenue, and to enable the council to charge a rent for such user. We are advised that the council has at present no powers with reference to these matters, and that such powers cannot be obtained during the present session, as due notice has not been given of the intention to apply for them. It will be remembered that last session the Council's Subways and Overhead Wires Bill, as originally introduced, sought power to compel companies to place their pipes in subways already existing, as well as in subways to be constructed under the powers of the Bill; but that in consequence of the uncompromising opposition of the gas and water companies, that part of the Bill had to be abandoned. The Overhead Wires Bill of this session provides that where the council has a subway in any street any wires over the street which can be conveniently removed into the subway shall be so removed, and that the council shall charge a rent for the use of the subway; and in the Electric Lighting Orders provision is made for the laying of the mains in existing subways and for the payment of rent. We propose to consider in what way the objections of the gas and water companies to the laying in the subways of any new pipes which may be required may be met; and when the proper time arrives we hope to be able to advise the council whether, and if so in what way, the object of the reference may be effected. We may mention that, in our opinion, any application on the subject which may be made to Parliament should have relation to all the subways of the council, and should not be limited to that in Rosebery Avenue.