are water supply. Inside the case is a thin drum of considerable diameter, on the circumference of which are small double buckets. The water entering by the supply pipe impinges with force on these buckets, and drives the wheel with considerable rapidity and power. The water falls out of the exhaust, and is run away or can be led into cisterns for other use. The shaft and all wearing parts of hardened steel, gunmetal, and brass, fitted with an efficient system of oil-cups and locknuts. The cover is easily removable for inspection and repair, but the mechanism being very simple, the motor will run for months without attention other than turning on or off the water and occasional supply of oil. It makes no noise, starts easily, occupies exceedingly little floor space, and is of high efficiency. These motors are very cheap, the price being only £1 for the smallest man, and £3 for two man power, the latter size being capable, with larger supply pipe, of working up to five man or even 1 h.p. The following are details of the motors : electrical engineers to justify a short account of it being brought before the Institution." The more important conditions imposed in designing the apparatus were that: 1. All measurements made must be capable of verification at any time by a direct comparison of certain resistance coils with a standard ohm, and of a constant potential difference with a standard cell; and that the arrangements should allow of these comparisons being made quickly for the satisfaction of those interested in the accuracy of the measurements. 2. Volts and amperes must be indicated by direct deflection observer by torsion arrangements or otherwise; and the value on a scale, and no balancing operation be required from the of the readings must not be influenced by the working of dynamos or the moving of large masses of iron within a few yards' distance. 3. The ammeter as well as the voltmeter must be left in circuit permanently during trials of any desired length. 4. The errors to which the measurements are liable should not exceed 1-5th per cent. 5. The range such as to allow of measurements being made of pressure from 1-1,000th part of a volt to 700 volts, and of current from 1-40th of an ampere to 1,100 amperes. 2. APPARATUS REQUIRED. The complete apparatus comprises the following: I.-For Measuring Amperes. 1 D'Arsonval galvanometer. 1 high-resistance box, adjustable by the unit, for use in series with galvanometer. 1 rheostat of platinoid strips for carrying the main current. II.-For Measuring Volts. 1 D'Arsonval galvanometer. 1 high-resistance box, adjustable as above, for use in series with galvanometer. A Wheatstone bridge box is used for this purpose. 3 The motors have been used for telephone dynamos and small electric light installations up to 50 c.p. When worked from the Hydraulic Supply Company's mains they will indicate up to 5 h.p. on the brake, and the cost of running is 25 per cent. less than a gas engine, while the first cost is not to be compared. The running of dynamos is very smooth and regular, equal to that of a high-class steam engine. A "Demon" water motor can be seen in Manchester driving a small Manchester type dynamo. 1 Clark standard cell containing two elements. The maker of these water motors is Mr. P. Pitman, Aubrey-road, Withington, Manchester. DESCRIPTION OF THE STANDARD VOLT AND AMPERE METER USED AT THE FERRY WORKS, THAMES DITTON.* BY CAPTAIN H. R. SANKEY (LATE R.E.), MEMBER, AND F. v. ANDERSEN, ASSOCIATE. 1. INTRODUCTORY. It is well known to many electricians that Messrs. Willans and Robinson have established at their works at Thames Ditton a complete arrangement for measuring accurately the steam consumption of their engines. To obtain the efficiency of combined sets of engines and dynamos, measurements must of course also be made of the electric current and pressure, and it was found that even the best ammeters and voltmeters in the market could not be relied upon to give the same degree of accuracy as was obtained in the steam-consumption measurements. Moreover, all such instruments laboured under the disadvantage that they were calibrated elsewhere, so that the results were dependent upon other people's measurements to a degree which was thought to be undesirable. After a series of investigations-commenced as early as 1887-into the question of the class of apparatus which would be most likely to give satisfactory results under the special circumstances, a scheme was drawn up in 1889 for a complete apparatus for measuring currents, differences of potential, and resistances, and the various instruments were designed and ordered. It was not, however, until the beginning of the present year that time and opportunity were found to have the apparatus put to practical uge, various additions and improvements being introduced as the work proceeded. As will be seen in the sequel, no new principles have been introduced in electrical measurements with the present apparatus. It was thought, however, that a complete set of workshop instruments, fulfilling the conditions for high accuracy, and yet possessing the simplicity required for everyday use in an engineer's shop, would be found of sufficient interest to potentiometer rheostats, 250 ohms each, made of platinoid wire on screwed slate rods, carrying capacity up to one ampere. 1 standard ohm. III.-For Calibration. 1 standard rheostat of five platinoid strips, arranged for coupling in parallel or series, each strip capable of carrying 10 amperes. 1 mercury rheostat, capacity 50 amperes. 1 secondary battery, three large cells (15L E.P.S.). 1 key with double set of contacts, for use with standard cell. 1 resistance coil, 10,000 ohms, for use with same. 2 1-9 shunts for galvanometers. IV.-General. Leclanché cells for bridge test, keys, ebonite pillars for connections, etc. The methods of using the apparatus for actual measurements will first be described, after which the calibration of the galvanometers and the verification of the various resistances will be discussed. 3. MEASURING AMPERES. The The apparatus used for this purpose is shown on Fig. 4, with the connections in red. On the same figure is drawn the voltmeter arrangement, in order to give the general arrangement of the whole set of instruments. The circuits of the voltmeter arrangement are in black. It will be seen on Fig. 4 that for current measurements the method of measuring the fall of potential across a known resistance has been adopted. The measurement of this resistance-i.e., the resistance of rheostat B, Fig. 3 and Fig. 4, which, of course, must be made with great accuracy-could not be taken satisfactorily by a Wheatstone bridge, owing to its small value (about 001 ohm). method adopted for this purpose will be described further on. The scale of the D'Arsonal galvanometer, G1, has, in addition to the ordinary millimetre scale, another scale graduated to read from 0 to 1,100 amperes, on which the divisions are proportional to the corresponding currents through the galvanometer, the relation or constant connecting the deflections with this current being known from the calibration of the galvanometer. By modifying the resistance, R, used in series with the galvanometer, the constant of the ammeter can be modified to suit the number of amperes to be measured. If k=current through G per unit deflection on ampere scale ; G= R= = in series with galvanometer; even a third rheostat, P, and P2, each of 250 ohms, can be joined in series with P, and so the potentiometer factor altered from 1-100th to 1-200th or 1-300th. Further alterations can, of course, be made in the voltmeter constant by varying the resistance, R, as in the case of the ammeter. The potentiometer factor is evidently independent of the temperature of the rheostats P. The temperature correction required in R is simply 023 per cent. of R*+ 388 per cent. of G per deg. C. of variation. It will be seen that for the ordinary ranges the resistance of the galvanometer-about 435 ohms-is very small compared with R, and that therefore the errors in the measurements due to unavoidable small errors in the estima tion of the temperature of R are quite insignificant. If f=potentiometer factor; G=ohms resistance of galvanometer; R: = in series of galvanometer; (G+R) k D=ƒ KD ; .. RK-G (3) 1. For the galvanometer, at the rate of 1.66 ohms per deg. C. k=1 micro-ampere = 1 x 10-6 amperes; G=435 ohms (legal) at standard temperature; therefore, the resistance, R, to be used in series with the galvanometer to obtain different voltmeter constants=ƒ K-435. Table II. contains, in column 1, the constants used with the instrument; in column 2 the corresponding values of R; and in 3 the value of the temperature correction in ohms per deg. C. deviation from the standard temperature-17 deg. C. Ammeter constant, K. ohms. C. of rise in B. 1 17,708 4.17 + γ + γ = 0.417 + γ γ = C2 × 2 × 105 deg. C. Voltmeter R For ordinary work the readings on the scale are amply accurate, as they can be depended upon to be within 3 per cent. of error. For very accurate trials, however, the scale is used only to ensure the practical steadiness of the load, and for taking readings at short intervals in order to obtain the mean reading. The current corresponding to this mean reading is then determined by direct comparison with the standard ohm and cell. This determination of the current is made by substituting in the galvanometer circuit an E.M.F. equal to that of the standard cell for the P.D. on the terminals of B, and then, by shunting the galvanometer and adjusting R, reproducing the deflection in question. If, then, The apparatus for this purpose is shown on Fig. 4 (with connections in black) in a diagrammatic form. It consists of a ¡D'Arsonval galvanometer, G, with a resistance, R, in series, and a rheostat, P, connected with the difference of potential eads for instance, with the terminals of a dynamo. The scale of the galvanometer has a second graduation constructed in accordance with a calibration, so as to have its divisions proportional to the corresponding currents through the galvanometer. This proportional scale is divided from 0 to 175 volts, and unit deflection on the volt scale is produced by a current through the galvanometer of one micro-ampere. In measuring P.D.'s smaller than one volt, the rheostat P is not used, but the P.D. to be measured is directly connected into the circuit of G2. When measuring P.D's higher than one volt, the P.D. to be measured is connected across the rheostat P, of which a small section-"a" on Fig. 4-is connected with the circuit of Gg. This section "a" is so adjusted as to be exactly 1-100th part of the total resistance of P+ the dynamo leads, which sum is 250 ohms. NOTE. The resistance, R, by formula (3) is, of course, in true ohms; the amounts of R in Table II. are given in legal ohms, as the resistance-boxes available were adjusted in legal ohms. For the purpose of reduction, one legal ohm has been taken = '9977 ohm. The figures have further been reduced about 1-2 per cent. to balance a change of constant. The strongest current which at any time will pass through the galvanometer circuit is the current which deflects to the end of the scale, or 000175 ampere. The heating caused by this current in the galvanometer, as well as in the resistancebox, coils is quite inappreciable, and the galvanometer may therefore be left "on" for any length of time. For everyday work the scale is used, the readings being well within 3 per cent. of error. For more accurate work, however, readings are taken at intervals, and the mean reading is afterwards calibrated against the standard cell as follows: The determination of the P.D. corresponding to the given mean deflection being made by substituting for it an E.M.F. equal to that of the standard cell, shunting the galvanometer, and adjusting the resistance in series with it till the deflection is produced. Then, if R+G ram R1 + G e (4) [The figures referred to will be given in the conclusion of the paper next week.] (To be continued.) * The coils being made of platinoid wire. THE ELECTRICAL ENGINEER. Published every Friday. Price Threepence; Post Free, Threepence Halfpenny. 473 477 ... 463 Watt's Electrolytic Zinc Processes 474 476 Mechanical 470 Provisional Patents, 1891 TO CORRESPONDENTS. 478 478 480 480 All Rights Reserved. Secretaries and Managers of Companies are invited to furnish notice of Meetings, Issue of New Shares, Installations, Contracts, and any information connected with Electrical Engineering which may be interesting to our readers. Inventors are informed that any account of their inventions submitted to us will receive our best consideration. FOLLOW AFAR. I: When Frenchmen initiate an electrical exhibitin at Paris, a congress or conference follows as a matt of course. When Germans initiate an exhibition F Frankfort, the inevitable congress is also held. Whe Americans condescend to go in for a universa exhibition a congress will be a necessity, and we m3. be sure that it will be thoroughly organised and s successful. By the bye, has any student of langusnoticed how rapidly Americanisms are becoming common? This is largely due to the faet, no matte how we may kick against it, that America becoming the centre of the world's action. newspapers initiate new departures, and the CI World copies, sometimes with acknowledgement more often without. Hence we, too, often "locate an engine instead of " place "the engine. Is "location," not its position or "situation," is good bad, or indifferent. It is the Chicago "Exposition," not the old English" exhibition," and so on through 480 the whole gamut of newspaper literature. Ther again, many people in this country have suggested the necessity of meetings somehow and somewhere of the "conventions" kind so common in America, where papers on practical questions are read and discussed. The English characteristic is to pretend all one's manufacturing and constructional details are of immense value, and keep them absolutely secret. The Englishman, in fact, pretends to a supernatural knowledge of details over and above his ridiculous, for there is no single practical detail that fellow. This secrecy about matters electrical is is not easily made clear to anyone who likes to || investigate. As for the nine hundred and ninetynine paper details, many of which find their way to the Patent Office, they are not worth the paper they are written upon. We contend, then, that the Englishman might well be as free with information of his manufacturing and constructional details as is his American brother. The Institution of Electrical Engineers has in a small measure broken down a few of the old traditions, and many, if not most, of its papers are now more practical in character than they were a few years ago. But there is still too much of the scientific society about them. The attempt at trimming is not always happy, and many would be better with the science cut out and the practice left in. We are convinced that the young electrical engineer will learn more from the practice of the older members than he will from their science. It is time it was instilled into him from headquarters that science teaching varies with every new practical departure, and that business consists of practice, not dreaming after the departure has taken place. There is to be an exhibition at the Crystal Palace in the New Year. We would suggest to the organisers of this exhibition that some attempt be made to get up an "English congress" in which the papers read should be intensely practical, and that theorising should be entirely tabooed. Let us have simple do that, how this is done and how that is done, what result is obtained by this combination and what by those combinations. We do not care for the moment what ought to be done, or what ought to be the result-we want to know the actualities of the case. For example, we do not believe one single central station authority is prepared to publish the exact truth as to the losses between the generation and the selling. They will all tell you the efficiency of this machine and that machine, of the theoretic loss through leads, wires, and connections - but that is all. We do not know the actualities of any single case. The same holds as regards motive power, traction, its cost and its returns. Almost all our figures on these points are from American sources. The Institution is about to commence its autumn session. Will it be as it has been, that at least half the hearers are guests, and not members, students from schools, who are told it is the thing to attend the meetings? No doubt the room is thus filled; but does absence prove that members are interested in the papers read and discussed? The Crystal Palace authorities would be wise to spend £100 or so upon the preparation of half a score of papers upon practical points by practical men, if they cannot manage a new departure without. Can they get the truth about the use of secondary batteries in traction work? Many of us have a pretty good idea of how the facts stand, but no official or authoritative statement. The result of their use is either good or bad. If the former, why this secrecy; if the latter, what is the use of pretending they are what they are not? Time, and a very short time, will show the want of success. Meanwhile men are waiting authoritative figures, and business is delayed and lost by silence. side of the alternate currents have always to deal with the fact that they cannot possibly sell more than a certain not too high percentage of the current generated, and that engines constructed to run economically at full load are both wasting capital and coal when running at anything beneath this full load. What reason is there that the rival camps may not join forces, in cases, at least, where electrical energy has to be transmitted over some distance, or where natural forces are open to be utilised? Why not, it may be asked, generate your energy in alternating currents, and transmit it at high pressure, commute the currents not at the generating but at the receiving end, and use this continuous current to charge accumulators? Engineering difficulties— too complicated, is the answer. Well, in one way, this answer is sufficient. con A scheme was announced some time ago by a sanguine young electrical engineer-Mr. Pritchett, if we rightly remember-somewhat on these lines. The large engines, he maintained, which were always necessary for alternate-current distribution, never worked on an average over 30 or 40 per cent. of their full power. He proposed to use either an engine or water power continuously to drive an alternate-current dynamo, receive the current at an alternating-current motor, which would drive a continuous-current dynamo which should tinuously charge accumulators; these during the night would drive a continuous-current motor, and this again drive an alternate-current dynamo, and so distribute to transformers at the private houses. By working the turbine or engine at full power the whole time, it was expected that a gain on both first cost and in efficiency would yet be obtained. We are not aware whether this scheme was ever tested, but it is pretty evident that such a complicated system would not gain the support of central CHARGING ACCUMULATORS BY ALTERNATING station engineers. CURRENTS. The facility of transmission of electrical energy by high-pressure alternating currents, together with the ease of transformation of pressure up or down, seems to indicate the alternating-current system as that best to be used for transmission of power over distances, and thus for the utilisation of natural forces. The continuous-current system, by reason of the possibility of storing the energy by charging accumulators, equally seems to indicate the continuous-current low-pressure system as that best to be used for regular and constant system of electric light in towns. Electrical engineers have too long been divided into rival camps upon this question-one apparently absolutely avowing belief in no system that uses alternate currents, and the other as positive that the use of storage batteries is a mistake. Those who have committed themselves on the side of continuous currents, too often seem to forget that all dynamo armatures in reality produce nothing but alternate currents, and their devotion to continuous currents is but to the enemy under another name. While those who have allied themselves exclusively on the The question has, however, recently been modified by the introduction of a new factor, which may render a reconsideration of the problem necessary, due to the initiative of Messrs. Schuckert at the Frankfort Exhibition. Messrs. Schuckert exhibit dynamos, each of which will act either as generator or motor, and will produce either alternate or continuous currents at will. It will act as an alternate-current motor, and yield either power or, if desired, continuous currents direct without further apparatus. The principle of the machine is ridiculously simple, and it is a wonder why no one ever thought of doing the thing before. Every Gramme ring produces alternate currents when rotated; these are commuted into continuous currents at the segments of the commutator. If, however, the currents were also led to a set of ring collectors, evidently the dynamo would produce alternate currents. By arranging four connections at points at right angles to each other from the ring, these alternate currents will differ by 90deg. in phase, and produce a rotating field if led to a similar armature of a second machine. If the field magnets of this second machine were excited by a continuous current, this second machine would, and does in practice, act as an alternating-current motor. But being rotated in a magnetic field it will give off alternate currents from its coils exactly as when rotated by an engine, and if these currents are commuted by the ordinary armature these currents will be continuous currents, part of which can be used to excite its own magnets in shunt, and the remainder can be used for charging accumulators. All that is necessary to effect this change is to add four ring collectors to an ordinary shunt machine. Such motors were at work at Frankfort, and from these at will could be taken alternate currents, direct currents, or power from the pulley. Here we have a machine which evidently brings the problem stated at the beginning of the article within easier reach of solution. Highpressure currents can be generated, using the engine at full power continuously. These can be received by a double-commutator dynamo, taken off as direct currents and used for charging accumulators, from which the supply would be drawn off as required, upon the three-wire system. For stations in the centre of their district this system offers no advantages, but for those at which water or other power at a distance is to be used (and it would be well, theoretically, to have all generating stations away from the houses) the method seems to offer very considerable advantages, and as a means for reconciling the two rival camps, if it prove practical and efficient, must be hailed with pleasure by all who wish the extended success of both. TELEGRAPHS AND GALES. The following from the Times of November 12, A.D. 2,000, cannot but prove of interest at the present juncture: "A furious gale, amounting in some places to a hurricane, raged along the south and eastern coasts during the last two nights, causing a large amount of suffering and damage to shipping, besides many land casualties both in this country and on the Continent. Fortunately, we are able to give full reports of the damage done, as well as to continue the full publication of telegrams from the Continent and America owing to the underground land telegraph lines which were recently completed. Indeed, it is difficult to conceive of the state of mind that so long allowed the uncertain communication of overhead wires alone to continue, by which any gale or snowstorm of more than usual force would throw down the lines and destroy all telegraphic communication with the Continent and the West of England and America within a few hours. It could not be maintained that the additional cost of a few trunk underground wires was too great for the Government to undertake, for the question was one of national importance. The Commission, which at last was obliged to be forced upon the Department, found, as will be remembered, overwhelming evidence of the immense losses to commercial and national interests which occurred at every total interruption of the great telegraph lines through the accumulation of messages, often of the utmost and vital importance. In Germany the wires were already placed underground for war purposes, and the conclusion at last arrived at, that an undertaking Germany could accomplish for war purposes Great Britain could certainly carry out for commercial purposes, has been abundantly justified by the admirable way in which the service has been continued without interruption during the late stupendous gales. It is also a matter of the utmost significance that the greatly reduced list of total wrecks and casualties which have occurred this season is almost entirely owing to the admirable system of coast guard, lighthouse, and lifeboat intercommunication by telegraph and telephone, which has at last been established." MAGNETIC RELUCTANCE.* BY A. E. KENNELLY. The science of magnetism was a collection of facts concerning magnets until Coulomb first brought to light a quantitative relation between a few of its phenomena, and determined by measurement that the forces of attraction or thus entitled it to appear among the exact sciences. He repulsion between the poles of long, thin bar magnets were proportional to the strengths of those poles, and inversely to the square of their intervening distance. In one respect it has since been shown that the discovery was unfortunate, for it served to depress rather than to stimulate further enquiry into the laws of quantitative magnetic relationships. The application of Coulomb's law gested, perhaps, by the analogy the law bears to that of soon brought into use a conception of magnetism, suggravitation force. This was the hypothesis of a layer of fluid or imponderable matter resident on the surfaces of magnetic bodies, and endowed with attractive and repellent forces on all portions of such fluid in exact similarity to the two-fluid theory of electricity. Each element of surface magnetism upon every other element of its own, or of other magnet would exert, according to Coulomb's law, a definite force surfaces, and when the distribution of the magnetic matter or fictive layer was known, the total forces active between the summation of all the elementary actions. This was the magnets forming the system could be determined by the polar conception and mathematical theory of magnetism. It was not only artificial; it was also misleading. It assumed that definite action could be exerted at a distance, theless, a slight modification of the polar theory rendered ignoring the action of the intervening medium. Neverit capable of expressing a mathematical theory of magnetism with apparent success, and exhibits in this respect, like the purely artificial frameworks of thought, void of all attempt theories of gravitation, the remarkable construction of at reality, yet capable of affording useful applications and exact quantitative results, while beneath their foundations the real and natural active forces still lie in undiscovered concealment. It was soon apparent that magnetism considered as a fluid could not be confined to the surface of bodies, since it was only necessary to break a ar magnet asunder in order that new poles and new magnetic fluid should be exhibited. The amendment to the original theory was then framed that a condition of molecular magnetisation extended, veinlike, throughout the substance of the magnet. The termination of each vein at the surface exposed a definite quantity of polarised magnetic matter, while within the veins the polarity was neutralised by the successive layers of opposite molecular poles. This was a great stride beyond the original theory, for it ascribed magnetism not alone to a fictive superficial layer, but to the combined effects of all the molecules in the magnetised body, whose substance, no neers, October 27, 1891. Paper read before the American Institute of Electrical Engi |