THE ELECTRICAL TRANSMISSION OF POWER FROM NIAGARA FALLS.-III.

BY PROF. GEORGE FORBES.

PARALLEL WORKING.

ENGINEERS in America have had no experience in actual commercial conditions of parallel working with alternators. This is partly because the machines which have been made in that country do not work so well as some others in parallel. In the case of the transmission from Niagara Falls my opinion is that parallel working will give the best results. If this arrangement were not adopted it is obvious that when the dynamos are loaded up as much as possible they could never be all fully loaded. It is also quite obvious that if our conductors are to be carried through subways the space required becomes quite excessive unless we adopt parallel working. The complete success of parallel working between Tivoli and Rome left no doubt as to the feasibility, besides the desirability, of adopting parallel working. The reduction in frequency which we have made assists very considerably in this result, and it says much for the American manufacturer who has received the contract that, although parallel working with multiphase machines has not been adopted in the past, he is ready to guarantee the performance in this respect of the machines which are to be built for us.

The rules which govern the construction of machines which shall work well in parallel are not very clearly understood. The only fact which has been perfectly established in practice is that the lower the frequency, the more efficient and sure is the parallel working. It certainly depends to some extent upon the amount of self-induction and the amount of mechanical momentum in the machines. It is also certain that if the self-induction of the machines is too high they will not work well in parallel. Of all machines which have been constructed, those which work the best in parallel appear to be those of Ganz & Co., Mordey, and Elwell Parker, but there are many others which do extremely well. It is, at present, not possible to state exactly the conditions which are necessary, but I may say that, generally, a machine with a stiff magnetic field works better than one where the iron is far below magnetic saturation. In judging whether a machine of a particular type will or will not work in parallel, I think one must be generally guided largely by one's own personal experience in the matter, combined with a knowledge of the effects of selfinduction, mechanical momentum, and magnetic saturation as deduced from theoretical considerations. I do not think that anyone who knows anything of the working of the Tivoli-Rome plant would for a moment hesitate in saying that on a large and important station like that of Niagara Falls parallel working is essential; and this is the opinion of Prof. Mengarini, who has so ably directed the works at Rome.

MOTORS.

Under this section it may be as well to discuss some of the different purposes for which the electric current will be required. With regard to arc and incandescent lighting, if the frequency be high enough, the current can be used directly for this purpose; although most people would prefer that, in the case of arc lighting, the current should be commutated or converted in some manner, so as to give a continuous current. That this is unnecessary, however, is amply proved by the perfect success of the arc lighting by alternating currents in Rome and many other large cities, especially those which have been established by Messrs. Ganz & Co. At the present time, one of the largest applications of electricity in the United States is for street railways, which require a continuous current. Another similar purpose which we shall have to consider is the application to canal boats, since it is intended to work the Erie Canal by electricity. This canal starts from the Niagara River, and reaches the Hudson River at Albany, 350 miles distant. For these purposes some sort of commutator or motor transformer will be desirable. Some of the first work which will be done is the supply of much direct current at 150 volts for the production of aluminum. This also requires the continuous current, and similar means must be used for obtaining it. Among the large class of mills which will be established at Niagara Falls, one of the most important kind is wood pulp mills, one of which is already working on our land, and will be the first to receive water-power from our canal. This type of mill uses many thousands of horse-power, and is worked continuously day and night. In this feature it resembles, probably, a large number of the mills which will take advantage of the cheap power at Niagara Falls. Such mills are working continuously day and night, and do not require to be ever stopped or reversed. This is an important class of work in our case, because current can be supplied to such mills by means of synchronizing alternators whose efficiency is extremely high, and this may, perhaps, be done in some cases without transformers. We require also to consider the case of small motors for use in shops, and for elevators, cranes, and a large number of other purposes. In this type of motor frequent stoppings and reversals are necessary. Hitherto direct-current motors have generally been employed for this latter purpose, but the rotating-phase induction motors are distinctly suitable, and when these have been fully

developed they will probably be largely used for this purpose. The commutated current is a thing which is sure to be in common use before long, and although our arrangements at Niagara Falls are perfectly complete without a machine for this purpose, still its employment has been considered by us, and the probability of its future use has influenced our judgment in some points. There are so many purposes for which the direct current is most convenient, that people would generally accept it for transmission if it were capable of being economically transformed up and down to different pressures. The direct-current dynamo is really an alternating dynamo with a commutator placed upon it. If the commutator, instead of being placed there, be placed in the neighborhood of the motor, we obtain most of the advantages both of the continuous and of the alternating current. This is one of the advantages of having two phases generated by the dynamo, because it is much easier to rectify a two-phase current than a single-phase current, In addition to the motors above specified, there are a large number of single-phase motors which start with a powerful torque which have been invented by different electricians, but which are not yet put upon the market. There are also machines with commutators like a directcurrent dynamo with laminated field. These all become very efficient and useful when the frequency of alternations is sufficiently diminished.

LINE CONSTRUCTION.

A great deal of attention has been given to the different methods by which current can be conveyed to the points of consumption, whether on our own property or at Buffalo, or even further. Naturally the pole line was first dealt with, in which the poles might be constructed of either wood or iron. This is the cheapest type of construction, and has some advantages, but we must consider the climatic conditions in the neighborhood of Niagara Falls. We are subject there to severe thunderstorms, and troubles from lightning have already been serious in several parts of the United States in connection with electrical machinery. Snow and frost are very severe, and sleet forming upon the wires and insulators may cause a great amount of trouble. There are also at times very violent gales sweeping from over Lake Erie. All these difficulties can be counteracted to some extent, but it is nearly certain that with overhead construction occasions would arise when the continuity of operations would be interrupted, and this would be a very serious matter. The next system to be considered in order of cost would be underground cables, but I am strongly opposed to the adoption of these for any considerable length. It is true we are able to deal with their capacity so as to reduce its injurious effects, but surely the best plan of all is to abolish the capacity itself as far as possible. The most satisfactory method of proceeding is to build a subway of sufficient size to enable a person to walk along it and to carry bare copper_conductors in it, but this a matter of considerable expense. I am glad. however, to be able to inform you that the officers of the company resolved last summer that a subway such as I have described should be constructed from the power-house up to the Pittsburgh Reduction Company's works, where aluminum is to be produced, a distance of 2,500ft. In accordance with their instructions I prepared plans, which give space enough to carry the conductors at 20,000 volts for all the power that will be developed by the present tunnel, parallel working being adopted. The subway is built of concrete having a minimum thickness of 10in. The height inside is 5ft. 6in. Wooden beams are embedded in the concrete on both sides every 30ft. When the concrete is set these beams are removed, and iron castings for supporting the brackets that hold the insulators are put in their place, and these are then grouted in. Iron brackets are bolted to these castings, and the oil insulators placed upon them. We shall probably adopt copper strip conductors. The bottom of the subway is always on an incline, and is of curved shape to drain off any water of condensation, but it is also proposed to force air through the subway so as to keep it dry. The 2,500ft. now being completed is all drained at the powerhouse end by a boring into a water-bearing stratum. At the bottom of the subway the concrete is formed in two steps, the lower one of which supports sleepers for a very light tramway upon which a truck can run to carry supplies, and also to carry the inspector. At first this can be moved by a hand lever, but arrangements are made for eventually driving it by electricity, the conductor being carried on the floor, between the stringers (placed on the ties or sleepers), which form a platform running along the length of the subway. On the stringers outside the rails is placed a screen separating, mechanically and electrically, the part of the subway where the conductors are from the part where the inspectors walk. This screen is formed in 10ft. lengths of wood supporting expanded metal, covered over with plaster up to a height of within one foot of the top, the upper part being left open in the form of a network, through which the inspector can look at the conductors and their supports. These screens are held by iron supports fixed by expanding bolts into the concrete, and can easily be removed. The top of the arch is 3ft. below the surface of the ground, so that it will not be affected by frost. According to the last report, it appears that on October 21st 1,590ft. of this subway had been completed; the total length being put down at present is 2,500ft. Each of the iron castings has a wire attached to it

which passes through the concrete, and is soldered to a copper wire running outside the subway along its whole length, and connected to a plate sunk in the water at any suitable points. At every 400ft. cross streets will be made, and at these points there is a manhole. Also at these points, on each side of the subway, four drain pipes, 3in. in diameter, are let in, closed at their outer ends. When the subway is to be tapped for use on the side streets, or for intermediate points, wires can be laid through these pipes. Between Niagara Falls and Buffalo there is very little rock, but the part where the subway has now passed through has been chiefly in rock. This involved blasting out a channel larger than was required. In this case the part of the trench outside of the subway has been built up of stone. In the construction of this subway American Portland cement has been used, and a very suitable sand from the neighborhood, which contains its own gravel. The whole of this work has been done by Mr. Humbert, and up to the date of my last inspection every part was thoroughly and satisfactorily done. This work is of great importance as conveying to the minds of those who intend to use our power some idea of the desire to ensure continuous working.

With regard to the electric pressure that is to be used for distant transmission, this will undoubtedly advance with experience. Some manufacturers in Europe who tendered for the work proposed to adopt 25,000 volts; but we have considered that at present 20,000 volts is not likely to be exceeded by us, and we may work at a lower pressure at the commencement. When it is remembered that the Deptford machines have one terminal connected with the earth, and are working satisfactorily at 10,000 volts, and when it is noticed that, in consequence, our work would be under exactly the same conditions as regards insulation when working at 20,000 volts, it is easy to see that we are not risking anything experimental in our first work.

With regard to the size of conductors, I worked out the economical size at different current densities for the whole distance. In doing this I took the following data:-I took the cost of copper at 121⁄2 cents per lb., and the annual charge on this cost at 5 per cent. I then computed the power loss in the line, and the amount of power which was left available for delivery. I took the value of this power at the distant end of the line as being $15 per horsepower. This is something more than what it costs us to produce it, but when the power available from our tunnel is nearly all consumed this quantity will have to be increased. It must also be remembered that I have not allowed for the increased size of the conductors required by the retardation of phase, which is an unknown quantity. Still, it will be seen that from these considerations we may be able to work economically at a slightly higher current density than is obtained from this investigation. From this work it appears that the most economical density to work at is 350 amperes per square inch. If this density is used the fall in volts between Niagara Falls and the northern boundary of Buffalo is only 32 per cent.—a matter which makes regulation extremely easy.

With regard to the efficiency of the system, it is remarkable how high the efficiency of the dynamos comes out when we are dealing with the large units of 5,000 h. p. There can be but little doubt that the efficiency, electrical and mechanical, of our dynamos may reach at least 98 per cent. Taking off 31⁄2 per cent. for losses on the line, we would have 941⁄2 per cent. delivered electrically at Buffalo if no transformers were required to raise the electric pressure to the full 20,000 volts. In cases at Buffalo, where the power consumed is very large, the motor can be constructed on the same principles as the dynamo; and if in this case it be ever possible to work at the full pressure without a transformer, it is obvious that the total efficiency of the system-that is, the power delivered by the motor to the shaft of the machinery, divided by the power delivered by the shaft of the turbines to the dynamowill be certainly over 90 per cent. As a matter of fact, if we were to use a higher density of current, and were to use step-up transformers at Niagara Falls and step-down transformers at the northern boundary of Buffalo, and other step-down transformers in the town of Buffalo itself, and were to use motors of small power, and consequently of less efficiency, in this case the total efficiency of the plant might be reduced to 80 per cent., or even lower.

I have given these figures not as indicating precisely the lines on which we have determined to work at Buffalo, but because the present paper is intended to embrace the subject of the general distribution of power, and I thought it desirable to lay before you certain facts in this connection in a definite form.

DESCRIPTION OF MACHINERY TO BE USED.

Under this heading I shall deal chiefly with the type of dynamo which has been finally decided upon. It will suffice to say of the turbines that they are each of 5,000 h. p., that they revolve at 250 revolutions per minute, and were designed by Messrs. Faesch and Piccard, of Geneva. All the principal parts of this machinery were constructed by the I. P. Morris Company, of Philadelphia, but the governors of the turbines are of Swiss manufacture, and part of the steel fittings were constructed in France.

With regard to the dynamo, the Cataract Construction Company at first invited many different manufacturers in Europe and America to submit plans. The number of these that were

submitted altogether amounts to 24, some of the manufacturers having taken a great deal of trouble to submit a series of designs, in order to be able to meet different requirements. Many of these designs were extremely good; but it was determined, after estimating the increased cost of using the European designs, owing to the high tariff in America, and owing to transport, to have the machines manufactured in America. Among the designs from American manufacturers there were none which fulfilled all the requirements of the case, and eventually the Cataract Construction Company decided to get out their own designs, and to submit them to the American manufacturers for tender. I had been for some time previously engaged in working out a design which I am confident none of the manufacturers who had sent in designs could say was in any way borrowed from their ideas. We had received suggestions of an external armature with internal revolving fields, and also of external fixed fields and internal revolving armature. We naturally had a preference for a dynamo with a fixed armature, because the coils can be more securely wound, and are not subjected to the mechanical stresses induced by centrifugal force. But all the designs with revolving fields which had been submitted to us contained a weak feature: the field coils were held in by pole faces secured by bolts or keys to the poles, and this seemed an element of weakness when we considered the enormous centrifugal forces to which the machinery would be subjected. At the same time the turbine makers had insisted upon having a certain momentum, or fly-wheel effect, which was not given by the revolving parts of any of the dynamos submitted to us, and it was found that if anyone of these had been accepted it would have been necessary to add to the design a fly-wheel of large dimensions. Centrifugal force was one of the most important matters to be considered, because at 250 revolutions per minute this force assumes considerable magnitude in the large masses with which we had to deal. Moreover, in all the designs which bad been submitted, the magnetic pull between the poles and the iron of the armature assisted the centrifugal force. The principal feature of the design upon which I was working, consisted in having the armature fixed, and inside the machines, with the fields revolving outside; the fields being formed of a ring of iron with the poles projecting radially inwards. One advantage is that we are able to get the full fly-wheel effect that was required by the turbine makers. This requirement was that in the revolving part the sum of the weight in pounds of each part, multiplied by the square of its velocity in feet per second, should equal 1,100,000,000. The design also gives an extremely good mechanical construction for the revolving parts. The iron ring which forms the yoke of the field serves as a support to hold in the pole-pieces and the exciting coils, and no part is held in against centrifugal force by bolts or keys. Moreover, the magnetic pull between the fields and the armature acts in opposition to, and does not assist, the centrifugal force. The armature is fixed, and a large space is available inside it for the workmen to attend to the bearings, and to reach any part of the armature. It is obviously possible to insulate the armature coils for any electric pressure. With a large machine of this kind, the space occupied by insulation has not the same importance in reducing the output of the machine as is the case with machines constructed in the past. In fact, the armature coils can be wound with the same insulating properties as a transformer, and hence the necessity for using a step-up transformer can be avoided.

Starting with this general principle, I first got out designs of a machine at 33 periods per second, in order that I might compare the general appearance of such a machine with those of other types. The next point was to design a machine of as low a frequency as was possible under the limiting conditions as to weight. The revolving parts of the turbine and dynamo, and the shaft connecting them, are supported by a hydraulic piston, and it was the desire of the Cataract Construction Company not to use a thrust bearing of any kind to support the weight, although there is a thrust bearing at the top of the shaft, which simply acts to retain the apparatus in a fixed position in a vertical direction. Owing to this decision, it was necessary to limit the weight of the revolving parts of the dynamo to 80,000 lbs. In getting out the design for the machine it was desirable to select such a form of winding as past experience led one to believe would be most efficient for parallel working, and I judge from past experience that this is best attained by having the number of coils per pole very small. The 33-period machine has only been sketched out with a view of getting at the general dimensions of the machine. It is not suitable for our special purpose, because it is essential that, without taking the dynamo altogether to pieces, we should be able to lift up through the centre of the dynamo any parts of the turbine shaft which may require repair.

It will be seen that from the necessities of the case at Niagara Falls, the dynamo which was required differed in some respects from what would be necessary in may other cases, but it is equally obvious that in any case of so large a transmission of power the conditions must be thoroughly considered beforehand, and the dynamo specially designed for the purpose. At the meeting of the Board of Directors of the Company, in May, 1893, I was instructed, with Dr. Sellers, to get out plans for an alternator of the type which I have described.

I am not able to lay before you now plans of the machine as it

has been finally adjusted by conference between ourselves and the manufacturers. In the plan which we prepared, the frequency was 16 periods per second, there being eight poles. The armature coils are so wound that they might be connected to give either 2,500, 5,000, 10,000 or 20,000 volts, and the coils were limited in numbers so as to give the best assurance of good parallel working. For various reasons we decided eventually to raise the frequency to 25, and to lower the volts to 2,000, without the means of connecting the coils to give a higher pressure; and instead of winding the armature on the conductors in a limited number of coils, to adopt the methods more commonly used in some of the large types of generators. But since in any future work which is done, the dynamo will be required to be modified for the special purpose, a description of the machine is sufficiently representative of the type of machine for our purpose.

LETTERS TO THE EDITOR.

THE SIEMENS & HALSKE CO. NOT ENJOINED.

IN the ENGINEER or Dec. 20 there appears a note to the effect that "the General Electric Co. have secured an injunction against E. G. Bernard, together with the Siemens & Halske Co. and Major Isaac Arnold, commandant at the Watervliet Arsenal, restraining the contractors from proceeding with the erection of the new electric plant, claiming it to be an infringement upon the Edison three-wire system."

I beg to inform you on behalf of the Siemens & Halske Co. that the above statement is an error. The facts of the case are, that the General Electric Co. obtained a temporary injunction against E. G. Bernard, the contractor, for an alleged infringement of the "Feeder and Main Patent." The Siemens & Halske Co. are in no wise concerned, are not a party to the suit, and have nothing whatever to do with the construction of the plant. So far as the said company are concerned, all that they have done is to have sold three Siemens generators to Mr. Bernard. It is assumed that the Siemens & Halske Co. have a right to sell the machines which since 1867 have borne the name of their inventor. GEO. H. BENJAMIN, Atty.

Hand Regulator for Electric Motors, W. D. Packard, Warren, O., 511,157. Filed Dec. 8, 1892.

The invention consists in providing a rheostat with clock work mechanism for controlling the operation of the switch arm, a spring impelled wheel, and an electrically operated stop for limiting the movement of the wheel. Electric Motor, O. F. Conklin, Dayton, O, 511,196. Filed July 6, 1893.

Employs pole pieces inclosing the ends of the field magnet core and having segmental channels in which the armature is adapted to revolve.

Brush Holder for Electric Motors, J. J. Robinson and F. B. Perkins, Toledo, O., 511,214. Filed Feb 6, 1893.

Has for its object especially to guard against the possibility of contact of the metal with the commutator.

Galvanic and Thermo-Electric Batteries :

Electrical Connector, F. G. Curtis, New York, N. Y., 510,898. Filed Feb. 13, 1893.

Relates to means for connecting primary batteries to one another. Method of Adjusting the Joints of Carbon Electrodes, E. B. Cutten, New York, 510,899. Filed March 28, 1893,

The method consists in means for indicating the resistance at the joint and then adjusting the parts until a certain definite resistance is indicated. Electrode for Voltaic Cells, E. B. Cutten, New York, 510,901. Filed May 1, 1893.

Employs a carbon electrode with a glass support, the former being secured to the latter by the material of the support.

Electrode for Voltaic Cells, E. B. Cuiten, New York, 510,902. 1893.

Similar to No. 510,901.

Filed May 1,

Primary Electric Battery, E. Poppowitsch, Brooklyn, N. Y., 511,159. Filed Dec. 28, 1892.

Employs a packing of saw dust, sea salt, sal-ammoniac, bichromate of pot

Miscellaneous :

Apparatus for Electrolytically Producing Soda and Chlorine, E. B. Cutten, New York, N. Y., 510,900. Filed March 30, 1893.

Electric Pump, F. W. Merritt, Duluth, Minn., 510,921. Filed Dec. 2, 1892. Electric Elevator. F. A. Perret, Brooklyn, N. Y., 510,932. Filed Nov. 12, 1892. Employs in addition to the armature circuit and the field circuit, a third circuit including an apparatus controlling the rheostat in the armature circuit; this third circuit being a direct shunt to the brushes of the motor. Label Holder, J. H. Shaffer and E. Horowsky, Allegheny, Pa., 511,167. Filed Dec. 21, 1892.

Rheostat, F. A. Weller, Boston, Mass., 511,259. Filed April 20, 1892.

Relates especially to the arrangement of the rheostat within a small compass, and to the proper ventilation of the coils.

Resistance Box, A. O. Benecke, Newark, N. J., 511,286. Filed Sept. 10, 1892. The combination in a set of resistance coils or bridge of a series of fixed contact plates, a series of resistances respectively interposed between successive contact plates, and circuit connections and means whereby one or more of the intermediate contact plates may be electrically connected with either of the end plates of said series.

Railways and Appliances :

Electric Railway Switch and Crossing, W. W. Hendrix, Bowling Green, Ky., 511,017. Filed Aug. 5, 1892.

Electric Railway Trolley, W. W. Hendrix, Bowling Green, Ky., 511,018. Filed Aug. 5, 1892.

Employs a guard for the trolley wheel consisting of two jaws closing above the wire and adapted to be forced apart by each hanger and to spring back into position after the hanger has been passed.

Electric Railway Trolley, W. W. Hendrix, Bowling Green, Ky., 511,019. Filed Oct. 7, 1892.

A rotatable trolley pole revolving upon a circular track on the roof of the

car.

Electrically Operated Railway Switch, C. A. Stone, Newton, and E. S. Webster, Boston, Mass., 511,173. Filed Aug. 30, 1892.

Closed Conduit Electric Railway, W. S. Smith, Berkeley, Cal., 511,254. Filed Feb. 29, 1892.

Employs junction boxes between the sections of the conductor with ball and socket joints between the conductor and the walls of the boxes. Switches and Cut-Outs :—

Electric Regulating Switch, E. A. Barber, Watertown, N. Y., 511,187. Filed June 26, 1893.

Has for its object to automatically transfer the energy not needed for operating motors on the main line to suitable resistance coils for absorbing the surplus energy.

Electric Switch, J. L. Hinds, Syracuse, N. Y., 511,240. Filed Nov, 27, 1891. A snap switch for incandescent circuits.

Telegraphs :

System of Telegraphy, J. A. Parker, St. Louis, Mo., and L. L. Summers, Chicago, Ill.. 510,929. Filed July 30, 1892.

Relates especially to means for increasing the speed and accuracy of the operation of stenographic transmitters.

Telegraphic Relay, E. Weston, Newark, N. J., 511,005. Filed June 4, 1891. Employs a fixed body of magnetic material disposed in the field of force of the magnet, and a coil of conducting material surrounding the fixed body and supported by pivoted shafts.

Telautograph, R. M. Hunter, Philadelphia, Pa., 511,081. Filed May 26, 1893. Telegraphic Transmitter, H. F. Stine, Dec'd., Red Bud, Ill., 511,172. Filed May 4, 1893.

A stenographic system of telegraphy.

Morse Transmitter, A. F. M. Cornaud, Brussels, Belgium, 511,234. Filed May 29, 1889.

A stenographic telegraph transmitter sending signals by the Morse code. Telegraph Relay, E. P. Medina, San Francisco, Cal., 511,244, Filed May 4,

1891.

MR. H. A. WAGNER, who has for so long been identified with the Missouri Electric Light and Power Company as its superintendent, has, upon the retirement of Mr. James I. Ayer from the Municipal Electric Light Company, assumed the office of general superintendent of this company also. In so doing, Mr. Wagner finds himself responsible for the affairs of two companies, one carrying 110,000 incandescent lamps and the other 4,000 arc lamps. Mr. Wagner also remains as general manager of the Wagner Electric Mfg. Company, and will continue to direct its affairs.

MR. W. J. HAMMER is to marry Miss Alice Maud White on January 3, at the residence of her parents, Mr. and Mrs. T. H. White, 1581 Euclid Avenue, Cleveland, O.

MR. HORATIO A. FOSTER, who is associated with Prof. George Forbes in this country, was married at Chicago on December 22, to Miss Florence Louise, daughter of Mr. and Mrs. Richard Root, of Keokuk, Iowa.

Trade Notes and Novelties

AND MECHANICAL DEPARTMENT.

LUNDELL DIRECT-CURRENT DYNAMOS AND
MOTORS.

THE Lundell type of direct-current dynamos and motors is so simple that an elaborate description of the different parts seems to be unnecessary. The chief characteristics are embodied in the novel construction of the field-magnet, whereby a single energizing coil magnetizes all the pole-pieces and a strong protecting shell for the windings of both field and armature forms the magnetic circuit.

and the resistance of the magnetic circuit reduced to a minimum, whereby a considerable economy in the ampere turns of the energizing coil is effected.

The armature adopted for these machines is of a modern Pacinotti form. This type of armature has in the past been subject to unfavorable criticism on account of the resultant heating of the pole-pieces, but it is now recognized that this heating was not due to the Pacinotti ring itself, but to the lack of knowledge with regard to its proper design. A little reasoning will show that when the ratio of the distance between the teeth and the magnetic gap is too small, a concentration of the lines of force will take place, so that the pole-pieces will be swept over alternately by sections of the highly concentrated lines of force, and by practically inert material. The result is that Foucault currents must inevitably be set up in the pole-pieces and cause the heating, which has been noted in the past. By so proportioning the teeth,

The arrangement of the field-magnet and its energizing coil is clearly illustrated in the accompanying engravings.

It will be noted that the two field-magnet halves when bolted together form a shell which completely protects the armature, the whole of the shell being utilized in the magnetic circuit. These field-magnet halves are so designed that they are readily withdrawn from the mould in casting. The cross-section of the shell equals the cross-section of the base of the pole-pieces, so that no choking of the lines of force can occur at any point. Cast steel is employed for all these dynamos and motors. The single energizing coil not only reduces the construction of the machine to the simplest point, but by having only two terminals it is especially adapted to be placed in the hands of inexperienced users, as it avoids any possible mistake in connecting up or any delay or trouble in examination when such becomes necessary. Another feature of the design is that the pole pieces are magnetized directly,

however, that the lines of force emanating from the pole-pieces are more evenly distributed over their entire surface surrounding the armature, this abrupt demarcation is avoided, with the result that Foucault currents are also avoided in the pole-pieces.

The result of actual practice with the Lundell machine has shown the soundness of this theory, which is carried into practice by the employment of deep and narrow slots.

Notwithstanding the iron clad nature of the machine, the concentric position of the field-coil allows the armature to be withdrawn without disturbing either the field-coil or the pole-pieces.

The openings around the armature at the ends of the fieldmagnets are, in the larger machines, covered with metal screens to protect the working parts, and to secure at the same time perfect ventilation. The commutator portion of the armature alone projects outside the screen, and is well protected by a strong bracket which carries the out-board bearing. The brushes are

end of a brush-holder; while its forward end in the shape of a T presses against the carbon which slides in the ways in the brushholder. To remove the carbon, it is merely necessary to press the spring upwards out of the slot, which releases it so that the T can be withdrawn, and the carbon slides out.

The bearings are constructed with mechanical accuracy, are self-oiling and are provided with a vision gauge. The bushings are made of the best material and are so arranged as to be readily removed and renewed when worn out.

The oiling is accomplished by means of a number of rings which encircle the shaft and dip into the reservoir, thus continually feeding fresh oil to the bearing. In order that the attendant may know the exact condition of the oil, a simple device has been added, consisting of an elbow with an oil-chamber, rising slightly above the normal level of the oil. The vertical arm of this elbow is so arranged that when the visual gauge is half filled the bearing is properly oiled. The glass tube is made so short that by no possible inadvertency can the attendant pour in oil sufficient to flood the bearing and cause the oil to run out at the inner surface of the shaft and so go into the armature.

power plant, it is highly necessary to run a dynamo very close to schedule speed, which can only be determined by an instrument such as the above.

JOHN SCOTT MEDAL AWARDED FOR THE EDSON GAUGE. THE John Scott legacy medal and premium, held in trust by the city of Philadelphia under the legacy of John Scott of Edinburgh, to be used for the encouragement of "ingenious men and women who make useful inventions," provides for the distribution of a medal incribed, "To the most deserving," and money premium in the sum of $20, has just been awarded to Jarvis B. Edson of New York, for his pressure-recording gauge, by the Franklin Institute.

The general adoption of these valuable instruments proves their indispensable nature, for in no other way can a proprietor place himself in a position to know how the steam pressure is carried during night and day, or how much inattention accompanies the firing. As it is a well established fact that carelessness and indifference at the furnace door wastes coal in an amount often

The Interior Conduit & Insulation Co., manufacturers of the Lundell dynamos and motors, claim that their efficiency is as high as can be obtained by any first-class machine.

THE SOUTHERN PACIFIC RAILROAD COMPANY will build a new cotton shed at New Orleans, 120 feet wide and 350 feet long. They bave placed the contract with the Berlin Iron Bridge Company, of East Berlin, Conn. The building will be entirely of iron, the sides being made with the Wilson patent rolling shutters.

sufficient to pay an extra dividend, to say nothing of loss in the cylinder from lack of initial pressure and proper economy from expansion of the steam, for the firemen little understand the necessity for maintaining high initial pressure. "Following" too far or cut-off" too short, are both wasteful of steam and can only be controlled by the fireman carrying uniformly such a pressure on the boilers as the engine requires for the work it has to perform.

It is equally evident that such records, similarly produced, are as valuable where compressed air, water or other fluids are desired to be maintained under prescribed degrees of pressure.