The same machine can and has frequently been used at various times as a dynamo for electric lights and at other times for a motor; but there are numerous mechanical and electrical modifications essential to obtain the best results in an electric motor. The first use of an electric motor in any of the cotton mills represented in this Association occurred in a thread mill in Newark, where a dynamo was used in 1882 as a motor to run a lot of thread-winding machines.

Electric motors are now used for hundreds of purposes, but this paper will be confined to references to their uses in cotton mills.

Electric motors are frequently proportioned to use low-pressure currents of electricity, like those employed for direct incandescent lighting.

There are many places where motors can be operated by wires from any of the direct incandescent lighting dynamos; but, if the power required for the motor is more than about one-fifth that required to keep the whole number of lamps lighted, the lights will rise and fall in brilliancy, like those in an electric car when the motor starts and stops, the lighting service is unsatisfactory and the life of the lamps diminished.

The problem is one which must be worked out in each case; sometimes, when a small motor is required for use at short intervals during the day, it might be the more economical to use conductors from a large dynamo which is already installed for lighting the mill at other times. If constant service is required from the motor, then a separate generating dynamo is advisable; and it may be said that in the generality of work it is preferable to put in a generator suitable for furnishing the current to the motors.

The principle holds as good in electric apparatus as in all other machinery, - that more satisfactory results are obtained when there is no attempt made to require a more varied service from any machine than it is fully adequate to furnish.

It is generally advisable to use electricity for the transmission of power at a much higher pressure than that found best

suited to incandescent lamps, because there is a great saving in copper for conductors, and a lesser proportion of the electricity absorbed by the resistance of the wires.

The current of five hundred volts' pressure used for the trolley system of street-car propulsion is not capable of inflicting serious injury upon mankind, although frequently fatal to horses. There have been motors suited for use on arc-lighting circuits, but I believe that at the present time there are not any of them on the market.

Before deciding to install an electric power plant for a service outside of what is already fixed by precedent, expense, delays and disappointment may be avoided by deciding how much you are willing to experiment; and, secondly, how much the party doing the work must experiment before the whole installation is in a practical operating condition.

The fact should not be lost sight of that electricity is merely a substitute for other methods of transmission of power. It has its losses at every step in the course, comparable with those of the wear and tear and friction of shafting and belting. Like them, it also costs money, requires attendance, and wears out. It does not in any detail give something for nothing, but the results in comparison with other mechanical means of the transmission of power are merely the addition of a lot of differences. Sometimes these differences are on one side of the account and sometimes on the other.

An installation of motors in one instance may be extremely economical and in another highly expensive, in comparison to ordinary methods of transmission of power.

Electric motors, like water wheels or steam engines, have their highest efficiency at a point near to their full proper load, and on either side their efficiency in the percentage of electricity converted into work is diminished. The practical operation of some motors has been improved by the use of fly-wheels.

In its application for mill service, the most simple uses are those requiring a variable speed and direction, largely on account of causes outside of the electrical conditions in the

construction of such motors. It is especially advantageous for elevators in storehouses or other buildings not requiring power elsewhere. A motor can be attached to any elevator machinery operated by a belt, and the elevator can be managed in the same manner as before, so that the men have nothing either to learn or to forget. The first motor used for operating an elevator in a cotton-mill store-house was placed in that service in 1882, and is in as good working condition to-day. Another use having a larger field is in its application for railways in mill yards and buildings. The Salmon Falls Manufacturing Company has twenty-one hundred feet of track in the mill yard, and is operating a trolley system of cars to move all their cotton, supplies, cloth and coal, with two men, thereby dispensing with the services of a team and three men all of the time, and a fourth man a part of the time. The car makes an average speed of six hundred feet per minute, and is always ready for service whenever the water wheel is running. Other mills use electric railroads from the cloth room to the store-house with even greater reduction in cost of moving the load.

There are two systems of overhead trolley propulsion; the ordinary single overhead wire, with the current returning through the wheels to the rails and thence back through the earth to the dynamo, is the simplest and the only one that has a practical system of switches in the wires overhead. This system contains a serious objection, in the electric sparks constantly occurring in the contact of the wheels with the rails, and liable to ignite any combustible substance there, and therefore could not be safely used inside of mills. For inside use it is necessary to use the double overhead wire system by which the circuit is made between the two wires, without using the rails as conductors. In either case the overhead wires should be thoroughly protected by guard wires whenever there is a possibility of telephone or other wires falling upon them.

Electricity is filling a most useful purpose in operating travelling cranes, and the few store-houses in mills which are provided with travelling cranes use them at such infrequent

intervals that it is probable that hand power is still the cheapest method of operation; but for erecting shops, and other places where constant service is required, electricity affords great advantages for working such cranes.

Motors have been applied to calico-printing machines with great success. The absence of heat, small amount of space, little momentum of the revolving parts, and the control by which the machine can be uniformly moved in either direction at any desired speed, are all advantages of the highest practical value.

Other classes of work require that the motor should revolve at as uniform speed as can be obtained by a water wheel, or better, if possible. Motors will revolve at a constant speed if furnished with a current of uniform pressure. A compound generator will produce a current at a uniform pressure with variations in the load or quantity of current required by the motors; and it will also to some extent compensate for slight variations in the speed at which it is driven. Therefore it may be said that the speed of an electric motor may be more uniform than that of the water wheel or engine from which it derives the power which it gives forth.

A variation in lights is not a direct measure of variation in a dynamo, because a change of one per cent. in the pressure of the electricity in an incandescent lighting system would cause a variation of several per cent. in the amount of light from the incandescent lamps.

The class of service for the distribution of power throughout a mill as a substitute for belt or rope transmission has not been tried in cotton mills, but there are many cases where it has been tried in machine shops and yielded excellent results. The amount of power required in cotton mills is so much greater than in machine shops that the subdivision should be to a smaller unit than a whole room in a large mill.

I am convinced that such a distribution of power is mechanically feasible; but will it pay to do so when motors and generators each cost nearly or quite forty dollars per horse

power, or, including wire and foundations, over one hundred dollars for every horse-power transmitted?

Another class of applications consists in distributing the electricity from a central station in a mill yard to the various buildings.

The most complete plant of this kind is at the Edison Works at Schenectady, where seventeen hundred horse-power is electrically distributed to numerous shops situated at various places on a tract some twenty acres in extent.

The Thomson-Houston Works at Lynn have an extensive electrical distribution of power in their present works, and will have a larger power plant when their new works are completed.

At the Cumberland Mills in Maine two hundred and sixty horse-power is transmitted over a mile by the Mather electric system, arranged by Messrs. Stone & Webster of the Massachusetts Electrical Engineering Company of Boston; and motors are used to drive paper machinery, giving from poorly governed water wheels a sufficiently steady motion for calenders; but the compensation by the compound wound generators is not sufficient to remove the effect of all the variations of speed in the water wheels from appearing in the motors; and these motors cannot run Fourdrinier paper machines, although motors in these mills deriving their power originally from a steam engine perform satisfactory work in driving paper machines. At these same mills an installation of motors is under way for the transmission of twelve hundred to two thousand horse-power for a distance of seven miles.

As water wheels give sufficiently uniform speed for looms, and as motors do give a more uniform speed, there is but little question as to their mechanical suitability for such work.

The third class of applications for electric motors is in connection with long-distance transmission of power, for the purpose of bringing the energy of a water privilege to a locality more convenient for manufacturing.

The problems of short-distance transmission, already con