power at all times to the load, the dynamos running much of the time either over-loaded or under-loaded, which, of course, means a sacrifice of economy. In addition to the variation in load shown by the curve, there is a momentary fluctuation, due to the starting and stopping of cars, the violence of which decreases with the number of cars in service. It is proposed to remedy this variation and operate the dynamos under a steady load by means of a storage battery plant connected in parallel with the line, charged from the dynamos during the period of light load, and discharged into the line on the heavy call for power. The operation of the plant under these conditions is indicated in Fig. 1. Installations of this sort have been placed in several of the large electric light plants, where they are operating with marked success, and there is no reason why they should not meet with the same degree of success in electric railway plants. By means of this auxiliary plant, the proper number of dynamos are run throughout the entire day at their full capacity, and hence at their highest efficiency, the battery taking care of all eccentricities in the load; charging when the load is less than the capacity of the dynamos, and discharging when the load exceeds this. The steam plant may be shut down entirely during part of the night, leaving the battery to operate the road, and in case of a breakdown, the battery may be used to take care of the entire road for a short time. The battery is discharged through a booster dynamo, which is so designed that the compounding of the dynamos and the battery are the same. This arrangement is entirely automatic, so that no hand regulation is required. The efficiency of a battery operating under conditions of this kind will be guaranteed by the manufacturers to be greater than 75 per cent., and a maintenance of 6 per cent. per year on the first cost of the battery will be guaranteed. The great drawback to this system of operation is the large first cost of the battery, which is about one hundred dollars per horse power capacity, figured on a two-hour discharge rate. A storage battery plant may also be used to increase the capacity of an existing power house, and thus save the necessity of adding more machinery. There is another use to which a storage battery plant may be put, which will, perhaps, appeal more strongly to the street railroad man. This is to install it as a sub-station to maintain the voltage at the ends of long feeders, which are subject to fluctuating loads. In this case the batteries are charged from the distant power house and discharged into the trolley wire. The feeders from the power house to the storage batteries are figured only for the average load, instead of the maximum load, as would be necessary in case the line is fed directly from the power house. The economy in this installation depends very largely upon the difference in cost between the feeders in the two cases. Besides the question of economy, however, the sub-station will give the better service, as the voltage will not fall and rise with the fluctuations of the load.

A number of power houses operating long lines are now equipped either with boosters or high voltage dynamos. Long lines usually have

a booster constantly in circuit. This machine is automatic in its action, and raises the voltage with every increase in the load. Some power houses operate a high voltage dynamo for use on sections which are subject to excessive loads. The feeder boards in this case are equipped with an extra bus bar, so that any section may be thrown on the high voltage machine.

While each individual engineer has his own ideas concerning power house construction, and while each road building a power house may purchase a different apparatus, there is one general design which has been followed in many of the plants recently installed. It has been adopted by so many different engineers and in so many different places that it might almost be called the Modern Power House. The general features of this design are shown in Fig. 2.

The engine room and boiler room are divided by a brick wall and under different roofs; both are brick buildings, covered with an iron truss roof; the boiler room is set on the grade of the street, and the engine room from ten to twelve feet above this grade, the space below the engine room being utilized for the piping and condensers. The engine and boilers are set at right angles to the wall between them, with the engines next to the boiler room, so that the piping is made as short as possible and the condensation lessened. The switch board and feeder board are set on the opposite side of the room from the boiler room, so that the length of the dynamo cables is equalized as much as possible. The general features of this design may be summed up as follows: It is compact, to save real estate and buildings, and to minimize the number of employes and the superintendence. Large units are used for the sake of economy and to save the number of working parts. The building is, as far as possible, fireproof.

The electric part of the problem has been solved, temporarily at least, by the adoption of the multipolar, direct coupled dynamo. The large, slow speed engine has followed as a necessary consequence, and the general direction of improvement in power house construction seems to be toward the use of devices to prevent the waste of heat and to minimize the labor required.

There can be no more appropriate place to quote the proverb that cleanliness is next to godliness. An engine and dynamo room should be kept scrupulously clean. This is especially true in regard to the electrical devices, as a very small amount of grease and dirt in the wrong place will cause serious damage. Beyond the mere æsthetic consideration that cleanliness improves the looks of things, there is also the fact that a thorough cleaning amounts to a rigid inspection, and small leaks and defects are often discovered in this way which might otherwise pass unnoticed until they had become serious matters. It is to be regreted that this advice is not more generally followed, as there is more lost through dirty and greasy electrical devices, badly set valves, leaky steam joints, poor firing and careless supervision, than ever will be gained through the use of compound, condensing engines.

As a means of comparing different kinds of machinery, figures as to cost of operation have been collected from some of the large modern power houses, and their comparison reinforces what has just been stated, that less depends upon the refinements of the machinery, than upon the condition in which the apparatus is kept, and upon the supervision to which it is subjected. Among those having the lowest cost of operation was a power house, equipped with direct coupled generators, but operating single cylinder, non-condensing engines, burning soft coal and using hand firing, while among those having the highest cost of operation are several power houses supplied with compound condensing engines, and burning anthracite coal. The lowest results are about three-quarters of a cent per K. W. hour, some records running slightly below this, while the results from some of the large

stations are as high as one and a quarter cent per K. W. hour. These figures include the cost of coal, water, supplies, repairs and all labor, but do not include anything for taxes, insurance, interest or depreciation. The cost of operation depends largely upon the cost of coal, and upon the relation of the average load to the total capacity of the power house; the higher this ratio, the less being the cost of operation.

The modern electric railway power house, although it has been developed entirely within the past ten years, represents the thought and the experience of many men. It has been developed carefully, detail by detail, until it is now a work both of reliability and efficiency. No one man and no one company can claim the credit for this achievement, but no class of men hold a stronger claim to recognition than the managers and owners of street railroad properties, who have ever been ready to encourage with their patronage each improvement, who have freely distributed the information gained by their experience, and who, even in the most radical departures, have ever acted with the courage of their convictions. (Applause.)

Respectfully submitted,

RICHARD MCCULLOCH.

PRIVILEGES OF THE FLOOR EXTENDED TO MR. SEIRYO MINE, ELECTRICAL ENGINEER OF THE JAPANESE

GOVERNMENT.

Mr. H. H. Littell, Buffalo: Before action is taken upon the excellent paper which has just been read, I move you, Mr. President, that the privileges of the floor be granted to Mr. Seiryo Mine, Electrical Engineer of the Japanese Government, who is present at our meeting. Carried.

Mr. Baumhoff, St. Louis: I move you, sir, that the paper just read by Mr. Richard McCulloch be received and spread upon the minutes, that a vote of thanks be extended to Mr. McCulloch, and that advance sheets of that paper and all other papers read before the Association be sent by the Secretary to the various member-companies. Carried.

The President: It is now in order to discuss the valuable paper just read by Mr. McCulloch on the Modern Power House. Is there any gentleman who desires to ask any questions or make any remarks regarding the subject?

Mr. Rossiter, Brooklyn: I ask if any of the members have had occasion to use the storage battery; and if so, with what success?

The President: Has any gentleman present had any experience with storage batteries?

Mr. Richard McCulloch: There is one installed somewhere in Pennsylvania, and the Union Traction Company, of Philadelphia, have one installed at the end of one of their long lines for the purpose of regulating the voltage at that point; but there is a storage battery in operation in parallel with the dynamos, I think at Easton, Penn.

Mr. Bean: I see Mr. B. J. Arnold, of Chicago, is here. He is considered a competent authority on storage batteries. I would like to hear from him. He represents some road

which is a member.

REMARKS OF MR. B. J. ARNOLD ON STORAGE BATTERIES.

Mr. Arnold, Chicago: I had not expected to say anything before this Convention, but the subject of storage batteries has come up, and as I have had considerable experience with them, I will venture to answer the gentleman's question. Before answering the question I beg to express my appreciation of the very exhaustive and excellent paper we have just listened to. I think Mr. McCulloch has gone into the questions which enter into the construction of a power house more completely than I have ever heard them. entered into before, and his conclusions seem to be in almost every instance as nearly correct as we can get them with our present knowledge of power house construction. Certainly, St. Louis has all the conditions necessary for obtaining information on power house construction, and the paper shows the use of these conditions and careful preparation.

In regard to storage batteries, during the last year I have had installed in the Chicago Board of Trade plant, as the consulting engineer for that corporation, a better auxiliary. In my opinion the work of the plant is more severe, if anything, than electric railroad work, because it operates electric elevators in conjunction with constant potential arc and incandescent lights. The elevators take a starting current, varying from o to 800 amperes, and back again almost instantly, corresponding in abruptness to the load on an