gold piece. There was some excitement and one after another offered to put more to it until I think they got up somewhere in the vicinity of $40 which they offered the man. He said no, that it cost him more than a month's work, and he kept his five dollar gold piece. THE PRESIDENT:-If there are no further remarks on this subject, we will pass on to the next paper on the programme "Elecric Traction, Notes on the Application of Electric Motive Power to Railway Service, with illustrations from the Practice of the Metropolitan Elevated Road of Chicago," by M. H. Gerry, Jr., of Chicago. In the absence of the author, the paper will be read by the Secretary. the American Institute of Electrical Engineers, Eliot, Me., July 27th, 1897: President Crocker in the Chair. ELECTRIC TRACTION. NOTES ON BY M. H. GERRY, JR. In the following paper will be found a brief discussion of some of the more important problems arising in connection with the application of electric motive power to the heavier classes of railway service. A number of tests and diagrams from the Metropolitan Elevated Railroad of Chicago, are introduced by way of illustration. A part of this paper relates especially to the application of electric power to passenger rapid transit on elevated and subur ban roads. The conditions for this service differ somewhat from common railway practice. Regular stops are made at frequent intervals; the distance between stations on elevated roads, for example, averaging about 2000 feet. The interval between trains is small, and the time of stops very short. The traffic is irregular, is heavy at certain hours, and is apt to increase and decrease at a rapid rate. To make the fast running time desired, the speed must increase up to the point where the brakes are applied; thus the maximum of speed is high compared with the mean speed. There is little or no opportunity for maintaining the speed, and the running time depends almost entirely upon the rate of accelerating and retarding of the train. With a given number of stops per mile, the amount of power required will increase very rapidly with the speed beyond a certain point, and the cost per car mile will not furnish a reliable basis of comparison for the motive power of different roads un less the conditions are the same. A slight difference in the average speed, or in distance between stations may cause a considerable change in the amount of power required. There are in operation at the present time several noteworthy examples of the application of electric motive power to the heavier classes of railway service. The most important of these installations are the Lake Street and the Metropolitan Elevated roads of Chicago, the Baltimore Tunnel Line of the Baltimore and Ohio, and the Nantasket and Berlin lines of the New York, New Haven and Hartford Railroad. From the experience gained on these roads, there is no longer a question in regard to the ability of properly designed electric motors to operate trains. of the heaviest weights in service, and at any speed permissible under practical railroad conditions. In the future, matters of efficiency and general utility must determine the desirability of electric power for any particular railway service. Certain operating conditions have a special bearing on the efficiency of this form of motive power; the most important being the frequency of the train service. If traffic is such that a large number of trains must be operated on a division, the electric power will have an advantage in point of economy, over steam locomotives; and if the trains are few, the reverse will be the case. This condition holds good independently of the weight of the trains or of the speed attained. The length of the line is in itself no bar to the successful operation of an electric railway system, as, by using alternating current apparatus, the power stations may be located favorably, and at long distances apart. The distribution of the current to the trains, while it presents many practical difficulties in detail, is not so serious a problem as it was thought to be at one time. Of the three systems of over-head conductor, conduit, and third rail, the last has given the best results, and is advisable wherever the conditions are such that it can be installed. For roads operating on their own right of way, there is really no serious objection to the third rail, and all of the difficulties encountered at crossings, switches and in yards can be overcome by methods already in use on the roads named above, or by other devices that have been proposed. It is not to be expected that all details of such a system are in an entirely satisfactory and final form, but they are practically operative at present and being constantly improved as difficulties develop in service. The experience already gained also justifies the statement that a reliable overhead or conduit system for heavy service can be constructed if the conditions favor the use of such methods. THE METROPOLITAN ELEVATED RAILROAD. This system, now in its second year of operation, is the largest road in existence employing exclusively electric power for a heavy passenger service. The structure has four tracks, from Market street west to Marshfield avenue, at which point three double track lines diverge. The northerly branch divides again near Robey street into two double track branches. From Market street to each of the termina's, the distance is about six miles. (See map, Fig. 1). Current is conveyed to the trains by the third rail system; the trolley rail" being placed 20 inches outside, and 6 inches above the running rail. It is of the common "T" section, bonded with leaf copper bonds, and divided into sections to provide for expansion. The insulation for the third-rail, on all but a small section of the road, consists of hard-wood blocks, mounted on small iron chairs fastened to the ties. On a recent extension an improved form of insulation made of stone-ware has been tried with success. The electric leakage is small at all times. In dry weather it is entirely negligible and in wet weather is never more than a few amperes. It is greatest after a dry season, when the first shower is washing the accumulated iron dust from the insulating blocks. Steel rails are used for feeders, and copper only to make connections. The feeder system is divided into six sections, which are tied together at junction points through circuit breakers placed in the interlocking towers. The rolling stock consists of motor cars, passenger cars and a few coal and flat cars. The motor cars measure 47 feet in length and weigh about 62,000 pounds when loaded to their maximum capacity. They are mounted on rigid bolster locomotive type trucks, having 33-inch steel tired wheels. The truck centers are 33 feet 6 inches apart and the truck wheel base 5 feet 6 inches. One truck of each motor car is equipped with two motors, each nominally rated at 2,000 pounds drawbar pull. The motors are operated by series parallel controllers, situated in the cabs at each end of the car. Rheostats of the packed ribbon type, used in connection with the controllers, are placed underneath the car. A circuit breaker placed in each cab is used both as a safety device and as a main switch for opening the circuit between the trolley device and the controller. A main fuse box is also provided, and placed in one of the cabs as an additional safety device, but experience has shown that failures of the circuit breaker to act are so rare, that the former piece of apparatus might well be omitted. Circuit breakers have proven very satisfactory for this service, as they cost little for maintenance, are reliable as safety devices, and by their quick action reduce to a minimum the damage to apparatus from grounding and short-circuiting. The cars are warmed by electric heaters arranged in three circuits, two of which take about seven amperes each and the remaining circuit about four amperes. All of the heaters are required only in the coldest weather, and are turned on and off by the trainmen. By cutting out all or part of the heaters for |