rails were placed upon insulating supports between the running tracks. The foot-walk for the convenience of trackmen, was placed above them, so that to the casual observer nothing was apparent but the ordinary contact rail.

The value of an ordinary commercial steel rail as an electric conductor, as compared with copper, is about 10 or 12 to I, with of course the additional disadvantage against the rail of the necessity of the frequent bonding, the rails usually coming in 30-foot lengths. To offset this lower carrying capacity, however, compare rails at $17 per ton with copper at $360 per ton, and it can be seen that one can afford to put in the larger amount of steel required for a given electrical capacity and still have a good margin in favor of the rails. With the present price of rails, however, this argument would not hold true. The rails referred to as "seconds" are rails that have been rejected on inspection on account of some defect which makes them unfit for track work, and yet leaves them perfectly good for electric conductors where no mechanical strain is put upon them. A commercial 80-pound track rail has a carrying capacity about equal to an 800,000 c. m. copper cable. In purchasing the contact rails for the extension of the Douglas Park line, they were made of steel of a special chemical composition, having a higher electrical carrying capacity than the ordinary commercial steel

rail. The composition was obtained after a series of experiments conducted for the Manhattan Railway in New York City, with a view to getting the best possible conductor with a composition of steel that could be successfully rolled into rails. The use of this composition results in a steel rail so soft as to be unfit for ordinary railway service, but the conductivity is raised so that, compared with copper, the ratio is about 8 to 1, as against 12 to I for ordinary commercial steel rails.

Experience has shown on the Metropolitan Elevated system, that with feeders composed of steel rails they can carry enormous overloads without danger from heating; but there are some necessary repairs and inspection of the bonded joints, which would be avoided by the use of copper cables.

On the Northwestern Elevated, in Chicago, aluminum cables have been used at a considerable saving in the original outlay, as this material costs for an equal carrying capacity about 30 per cent less than copper, the relative value as conductors for equal cross-sectional areas being in proportion about 63 to 100 for copper. There are two difficulties which have developed in the use of aluminum cables, one being the fact that the relative expansion with changes of temperature is very great, so that a cable pulled taut in cold weather will have an immense amount of slack with a rise in tempera

The commercial rail gave a resistance of 18.2 microhms per cubic centimeter, or a ratio to copper of 10 to 17. The Albany & Hudson gave a resistance of 12.9 microhms per cubic centimeter, and has about 7.25 times the resistance of commercial copper.

One of the most difficult problems in equipping an electric railway system is the proportioning of the total capacity of a power house to the number of cars run, and the subdivision of this total capacity into proper-sized units. In order to determine these points, it is necessary to be able to estimate the maximum loads that will have to be carried during the rush hours, and the minimum loads during midday and midnight. The maximum load does not always depend upon

or vice versa. On other systems, travel is more equal. Again, the distance between stations, grades over which trains must be operated, and the running time that will be required in order to meet competition with other lines, all enter into this problem.

The question of heating cars is a more serious item than is generally realized, if this is to be done electrically. In extreme weather, when all the heater circuits in a car are thrown on, it takes forty per cent of the total current required for the train, for the heating. The average amount of current used for heating from November to May, however, is only about twenty per cent of the total used in train operations. In subdividing the total capacity of a power house, it is desirable to have a single unit which will carry the minimum light load with reasonable economy, and if the subdivision of the total capacity of the power house into units of this size does not give too large a number of engines, such an arrangement will be found most convenient for repairs, as various parts will be interchangeable.

The load on a power house operating in connection with an elevated railway system, such as in Chicago, varies not

ber of trains are in service. Under the worst conditions, this rate will vary from 300 amperes to 4,000 in fifteen seconds, or the reverse. It is necessary, therefore, that all parts of the engine should be especially heavy, particularly the fly wheel, in order that sudden changes in the load should not interfere with the proper regulation of the engine speed. To take up such violent fluctuations, storage batteries are sometimes used, as on the South Side road.

The accompanying diagram, Fig. 1, shows a typical load curve at the power house. Curve A is that of the trains in service. Curve B shows the additional amount of energy for heating the cars, with heaters only partly turned on during the rush hours; while curve C gives the total load with heaters turned on full during the rush hours. The high peaks of the curve occur at the rush hours of travel.

ample of heavy high-speed electric railway work to be found in the world. Between Wheaton and Elgin, and between Wheaton and Aurora the country is without any large villages, though it is a thickly settled and productive farming country all the way. The syndicate controlling this company has also acquired control of the electric lines connecting Aurora, Batavia, Geneva, St. Charles, Elgin, and Carpentersville.

The chief interest on the road to the electric railway engineer, however, aside from the local situation, is the solidity of the construction, and the high speed at which trains are operated in this service. The motor equipment is designed and guaranteed to maintain a car at a maximum speed of seventy miles per hour on the level at normal voltage on the third rail. To insure this high speed, the motor equipment is the heaviest yet put on cars for this class of service. Each car has

and renders it possible to attain a high maximum speed. From Chicago to Wheaton the line is double-tracked. From Wheaton to Elgin and to Aurora single-track lines are built. However, on the single track, the sidings are of considerable length to avoid loss of time at the passing points.

The road uses the third rail, except in the towns of Elgin and Aurora, where it does not run over a private right of way.

third rail, which is not normally sectioned, but the parts of which are tied together, so that the sub-stations assist each other. The power house is at Batavia, on the Fox river. From the power house, three three-phase three-phase 26,000-volt aluminum feed lines run out, with the arrangement such as to give duplicate feed lines to most of the road. One line runs directly from the power house to sub-station I, at Aurora; from there to

sub-station 2, at Warrenville; and thence to sub-stations 3 and 4, on the main line. Another line runs directly from the power house to the Warrenville sub-station, where it joins the high-tension line from Aurora. Another high-tension line running directly from the power house to sub-station 5, also runs northwest to feed sub-station 6, and continues east to substations 3 and 4. Sub-stations 3 and 4 are therefore supplied from two hightension lines, one of which comes from the power house by way of sub-station. 5 and one by way of sub-station 2. The high-tension lines, therefore, practically form two loops, so that in case of a break anywhere on these lines, current can be supplied from the other direction, except in case of sub-station 6, which for the present has only one source of supply. The high-tension lines are carried on poles, 35 feet to 40 feet high, in the country, and 50 feet to 60 feet high in the towns through which the road passes. About a year ago a French engineer visited Chicago, on a tour of investigation of the rapid-transit systems of this country. He was taken one evening, during the rush hours, to the junction of Fifth avenue and Van Buren street on the Union Loop, and was astonished at the rapidity and frequency of the train movements. He could not believe that this

could be the normal daily condition. He stated that in Paris the law forbade his railway company from operating its trains at less than three-minute intervals, and these intervals were maintained by means of block signals. His road was a third-rail system running on a fenced. right of way on the surface, and extended out through one of the suburbs much as the Lake Street Elevated goes through Oak Park.

To give some facts as to what is actually being done daily on the Union Elevated Loop, let me state as follows:

During the month of January, 1903, 1,523 trains were handled every 24 hours on the Union Loop; or, in other words, one train every 56 seconds on an average during the 24 hours.

During the rush hours from 5 to 7 P. M., 212 trains are handled, or one train every 33 seconds.

During the fifteen minutes from 6:00 to 6:15 P. M., 46 trains are handled, or one train every 192 seconds.

During fifteen minutes in the A. M. rush, 54 trains are handled, or one every 161⁄2 seconds.

During one hour in the A. M. rush, we are handling 187 trains through this crossing, or one every 19 seconds

We are loading on the Union Loop on an ordinary week day, 54,000 people from 5:00 to 7:00 P. M., and 40,000 from 5:15 to 6:15 P. M.

To give an idea of the wear on the various frogs and crossings, there are 27,880 wheels passing through this junction every 24 hours.