The system of distribution is a solid network of underground conductors on the three-wire system, extending from North avenue to Thirty-ninth street, a distance of six miles north and south, and from Lake Michigan to Blue Island avenue, a distance of one and one-half miles east and west. The entire network is continuous from end to end, and is supplied at present from four central stations, all connected in parallel through the network and each feeding into it. The two large stations located at Harrison street and Washington street on the Chicago River, and known as stations No. 1 and No. 5, respectively, are condensing plants, while the stations on the north side and south side, located at North Clark and Oak streets and Wabash avenue and Twenty-seventh street, known as stations No. 4 and No. 2, respectively, are non-condensing.

The total current furnished to the network at the time of maximum load of the system in the winter of 1897 was 50,730 amperes, and is divided as follows:

The total low-tension, direct-current kilowatt-hours'

output for the stations for the fiscal year of 1897 was 15,255,466, divided as follows:

The pressure at the feeder ends throughout the system is maintained at 115 volts on each side of the

three-wire system. Although the maximum-station pressure is 149 volts, the average pressure of all stations for the year is 126.2 volts, giving an average loss of pressure of 11.2 volts or 8.8 per cent, which means an average yearly efficiency of distribution of

91.2 per cent from the station switchboards to the customer's meter.

The centre of distribution in the business district of the city is at Adams street, between Clark and La Salle streets. Station No. 1, which, as has been shown, furnishes 74.3 per cent of the total lowtension output, is located on the Chicago River at Harrison street, 3,340 feet distant from the centre of distribution at Adams street. Station No. 5, which furnishes fifteen per cent of the total low-tension output, is located on the Chicago River at Washington street, and is 4,500 feet from station No. 1, and 3,000 feet from the Adams street sub-station. These two stations furnish all the low-tension output for the district bounded by the river on the north, Harmon court (approximately) on the south, Lake Michigan on the east and the river on the west. They also furnish all the energy for the entire low-tension system of the city during the hours from midnight until dusk the following afternoon, and a portion of the output of districts No. 2 and No. 4, from dusk until midnight daily; and ultimately they will furnish all of the output of the territories mentioned, and all of the energy required for alternating transmission. lines into the outlying districts of the city and its suburbs.

The load curves "A" here shown, indicate the amperes furnished in district No. 1, by stations No. I and No. 5, the small lower curve representing that delivered by station No. 5, and the lower large curve showing that delivered by station No. 1, and the upper curve curve representing the total amperes delivered to district No. 1.

The distribution of current from these two stations to the underground net work is as follows:

From station No. I to the Adams street substation is laid an immense trunk line known as the Adams street trunk line, having a total crosssectional area of 66,000,000 circular mils, 28,500,000 circular mils being ordinarily connected on the positive and negative sides and 9,000,000 circular mils in the neutral. The length of this trunk line is 3,340 feet, and is made up of fifteen special Edison tubes, each 3,000,000 circular mils area, laid directly in the ground, and fourteen 1,500,000-circularmils stranded rubber-insulated, lead-covered, and juted cables drawn into cement-lined iron ducts. The trunk line, on leaving station No. 1, goes down a shaft sixty feet, thence through a brick tunnel built especially for it in the river bed to the east side, where it rises again in another shaft sixty feet into the tunnel house, where a small switchboard is located. The portion of the trunk line in the shafts and tunnels, which is 430 feet in length, is made up entirely of cables; of these forty-five are 1,000,000circular-mils Siemens jute-insulated and fourteen are 1,500,000-circular-mils General Electric rubber-insulated, leaded, asphalted and iron-armored submarine cables, each supported on iron racks. Where the cables hang vertically in the shaft, the cable is supported by the iron-armored sheathing clasped between iron plates on a heavy cast-iron ring. The copper conductors thus hang in a sort of basket, the strain being distributed throughout the length of the cable. At the tunnel house the forty-five Siemens 1,000,000-circular-mils cables connect with fifteen 3,000,000-circular-mils, single-pole Edison feeder tubes, and, together with the fourteen 1,500,000-circular-mils cables, are mounted on racks in a large subway, into which the duct line enters about two hundred feet