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30 water in that end of the area enclosed. Two 6-in. reciprocating pumps in this end of the channel cut are capable of removing the water from the latter. Two centrifugal pumps, one a 12-in. and the other a double section 18-in. are installed in a pump house on the downstream main cofferdam to pump the water from that end of the work. Two reciprocating pumps, an 8-in. and a 12-in; are placed in a house on the edge of the channel cut, about midway between the main cofferdams, and pump from the cut into a flume leading to ome Of the berm ditches: A 12-in. centrifugal pump in a house on the op- posite side of the channel near this point is also used while +the snow is melting, and during heavy rains. The water in the downstream end of the channel cut is removed by three 8-in. reciprocating pumps. ° General Features of Construction: Plant--The controlling feature of ihe extensive construction plant which has been installed by Messrs. Grant, Smith & Co., is the adaptability and arrange- ment of the various parts of this plant to be operated day and night, six days a week, throughout the year. The long and extremely cold winters of the lo- cality in which the work is being car- ried on required unusually careful pre- cautions in the choice of the equip- ment to be installed. At the same time, the continued low temperature of the long winters, the large amount of snow- fall which occurs and the great. quanti- ty of ice that forms in a work of this character interfered seriously with the progress of the construction. In fact, it is believed that the cost of handling work during the winter months has been 25 per cent greater than it is during the remainder of 'the year. An idea of the climatic conditions in this locality may be obtained from the records of the station of the United States Weather Bureau at Sault Ste. Marie. The mean average temperature throughout the year for a long series of years, as given by those records was 39° Fahr. During four months of the year, Dec, Jan, Feb. and March, the average monthly temperature for the same series of years was considerably below 32° Fahr., with frequent tem- peratures as low as 25° below zero, Fahr. Ice forms on. open water six months in the average year, reaching a thickness of 30 in, or more during the winter. Added to these conditions some snow falls nearly every day in the winter and the annual snowfall is quite heavy, the ground generally being 'covered with from two or three ft. of snow during the winter. Notwith- standing these extreme climatic condi- tions the construction work has been THE Marine REVIEW ; | handled day and night, practically with- out interruption, except for Sundays, since its inception. During 1906 the government engineers credited the con- tractor with 290 working days and nights, without . including seven holi- days on which work was in progress. This record does. not mean, either, that part of a.day was counted as a full one, because all of the men are pro- vided with rubber clothing, so work is rarely stopped by rain or snow, the rock bottom of the cut always provid- ing a good working foundation. The various equipment and plant connected with the work is operated, with a few exceptions, on. air fur- nished from a central compressor plant. Air-driven rock drills are em- ployed in making the large number of blast holes in which the channel eut is excavated... The loosened rock is loaded into large skips by steam shovels, the skips being hoisted* out of thé cut, conveyed to spoil banks along the side of the channel and dumped in these banks by long-span cableways with traveling head and tail towers. ._ All of this equipment was selected largely on account of its adaptability to work continuously un- der the trying climatic conditions, which become particularly strenuous at night during the winter. Compressor Plant---The. equipment in the central compressor plant is as complete as that in most" per- immanent: plants. of this... kind, ' and was installed with as "great care. ime plant may, -in. fact, be - con- sidered a permanent one, since it has been operated continuously for over three years. It is in a tight frame build- ing, 40 x 108 ft. in: plan, - which is divided by a transverse partition wall into a boiler room. and an. engine room. The boilet room contains: thtee 200 FH. P. Erie City. sectional water-tube boilers placed in brick settings on concrete footings. These boilers are operated at 150 lbs. pres- sure and are each served by an 80-ft. stack. They are supplied with feed- water by either of two Snow boiler- feed pumps, which draw from a Kel- ly-Berryman feed-water heater. This heater operates on. exhaust steam from the auxiliary units in the plant. The engine room contains two cross-compound two-stage Rand com- pressors; one of these has 40 and 23- in. air cylinders and a 48-in. stroke, producing a capacity of 4,527 cu. ft. of free air a minute at 90 Ibs. pres- sure? the otter machine has 17. and 30-in. air cylinders and a 30-in. stroke and produces 1,900 cu. ft. of free air a minute at 90 lbs. pressure. The largest compressor is. driven by a cross-compound 700 H. P. Newburg Corliss engine, and the smaller one by a cross-compound 325 H. P. Ham- ilton Corliss engine. These engines are operated condensing, each of them being equipped with a Dean jet condenser. Circulating water for the condensers is supplied by any one of three pumps in the basement of the engine room. These pumps also sup- ply water to the feed-water heater from the condenser hot well, or from the river. All of the various units in the~ plant are on heavy concrete founda- tions, which were built with special care. The bed 'plates of the two main units are placed directly on the concrete, without any cap stones. No' trouble from vibration of the en- gines or compressors has ever been experienced, however, although both compressors are in service 23 hours a day for at least six days a week. The compressors deliver to an air receiver, 4 ft. in diameter and 18 ft. long, just outside the building; from which air is piped to various parts of the work. An 8-in. pipe line, 6,000 ft. in length, extends along the. main- land bank of the river, and is con- tinued an additional 2,000 ft. as a 6- in. line. This 8,000-ft. line is pro- vided with several L-shaped vertical joints to provide for expansion and contraction. The line is also laid to drain to drip cocks placed -at con- venient intervals, in order that the condensation may be removed read- ily. A second receiver of the same size as the first is placed on the 8-in. line 3,650 ft. from the compressor plant, to provide for sudden demands for air. Taps are made in the main line so branches, can be carried to the various plants at any point along the work. A 6-in. main line is also 'laid to opposite side of the work to. de- liver air to the engines of two cable- ways on that side. In all, 35,000 ft. of pipe is required to convey air from the central plant to the different parts of the work. This large amount of pipe is entirely exposed to the weather, but the whole air distributing system has been operated during the coldest weath- er. Reheaters have to be used on all air-consuming units, however, and in the winter fires are maintained at dif- ferent points along the supply line to prevent the water of condensation. from freezing and stopping the pipes. Rock Excavating and Handling.--The depth of the rock cutting varies from nothing at each end of the 8,600-ft. cut to as much as 27 ft. at the middle of the latter, with an average depth of 15 to 16 ft. The rock has mostly all been taken out in two lifts, the faces being