diameter, and are designed to withstand full reservoir pressure with a generous allowance for deterioration by corrosion. The inlets are of the bell-mouth type and are protected by trash racks built up of % by 6 inch trash bars on 6-inch centers. At the downstream face of the dam, where the stresses are high, to compensate for the space taken up by the conduits, the concrete is heavily reinforced with T-rails.

The emergency gates are embedded in concrete at the downstream face of the dam, and the needle valves are attached directly to the downstream frames of the gates. The needle valves are 60-inch valves of the internal differential needle type, to operate under a maximum head from the center line of the outlet to the outlet to the maximum reservoir water surface of 163.5 feet. A mast jib crane is provided for handling the heavy parts of valves during installation and operation. The emergency gates are 5 by 5 feet in size, designed for an operating head of 162 feet, with cast-steel gate leaf and 21-inch hoist cylinder. There is no electric power available, and the triplex pump used for operating the gates is driven by a gasoline engine.

STONY GORGE DAM

The outlet works at Stony Gorge Dam are shown in the accompanying illustration. This design is inserted principally to illustrate a different application, covering installation in a dam of the buttressed type with face slab of reinforced concrete.

The outlet consists of two 321⁄2 by 32 feet high-pressure emergency gates, designed for a head of 140 feet, with a 12-inch hoist cylinder, to operate under a head of 98 feet, embedded in mass concrete at the water face of the dam.

Regulation of the discharge is by two 42-inch balanced valves similar to those used at McKay Dam, connected to the emergency gates by 50-inch riveted plate steel pipes. The emergency gates are operated by a direct motor-driven triplex pump. Power for operating the pump and gate hoists, and for lights, is

furnished by a small hydraulic turbine and 25-kilowatt generator, with a 125-volt storage battery for stand-by service.

OWYHEE DAM

There are three sets of high-pressure outlets in Owyhee dam, as shown in the sections of the dam in the illustration on page 86.

Power outlet. The power outlet, at elevation 2,569.83, operating under 100-foot head, consists of two 5 by 6 foot high-pressure gates, properly protected by a trash rack, with 72-inch circular cast-iron conduits extending through the dam and terminating in a tunnel in the rock below. These outlets are for future power development, and when the power plant is constructed the 72-inch conduits will be extended to the turbines. Regulating outlet. The regulating outlet, shown in the illustration on page 89, is at elevation 2,469.83, operating under 200-foot head, and consists of three 4 by 4 foot gates, designed for 250-feet head, with 18inch hoist cylinders, embedded in the dam near the water face, with three 48-inch internal differential needle valves installed in a reinforced structure on the downstream face of the dam. The valves are connected to the gates by 57-inch cast-iron conduits designed to withstand full reservoir head, with a liberal allowance for deterioration. The valve house is provided with a massive curved concrete roof for protection in case water should overtop the dam.

Sluicing outlet.-The sluicing outlet is at elevation 2,370, with the gates installed under 300-feet head, but the hoist cylinders provide capacity for operation under only 125-foot head. The layout of this outlet is shown in the illustration on page 88. Because of the unusually high head under which these gates are installed, and the fact that the lower 250 feet of water in the reservoir is dead storage, it was considered advisable to install the gates, 4 by 5 feet in size, in tandem, using the upper gates for protection of the lower, or service gates. The conduits below the gates are 60inch cast-iron pipes.

IT

T IS a continuous performance, this work at Arrowrock, and although you will be told that the active work is carried on only between 8 a. m. and 2.45 the following morning, leaving 54 hours of "inactivity" out of the 24-still it looks active enough to the layman who may venture out at those early morning hours, for there is work going on everywhere, active work too, apparently, in spite of our information that the work has "stopped" at a quarter to 3 in the morning. And it certainly sounds active when the locomotive starts out at 5.45 and makes up its train of empties for the first trip on the gravel haul; and again at 7 o'clock when the "grave-yard" shift shoots the holes that it has been drilling all night.

We find, though, after we have asked more questions, that the word "work" as used by the initiated means only certain very definite things like excavation or placing concrete-something that actually adds directly to the progress on the dam, and that cooking daily meals for 900 hungry men, coaling locomotives and steam shovels with their daily supply of fuel, pumping the seepage water from a hole 80 feet below river level and nearly an acre in area, operating a standard gage railroad running nine trains per day, keeping in repair cableways, engines, cars, derricks, hoists, electric motors, concrete mixers and all the other machinery and equipment necessary to build these enormous structures—these things are only incidentals, and are not "work" at all in the strict sense of the term, although some of the most valuable men on the pay roll are thus engaged.

At 8 o'clock, then, the "work" starts. And before the whistle has quit blowing its one short blast, the concrete mixers have started and the concrete gangs on the dam have already begun to scrub in the cement wash on the hardened surface, so that a good bond will be made with the fresh concrete. Every man has been at his post, waiting impatiently for the signal, for yesterday, the reports says, the night shift placed 1,260 yards, and the only way to beat that record is to make every second count. The old time system of driving the men with noisy, blustering foremen seems to have passed. The spirit of rivalry is a much more wholesome and effective spur, and no wonder that estimates of cost and of progress are being cut, when every man from foreman to water boy is interested constantly

in beating the other fellow's gait. A trainload of sand and gravel has already been brought from the gravel pit 13 miles away, so the mixer bins are full and the mixers start off with a good supply to draw from.

They are wonderful machines, those double cone affairs, turning constantly, mixing and kneading their 2-ton charge of concrete, dumping with the regularity of a clock, a batch every minute, and right back for another charge, but always turning with never a stop until the noon whistle blows. There are electric cars that take the concrete from the mixers into a tunnel to the distributing tower, gliding back and forth like mice, stopping only long enough to get their load at one end of the trip and dump it at the other. The cableway buckets sailing through the air between the tower and the hopper where they leave their load, remind one of huge birds-never in a hurry, but always on the move. They take the concrete from the cars to the hopper, from which it is distributed by chute to whatever point may be desired. In less than three minutes from the time the gravel leaves its bin at the mixing plant, it has found its final resting place in the concrete of the dam.

This performance goes on, without interruption, for 16 hours every week day, three mixers, three electric cars and three cableways, all working together with surprising regularity, with the result that every day the dam is more than 2,000 cubic yards nearer completion. If the amount of concrete placed in one day instead of being spread in layers on the dam, were placed in a monument 10 feet square, it would reach to a height of more than 600 feet, and in one month, this monument would be nearly 3 miles high.

Every two hours a train arrives from the gravel pit with 15 or 16 cars of sand and gravel. Every day 10 to 12 carloads of sand-cement are manufactured at the sand-cement plant. This is not loaded into cars, however, but is stored in large covered bins, and is blown. over to the mixing plant, as needed, a distance of about 700 feet, through 3-inch pipes, by compressed air.

On the steep cliffs at either end of the dam, gangs of men are busy cleaning off the loose and soft rock, cutting keyways and preparing the abutments to receive the concrete of the dam as it is built up against them.

There seem to be carpenters everywhere-setting up panels on the face of the dam, to hold the fresh con

crete in place until it has hardened sufficiently to stand by itself, building bulkheads here and there, erecting forms for the outlets, where the discharge from the reservoir will be controlled, building stagings and trestles, extending steps and ladders as the different sections of the dam get higher and higher.

Up on the spillway they are cleaning down the slopes of the immense trench that was dug by the steam shovel through solid rock. Nearly 200 feet high, these

at one sitting, and this is only one of the nine meals served during the day-and night.

From 1 o'clock till 5, the operations go on as before, and word is passed to the night shift that they have a record of 1,268 yards to beat.

Another meal at 5.30 and the day shift is through, but at 6 o'clock the night shift, who had their "breakfast" at 4.30 p. m. starts in with as much enthusiasm to break another record as if it were the special personal

slopes are, on the uphill side, and the men working there barely get a foothold and are held from falling by ropes let down from the top. Dangerous work, this, but it has to be done. All loose rock must be cleaned down before it will be safe to work below, where the concrete lining is to be laid, to make a smooth waterway for the overflow from the reservoir.

Before we have any more than gotten over the job, a whistle blows, and except for a stray batch of concrete caught in transit, that must be placed before it sets, everything stops. All roads now lead to the messhouse, and from every conceivable direction they swarm to that goal. At this meal more than 400 men are fed

affair of each of them. For awhile it looks like a repetition of the morning's performance, and we were just concluding to drop in at the club house for the semiweekly picture show, when the lights began to come on, and the whole aspect of the work was changed. Powerful searchlights were thrown on the cableways, lighting them up clear across the canyon; other searchlights were spotted on the hoppers where the concrete buckets dumped. Arc lights were pulled out over the work on cables stretched overhead. Clusters of incandescents, with an arc here and there, lighted up the railway. There were no dark corners within the limits of activity, and then we understood why it is