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ever being washed away. Its floor and side walls of concrete are securely anchored into this rock hill. The spillway of the dam will have its solid crest at an elevation of 69 feet, but piers 8 feet wide were built on top of the crest and grooved for gates which will close the openings and complete the upper portion of

the dam.

When the spillway gates are raised to the full height, they will permit a passage of 140,000 cubic feet of water per second. This water will pass through a diversion channel into the old bed of the Chagres and flow out to sea. About 250,000 cubic feet of concrete have been used in the construction of the spillway. Below it will be placed the great power plant containing the turbines which, run by the water coming from the overflow of the dam, will provide all the electricity and power required for the entire canal.

Gatun Lake itself with its surface 85 feet above sea level will be a beautiful inland basin of fresh water covering an area of 164 square miles and containing 206,000,000,000 cubic feet of water! Draining a watershed comprising 1,320 square miles, it will be dotted with numerous islands and surrounded by rolling hills, which will provide a picturesque passage for steamers passing from ocean to ocean. Being of fresh water, it will serve to clean the bottoms of vessels befouled by long journeys through salt

water.

The chief source of supply for the water of Gatun Lake is the famous Chagres River, whose old bed crossed the canal 31 miles from the Atlantic entrance and 23 miles from the Gatun Dam, flowing from the northeast to the canal, which it struck nearly at right angles and then took its course almost due northwest to the point where it empties into the Atlantic Ocean. During 8 or 9 months of the year the lake will be kept constantly filled to its capacity and, consequently, a surplus will need to be stored for only 3 or 4 months of the dry season. During the rainy season, the water surface will be maintained at 87 feet above sea level, making the minimum channel depth of the canal 47 feet. As navigation can be carried on at about 41 feet of water, there will be stored for the dry season nearly 6 feet of water. Making due allowances for evaporation, seepage, leakage at the gates, and power consumption, this would be ample for 40 passages

daily through the locks using them at full length, or about 58 lockages a day when partial length is used as would usually be the case. This would permit a larger number of passages of ships than will probably ever be required.

The one all-convincing reason why a sea-level canal was not attempted was the difficulty of controlling the resistless and relentless floods of the Chagres River. This moody and inconsiderate stream has a record of raising 25 feet in 24 hours, and it can be easily imagined what would be the effect on a sea-level canal of a torrent like this pouring into it. By constructing a high-level canal and impounding a great lake, the Chagres can do its worst and practically have no bad effects except to deposit some silt, which can be easily removed by the large dredges always ready for operation in the lake. If the Chagres poured its greatest flood continually for 5 hours and 20 minutes into the lake it could raise it only one foot in that time, and this, in turn, could be immediately counterbalanced if necessary by lowering the gates at the spillway of the Gatun Dam.

From the Gatun Locks through the lake to Tabernilla, a distance of about 16 miles, the channel of the canal will have a width of 1,000 feet, and vessels can proceed at almost full speed. From Tabernilla to Mamei the channel will be 800 feet wide;

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INSPECTING GIANT GATES AT GATUN LOCKS Major Von Herwarth (in white, second from right end), German Military Attaché, and John Barrett (second from left), Director General of the Pan American Union.

Copyright by Brown & Dawson, Stamford, Conn.

from Mamei half way to Gorgona, 700 feet; from there to a point near where the Chagres River strikes the canal, 500 feet; and then for nearly 9 miles through Culebra Cut to Pedro Miguel, 300 feet; from Pedro Miguel Lock to Miraflores Locks and thence to deep water and Panama Bay, 500 feet wide. These widths prove beyond question that the canal will be amply wide for the largest vessels which will ever use it to pass. The maximum width will be 1,000 feet, the minimum 300 feet, and the minimum depth, 41 feet.

After passing through the lake the most spectacular section of the canal is reached-the Culebra Cut. Although this nominally extends. over 9 miles from Gamboa to Pedro Miguel Lock, the really fascinating and overwhelmingly interesting portion is the two or three miles through the summit of the continental divide, lying between Gold Hill on the east and Culebra Hill on

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LAKE AND UPPER ENTRANCE TO GATUN LOCKS

With dam reaching from locks to osite hill, concrete spillway in the center

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