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Fig. 8. — Gatun lower lock, showing steel forms, overhead cableways, temporary concrete dam at lower end of lock, and partly completed sea-level canal in the distance. Note tower on left from which overhead cables run to similar tower on right (not shown). Materials for the locks were handled by these cables.
saved in building, the actual cost of maintenance would be less. After being built, it would be easier to enlarge the lock canal than the sea-level canal. Moreover, what has been actually demonstrated in making and operating the great lock canal, the Soo, a more important artery of traffic than the great sea-level canal, the Suez, goes to support the opinion of the minority of the Consulting Board of Engineers and of the majority of the Isthmian Canal Commission as to the superior safety, feasibility, and desirability of building a lock canal at Panama.
The law now on our statute books seems to contemplate a lock canal. In my judgment a lock canal, as herein recommended, is advisable.
On June 27, 1906, Congress passed a joint resolution which approved the lock canal proposed by the minority, and finally closed the case. This was more than one year after the appointment of the Board of Consulting Engineers. Many details, as well as many problems of importance, were not finally determined by the board and required consideration by the Isthmian Canal Commission. It will not be necessary to describe the detailed processes and the steps by means of which these matters were finally determined, except incidentally when studying some of the important elements of the canal. A general account of the canal as it is actually being built will now be given, to be followed by descriptions of its important parts.
GENERAL DESCRIPTION OF THE CANAL
The sea-level approach channel from the Caribbean Sea lies within Limon Bay for 43 miles. (See plan No. 2.) It is 500 feet wide on the bottom, with side slopes of one vertical to three horizontal, and having a depth of 41 feet below mean sea level. (See plans Nos. 4 and 5.) The range of the tide is about 2 feet. The alignment is straight for 54 miles from the entrance as far as the Mindi Hills, at which point the American canal intersects the comparatively insignificant old French canal. There is a slight bend of long radius at Mindi Hills, and then a straight run of 11 miles to Gatun Locks. We have passed from the valley of the Mindi River into the valley of the Chagres, and are face to face with one of the great problems of the canal construction, namely, the handling of the torrential Chagres River. After weighing several other schemes, that finally adopted consists of the formation of a lake measuring about 24 miles on the canal axis from Gatun to Bas Obispo. The length of the lake in the other direction will be over 30 miles. The lake is formed by the construction of an earth dam of unusual dimensions extending across the valley at Gatun. The dam does not seem artificial to the eye, but appears as one of the major features of the landscape. After the lake is filled, the flow of the Chagres into it will be discharged by the carefully designed concrete spillway, which cuts through the middle of the great earth dam at a point where a rocky eminence afforded a safe location. The normal water surface of Gatun Lake will be 85 feet above mean sea level, but provisions are made so that the water surface can be carried at any elevation between 80 feet and 87 feet.