Page:The National Geographic Magazine Vol 16 1905.djvu/521

has, in some capacity, been associated with it from 5 to 25 years and knows the tremendous difficulties to be overcome. Their decision will be submitted to the Isthmian Canal Commission which may accept it or not as they deem best. The Isthmian Canal Commission recommend to Congress, which alone has the power to determine the plan.

Next to the sea-level canal, the most interesting project is that proposed by Mr Bunau-Varilla. Mr Varilla asserts that it will take the United States many years to construct a sea-level canal, owing to the great difficulty we shall have in securing sufficient laborers. He advocates a plan of his own invention, which he says can be completed in four and one-half years. The canal would, be large enough to handle double the amount of traffic which statisticians have calculated will use the canal during the next generation, and can gradually be converted into a sea-level canal without interruption of traffic. Mr Bunau-Varilla's preliminary canal is not unlike that recommended by the first Isthmian Commission, and shown on our supplement. The most interesting feature of the scheme is a dam at Bohio, built entirely of mud and without any artificial core, and of nearly twenty-five times the width of the dam proposed by the Isthmian Commission. The dam would be formed of sandy clay, which is to be sucked up by dredges from the Chagres Valley, and then forced through pipes and deposited in the required position and allowed gradually to harden. The mud, Mr Varilla says, would harden in the manner of cement, and in this way the dam could be constructed at very small expense.

The amount of water that would filter through the ground below the dam would be insignificant. The dam would form a lake, similar in position to the lake shown on the map and extending to the vicinity of Gamboa. At Gamboa another dam built of concrete and steel and strengthened by embankments of earth would form a second lake outside the canal line. Mr Bunau-Varilla proposes two locks at Bohio, ascending to Lake Bohio, and two more locks near Obispo for the ascent to the summit level, which extends from Obispo through Culebra Cut. As the summit level is 130 feet above the sea, the amount of excavation in the Culebra Hill is comparatively small. There are four locks on the Pacific end, making eight in all for the canal.

This serviceable lock canal, which is to be put into commission four and one-half years from the day of commencement, Mr Bunau-Varilla proposes to lower to sea level entirely by dredging. Lake Gamboa is to furnish the electric power to drive the dredges, while into it is to be dumped all the excavated rock and mud. The flow of excavated rock and ground into Lake Gamboa will go on, says the designer, at the rate of 4,000 cubic yards an hour, or 90,000 cubic yards a day, with a very ample margin of safety for accidents. Lake Gamboa, owing to its enormous dimensions, may absorb many times the total cube to be excavated from the canal.

The following paragraphs are quoted from Mr Bunau-Varilla:

"In all countries of the world dredging is incomparably superior to dry excavation when the ground necessitates no mining. On the Isthmus of Panama this advantage is transformed into an enormous superiority. If there is an instrument of work which counterbalances as much as it is physically possible all the evil influences of the Isthmus, it is the dredge. It counter-balances them because, first, it is the only excavating instrument where the