Page:Popular Science Monthly Volume 61.djvu/268

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wind enough to take them out of Panama Bay are so serious as to constitute a material objection to the location for a ship canal on the Panama route. This difficulty undoubtedly exists at times, but the simple fact is to be remembered that Panama was a port for sailing ships for more than two hundred years before a steamship was known. The harbor of Panama, as it now exists, is a large area of water at the extreme northern limit of the bay, immediately adjacent to the City of Panama, protected from the south by the three islands of Perico, Naos and Culebra. It has been called a roadstead. There is good anchorage for heavy draft ships, but for the most part the water is shallow. With the commission's requirement of a minimum depth of water of 35 feet, a channel about four miles long from the mouth of the Rio Grande to the six-fathom line in Panama Bay must be excavated. This channel would have a bottom width of 200 feet with side slopes of one on three where the material is soft. Considerable rock would have to be excavated in this channel. At 4.41 miles from the six fathom line is located a wharf at the point called La Boca. A branch of the Panama Railroad Company runs to this wharf, and at the present time deep draft ships lie up alongside of it and take on and discharge cargo, as do the trains of the Panama Railroad Company. This wharf is a steel framed structure, founded upon steel cylinders, carried down to bedrock by the pneumatic process. Its cost was about $1,284,000. The total cost of this excavated channel, leading from Panama Harbor to the pier at La Boca, is estimated by the commission at $1,464,513. As the harbor at Panama is considered an open roadstead, it requires no estimate for annual cost of maintenance.

Starting from the harbor of Colon the prism of the canal is excavated through the low and for most part marshy ground to the little village called Bohio. The prism would cut the Chagres River at a number of points, and would require a diversion channel from that river for a distance of about five miles on the westerly side of the canal. Levees or protective embankments would also be required on the same side of the canal between Bohio and Gatun, the Chagres River leaving the canal line at the latter point on its way to the sea.

The principal engineering feature of the entire route is found at Bohio; it is the great dam across the Chagres River at that point, forming Lake Bohio, the summit level of the canal. The new Panama Canal Company located this dam at a point about seventeen miles from Colon, and designed to make it an earth structure suitably paved on its faces, but without any other masonry feature. Some borings had been made along the site and test pits were also dug by the French engineers. It was the conviction of the Isthmian Canal Commission, however, that the character of the proposed dam might be affected by