Panama Canal. In June, 1904, Chief Engineer Wallace, Col. W. C. Gorgas, and others sailed to the Isthmus to pursue the great work which had been transferred to the United States, May 4, by the French. Digging in the Culebra Cut was continued, but the chief labor for two years and a half was to remedy the unsanitary conditions, to provide accommodations for the employees, to perfect the organization, to reconstruct and double-track the railroad, and to improve the terminal facilities: necessary preparations for the colossal task. The sanitation of Colon and Panama included repaving, sewerage systems, and fresh water supply, as a part of the war against yellow and malarial fever. A proportionate sum spent on sanitation in the United States would be $12,000,000,000 a year, one-third of the entire amount devoted to all government expenses. Since January, 1907, the work has progressed rapidly, so that the canal is expected to be completed and in operation some time before the date of its formal inauguration January 1, 1915.
In spite of being hampered in many ways, much valuable work was accomplished by Chief Engineer John F. Wallace, who resigned after one year, and by his successor, John F. Stevens. He serving until 1907 is said by Col. Goethals to have laid out the transportation scheme in a manner which could not have been equaled by any army engineer. The engineering skill and the great administrative ability of Col. George W. Goethals, Chairman of the Isthmian Canal Commission, Chief Engineer, President of the Railroad, Governor of the Zone, etc., are so well known and already so highly honored as to need no encomiums here. A benevolent despot, able, wise, just, and honest, it is indeed a pleasure in this day and generation to find one as to whose virtues all are agreed, whose undying fame is as yet free from the malice of petty jealousy.
The length of the Canal, from deep water on one side to the same on the other, that is, from the Toro Point breakwater on the Atlantic side to Naos Island on the Pacific side, is about 50 miles,—40 miles from shore to shore. From the Atlantic entrance, by a channel 41 feet deep with a bottom width of 500 feet, it is seven miles to Gatun, two-thirds of which is in Limon Bay, the rest apparently along a fairly broad river. At Gatun, as everybody knows, are the locks, a double series of three, by means of which the ships will be raised 85 feet to the level of Gatun Lake. This, with an area of 164 square miles, is without doubt the largest artificial sheet of water in the world. The lake naturally has a widely varying depth and a highly irregular shape, with large and small arms, promontories, and islands; but vessels may sail at full speed along a channel from 500 to 1000 feet in width for a distance of 24 miles until at Bas Obispo the Culebra Cut is entered. This, about nine miles long, has a bottom width, except on the curves, of 300 feet only, making a slower rate of speed necessary. At Pedro Miguel the ship will be lowered by one lock to a smaller lake covering 1200 acres, 30 feet below. A mile and a half beyond, at Miraflores, the ship, by means of two locks, will return to sea level, thence sailing on, 8½ miles more, out into the Pacific.
The sail from ocean to ocean will to all be of intense interest, though more highly appreciated by those who visited the region before it was submerged, watched the great shovels cutting away the range of hills which forms the continental divide, and saw the locks in process of formation.
The great Gatun dam seems a wonderful creation, though the only remarkable feature is its size. It should be borne in mind that the extensive surface of the lake among the hills does not cause any greater pressure upon the wall of the dam than if it covered but a single acre; the depth of the water being the determining factor, not the extent of surface. The dam is nearly a mile and a half long at the top; half a mile wide at the bottom, 400 feet at the water surface, and 100 at its crest, designed to be 105 feet above sea level and 20 feet above the normal level of the lake: a very wide margin of safety. Of the entire length of the dam only 500 feet, a small fraction, one-fifteenth, of the whole, will be exposed to the maximum water head, 87 feet. The thickness of the dam is greater than was deemed necessary by engineers, with the result that there is no seepage: but it was thought best to satisfy over-apprehensive Congressmen by the employment of excessive caution. The interior of the dam is an impermeable mixture of sand and clay obtained by dredging above and below, placed between two parallel ridges of rock and ordinary material obtained from the steam-shovel excavations. The upstream slope of slight grade is thoroughly riprapped ten feet below and ten above the mean water level. The 21 million cubic yards of material composing the dam, which covers 400 acres, is sufficient to build a wall three feet high and thick nearly halfway around the world.
The Gatun Lake will receive all the waters of the Chagres basin of 1320 square miles and will contain at its ordinary level 206 billion cubic feet of water. An outlet, an obvious necessity, is provided in the spillway, a cut through a hill of rock nearly in the center of the dam, southwest of the locks. This opening, lined with concrete, is 1200 feet long and 285 feet wide, with the bottom, at the upper end ten feet above sea level, sloping down.
Until the construction of the dam was well advanced the water from the Chagres and its tributaries flowed out through this opening. Then it was closed at the upper or lake end by a dam of concrete 808 feet long in the form of an arc of a circle, its crest 69 feet above the sea. Upon this, 13 concrete piers rise to a height of 115.5 feet, with steel gates by which the water level of the lake will be regulated.
The immense double locks deserve more than a cursory glance. Similar in construction and dimensions, each has a usable length of 1000 feet and a width of 110 feet. The chambers have floors and walls of concrete with mitering gates at each end. The walls, perpendicular on the inside, are 45 to 50 feet thick near the bottom, but the outer walls narrow from a point 24 feet above the floor to a thickness of 8 feet at the top. The middle wall separating the double locks is 60 feet thick and 81 high, with both faces vertical; but in the upper part it is not solid. A tunnel in the wall has three divisions, the lowest for drainage, the middle for electric wires to operate the gate and valve machinery, the highest as a passage way for the operators. An enormous amount of concrete has been employed for the locks, four million or more cubic yards, with as many barrels of cement, enough to make a sidewalk 9 feet wide and 6 inches thick more than twice around the world.
Matching the walls are immense steel gates, 7 feet thick, 65 feet wide, and from 47 to 82 feet high, with a weight of from 390 to 730 tons each. At the entrance to the locks are double gates, also at the lower end of the upper lock in each flight, in case of ramming by a ship accidentally breaking through the fender chain; for there are 24 chains in addition to the gates, to prevent the gates being rammed by a ship under its own steam or having escaped from the towing locomotive. The chains will be lowered into a groove to allow the ships to pass.
Ships will not be permitted to enter the locks under their own steam, but will be towed through by electric locomotives, usually four to each vessel, two ahead and two astern, the latter to keep the vessel in the middle, and in the right place. The gates and valves are also operated by electricity, with power obtained through water turbines from the head created by Gatun Lake. The locks will be filled and emptied by a system of culverts, one of which, about the size of the Hudson River tunnels of the Pennsylvania Railroad, 18 feet in diameter, extends along the side and middle walls, with smaller branches under the floor of the locks. The water enters and leaves by holes in the floor. The culverts are so arranged as to economize water by passing it from one twin lock to the other. To save both time and water each lock chamber has a single gate near the middle dividing it into two parts, only one of which will be used for vessels less than 600 feet long. To fill and empty a lock will require about 15 minutes: to pass through the three at Gatun, about an hour and a half, and as much more to go down the locks on the Pacific side. The entire passage through the Canal will occupy 10 or 12 hours according to the speed of the ship, in the narrower parts all being obliged to go slowly. While it is hoped that the first steamer will pass through the Canal in December, 1913, if not earlier, there is no expectation of its being open for general traffic before the summer of 1914.