In substance the Canal works consist, first, of an enormous dam (at Gatun), which holds up the water of the river Chagres so as to flood a valley twenty-four miles long; secondly, of a channel—nine miles in length—(the Culebra Cut)—which carries the valley on through a range of low hills; and, thirdly, of a set of locks at each end of this stretch of water that are connected by comparatively short approaches with the sea. The surface of the lake will be from 79 to 85 feet above sea-level, and vessels will be raised to this height and lowered again by passing through a flight of three locks upward and another flight of three locks downward. The passage of both flights of locks is not expected to occupy more than three hours, and ships should complete the transit of the Isthmus—a distance of about fifty miles—within twelve hours at most. The design of the work offers nothing that is new in principle to engineering science. Dams, cuttings, and locks are familiar contrivances. But they are on an immensely larger scale than anything which has previously been attempted. The area of the lake of impounded water will be 164 square miles, and it has been doubted whether the damming of so large a mass of water, to a height of 85 feet, could safely be undertaken. But this portion of Central America is apparently not liable to earthquakes. And the dam is so large as to be a feature of the earth's surface. It is nearly half a mile broad across its base, so that although its crest is 105 feet above sea-level its slope is not very perceptible. Its core is formed of a mixture of sand and clay, poured in from above by hydraulic processes. This has set hard, and is believed to be quite impervious to water at a much higher pressure than that to which it will be subjected. In the center of the river valley—a mile and a half broad—across which the dam has been flung, there very fortunately arose a low rocky hill. This is included in the dam, and across its summit has been constructed the escape or spill-way. During seasons of heavy rain the surplus discharge of river water will be very heavy, and a cataract will pour over the spill-way. But it will rush across a bed of rock, and will be unable to erode its channel. And it will be employed to generate electrical power which will open and shut the lock-gates and generally operate the Canal machinery. The river Chagres will energize the Canal as well as fill it.
The locks are gigantic constructions of concrete. Standing within them one is impressed as by the mass of the Pyramids. The gates are hollow structures of steel, 7 feet thick. Their lower portions are water-tight, so that their buoyancy in the water will relieve the stress upon the bearings which hinge them to the lock-wall. Along the top of each lock-wall there runs an electric railway; four small electric locomotives will be coupled to a vessel as it enters the lock approach, and will tow it to its place. The vessel will not use its own steam. This will lessen the risk of its getting out of hand and ramming the lock-gate, an accident which has occurred on the big locks that connect Lake Superior with Lake Huron. So catastrophic would be such a mishap, releasing as it might this immense accumulation of water, that it seemed desirable at whatever expense to provide additional safeguards against it. There are in the first place cross-chains, tightening under pressure, which may be drawn across the bows of a ship that threatens to become unmanageable. Secondly, the lock-gates are doubled at the entrance to all the locks, and at the lower end of the upper lock in each flight. And, thirdly, each flight of locks can be cut off from the lake by an "emergency dam" of peculiar construction. It is essentially a skeleton gate, which ordinarily lies uplifted along the top of the lock-wall, but can be swung across, lowered, and gradually closed against the water by letting down panels. In its ordinary position it lies high above the masonry—conspicuous from some distance out at sea as a large cantilever bridge, swung in air.
Peculiar difficulties have been encountered in establishing the foundations of the locks. The lowest of each flight are planted in deep morasses, and could only be settled by removing vast masses of estuary slime to a depth of 80 feet below sea-level. The sea was cut off and a dredger introduced, which gradually cleared its way down to the bottom rock. But the troubles which the American engineers will remember are those which have presented themselves in the Culebra cutting. The channel is nine miles long. Its average depth is between 100 and 200 feet, but at one point it reaches 490 feet. The formation of the ground varies extraordinarily. At some points it is rock; at others rock gives place to contorted layers of brilliantly colored earth which is almost as restless as quicksand. Unfortunately, it is at places where the cutting is deepest that its banks are most unstable. The sides of the lowest 40 feet of the excavation—the actual water channel—are cut vertically and not to a slope; in a firm formation this reduces the amount of excavation, but in loose material it must apparently have increased the risk of slides. But, however this may be, slips on a gigantic scale were inevitable. The cutting is an endeavor to form precipitous slopes of crumbling material under a tropical rain-falclass="underline" it may be likened to molding in brown sugar under the rose of a watering-pot. The banks have been in a state of constant movement, and are broken up into irregular shelves and chasms, so that at some points the channel resembles a natural ravine rather than an artificial cutting. One thing is certain,—that for some years to come the channel will only be kept open by constant assiduous dredging. But it is, of course, easier to dredge out of water than to excavate in the dry. The material excavated from the Culebra channel will aggregate nearly one hundred million cubic yards. Some of it has been utilized in reclaiming land; much has been carried out to sea and heaped into a break-water three miles long, which runs out from the Panama or southern end of the Canal, and will check a coast-ways current that might, if uncontrolled, silt up the approach. The Canal is a triumph, not of man's hands, but of machinery. Regiments of steam shovels attack the banks, exhibiting a grotesque appearance of animal intelligence in their behavior. An iron grabber is lowered by a crane, it pauses as if to examine the ground before it, in search of a good bite, opens a pair of enormous jaws, takes a grab, and, swinging round, empties its mouthful onto a railway truck. The material is loosened for the shovels by blasts of dynamite and, all the day through, the air is shaken by explosions. Alongside each row of shovels stands a train in waiting; over a hundred and fifty trains run seaward each day loaded with spoil. The bed of the Canal is ribboned with railway tracks, which are shifted as required by special track-lifting machines. The masonry work of the locks is laid without hands. High latticed towers—grinding mills and cranes combined—overhang the wall that is being built up. They take up stone and cement by the truck-load, mix them and grind them—in fact, digest them—and, swinging the concrete out in cages, gently and accurately deposit it between the molding boards. How sharp is the contrast between this elaborate steam machinery and the hand-labor of the fellahín who patiently dug out the Suez Canal! But there are, so to speak, edges to be trimmed: this mass of machinery is to be guided and controlled, and there is work to employ a staff of over thirty thousand men. Some four thousand of them are Americans, who form a superior service, styled "gold employees" in order to avoid racial implications. Their salaries are calculated in American dollars. The remainder, classed as "silver employees," are paid in Panama dollars, the value of which is half that of the American. Two series of coins are current, one being double the value of the other; and, since the corresponding coins of the two series are of about the same size, newcomers are harassed by constant suspicions of their small change. The "silver employees" number about twenty-six thousand. Some of them are immigrants from Europe—mostly from Italy and the north of Spain—but the great majority are negroes, British subjects from Jamaica and Trinidad. It was foreseen that if negroes from the Southern States were employed, the high wages rates might unsettle the American cotton labor market: so it was decided to recruit from British colonies, and it is not too much to say that, so far as the Canal is hand-made, it is mainly the work of British labor. Several hundreds of Hindus have found their way here; they are chiefly employed upon the fortifications, because, it is said, they are unlikely to talk about them. These British colored laborers, with their families, constitute the bulk of the population of the Canal Zone: the town of Panama swarms with them, and one sees few of any other class in the streets of Colon. The American engineers have thus been working with a staff that can claim the protection of the British Minister; and it is pleasing to an Englishman to hear on every side the heartiest tributes to the energy, tact, and good sense of England's representative, Sir Claude Mallet. At the outset the negro laborers were exceedingly suspicious of the American authorities, and were ready to strike on the smallest provocation: they have refused to take their rations until Sir Claude has tasted them. He possesses the complete confidence of the British labor force, and indeed the Hindu immigrants, who deposit money at the Consulate, will hardly wait to obtain receipts for it.