The Great Events by Famous Historians

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.