Engineering Wonders of the World
Volume III

168 ENGINEERING WONDERS OF THE WORLD. A LÜBECKER EXCAVATOR SCOOPING EARTH FROM THE PRISM OF THE NEW ERIE CANAL. of many locks. Now, the longest possible level route will be chosen, and the descent —now made through many tedious locks— will be made, where possible, in a single abrupt drop, reducing greatly the number of locks, the time now required for lockage, and the personnel-and equipment. The application of the new principle will be exploited in the resuscitation of the Erie State Canal of New York, beginning at the town of Lockport, where there are now five old-style locks. These five locks will be re- placed by a pair of the new- style pneumatic lifts, having an extreme lift of 62| feet (trebling the high- est lift now obtainable). The new device will cost $500,000 in itself, and will have a capa- city six times greater than the old locks, which cost almost $700,000. A pneumatic lock consists of two units. Each unit has an upper boat chamber, to the bottom of which is attached an inverted caisson. When submerged, this caisson forms New Erie or New York State Barge Canal. a natural seal for the compressed air inside. The locks work in pairs, one rising when the other falls. They move up and down in steel guiding-frames, and may be built either side by side or end on to one another. An immense tube, fitted with a valve, per- mits the air to pass quickly from one of the compressed-air compartments to the other. The flow of compressed air is constant, except when a vessel has been locked through and the valve is closed. An extra pressure of air against the elevated lock from beneath, assisted by anchors above, holds the elevated lock in place. Meanwhile, the depressed caisson settles quietly into the lower level of the canal. A vessel is admitted to either or both locks, and as a vessel displaces only its own weight of water, the compressed air keeps the locks in balance when the gates are closed. Upon an additional quantity of water being let into the chamber of the elevated lock, that lock sinks, forcing the air in the caisson