Hydraulic Elevator for Canals.—For avoiding the use of locks on canals, Mr. E. Clark, au English engineer, has introduced an ingenious plan, which is found to be specially serviceable in situations where the difference in height to be overcome is so considerable that ordinarily a series of locks would be required. His plan involves the use of a system of elevators by which the boats are raised and lowered vertically by the application of the principle of hydrostatic pressure. The first elevator of this type was built by Clark at Anderton, England, on the Trent and Mer sey Canal, and operated so well that it has been adopted elsewhere.
Neufosse Canal Elevator.—A conspicuous example of this system (pi. 51, fig. I) is seen on the Neufosse Canal, which connects the ports of Calais, Gravelines, and Dunkerque with the system of canals of the North. The traffic on tbis canal is enormous (reaching eight hundred thousand tons per annum), and at a point called Les Fontinettes, about two and one half miles from St. Omer, it was necessary to have a series of five locks, at which boats were often detained for nearly a week waiting their turn to pass. To avoid this serious inconvenience, the administration decided to adopt the plan which Clark introduced at Anderton. This was success fully accomplished. The apparatus consists essentially of two lock-cham bers of plate iron. Each of these rests at its centre on the head of a piston which works in the cylinder of a hydraulic press placed in the centre of a well. Communication between the two presses is established or shut off by a sliding valve. 1,Vhen the valve is open, there is a hydrostatic balance. If one of the lock-chambers is more heavily loaded than the other, it de scends and forces the lighter one to ascend.
In practice, the upper lock-chamber, with its boat, is always more heavily weighted by the admission of water into it than the chamber and its boat at the lower level, so that, being overweighted, the upper chamber must descend with its burden, while the lower one must of necessity as cend with its load. In operation, a boat is admitted to each of the cham bers, one being at the lower and the other at the upper level, and the gates of the canal and of the chambers are closed to isolate the chambers. Now the sliding valve establishing communication between the presses is opened, and the heavier chamber above, which is always surcharged with water ballast, commences to descend, forcing the lower one to rise, until their relative positions have been reversed, when, the transfer having been effected, the closing of the sliding valve holds the chambers in position, and, the gates being opened, the boats may proceed on their respective journeys. The difference of level overcome by the hydraulic lift at Les Fontinettes is 43 feet. The lock-chambers are 13o feet long, r9 feet wide,
and 7 feet deep, and they can accommodate boats of three hundred tons burden, the largest that ply the canals of the North. The weight of one of these chambers when filled with water is eight hundred tons, so that a mass of sixteen hundred tons is set in motion at every mananivre.
Another and more recent example of this system is that erected at La Lotivire on the Canal du Centre in I3elgium. This lift is even largver than that just described. Its height is 5o feet; length of the chambers between the gates, 141 feet 7 inches; width, 1SX feet; the depth of water, 8Y: feet; the diameter of the rams, 6 feet 634 inches; the weight to be lifted, eleven hundred tons; and the displacement of' the largest boat to be accommo dated, four hundred tons. The hydraulic cylinders are each formed of nine lengths of cast iron hooped continuously Ixith steel. The rams are 63 feet 11 inches long, and are formed of eight sections of cast iron 7 feet long and 2.95 inches thick. The lift is operated in the same manner as that above described.
Earis's Projeded Shifi-railzvay.—It will doubtless be of interest to many readers to have introduced at this point a brief account of the exceedingly bold and original project of the late Captain James B. Eads (the constructor of the great steel bridge over the Mississippi River at St. Louis, p. 268) for transporting- vessels from ocean to ocean across the American isthmus at Tehuantepec (fii. 51, figs. 4-7). The project has been thwarted to some extent by reason of the death of its chief promoter, but it is by no means improbable that it may one day be realized.
The plans of the Tehuantepec ship-railway are briefly as follows: At each terminus a basin be excavated leading to a dock. In this dock will be placed a pontoon which, like an ordinary lifting dock, will be capable of raising the vessels. By providing it with longitudinal and transverse bulkheads, it will be given tl:e requisite strength to bear the enormous loads it will be called upon to support. It is proposed to make this pontoon about 45o feet long, 75 feet wide, and from 12 to 15 feet deep. It will be sunk bv opening sluice-g-ates in its sides, and raised by powerful pumps, which will withdraw the water from its interior and discharge it into the surrounding dock or basin. The vertical movements of the pontoon will be guided bv large anchor-rods or weighted cylinders securely anchored in the foundations of the dock. They will be constructed in such a manner as to pass freely through the pontoon, but will be separated from its water spaces, and the heads of these rods will prevent the pontoon from rising above a certain level, and will resist the buoyancy when the vessel has beet: run off on to the railway.