The Mersey Tunnel was lately opened by the Prince of Wales, and, as the London Standard says, after an infancy of troubles and failures, and a ten years' middle age of inaction, the Mersey Tunnel emerges into notoriety under the hands of Mr. James Brunlees and Mr. C.D. Fox, and of Mr. Waddell, the contractor, as a triumph of engineering skill. The tunnel is 1,250 yards in length. It is driven through solid, but porous, red sandstone, through which the water has percolated in volumes during construction, at a level of about 30 feet below the bed of the river. It is lined throughout with blue bricks, the brickwork of the invert being 3 feet in thickness. Its transverse section is a depressed oval 26 feet in width and 21 feet in height, and it contains two lines of railway. At a depth of about 18 feet below the main tunnel there is a continuous drainage culvert 7 feet in diameter, entered at intervals by staple shafts. There are two capacious underground terminal stations 400 feet long, 50 feet broad, and 38 feet high, and gigantic lifts for raising 240 passengers in forty seconds, from more than three times the depth of the Metropolitan Railway to the busy streets above.
These splendid lifts, the finest in the world, are now, through the engineering skill of Messrs. Easton & Anderson, like the tunnel, accomplished facts; and their construction and working were tested and reported on in high terms of favor by the Government Inspector, General Hutchinson, a few weeks ago. At the Liverpool end the direct descent to the underground platform of the Mersey Railway is about 90 feet; at the Birkenhead end the depth is something more.
The description of the Liverpool lifts will well suffice also for the Birkenhead lifts. The former are under James Street, where above ground, rising in lofty stateliness, is a fine tower for the hydraulic power, the water being intended to be stored in a circular tank near its summit, the dimensions of which will be 15 feet in diameter and its internal depth 9 feet. From the level of the rails of the Mersey Railway to the bottom of this water-tank the vertical distance is 198 feet. At the western side of the subterranean railway there is, above the arrival platform, a "lower booking-hall," or, more properly, a large waiting room, 32 feet square and 29 feet high, the access to which on this side is by a broad flight of steps rising 12 feet, and to and from which all passengers on the departure platform have communication by a lattice bridge 16 feet above the line of rails. From the western side of this hall the passengers will have access to the three lifts, and will thence ascend in large ascending rooms or cages, capable of containing one hundred persons each, to the upper booking-hall on the ground level of James Street. Intermediate in height between the lower and upper halls the engine-room for the pumps is located.
From the lower hall also there is provided, independent of the lifts, an inclined subway, leading up toward the Exchange. In this lower subterranean chamber there are four doorways, 5 feet wide, three of them being fitted with ticket gateways, and leading to the three lift-shafts, excavated in the rock, and lined, where needed, with brick. In each of these shafts, which are 21 feet by 19 feet in sectional area, a handsome ascending wood-paneled room, or cage, formed of teak and American oak, is fitted, its dimensions in plan being 20 feet by 17 feet, and its general internal height 8 feet; but in the central portion the roof rises into a flat lantern 10 feet high, the sides of which are lined with mirrors that reflect into the ascending-room the rays of a powerful gas-lamp. The foundation of this room is a very stiff structure, consisting of two wrought-iron special-form girders crossing beneath it, the cross, 14 inches deep, connecting them being of steel, and forged from a single ingot. The central boss of the cross is 22 inches in diameter, and in this is bored out a central cavity, into which the head of the steel ram, 18 inches in diameter, is fitted; the ram itself being built up of steel cylinders or tubes, 11 feet 3 inches in length, which are connected together by internal screws.
There is also a central rod within the ram, as an additional security. The ram descends into a very strong cast-iron cylinder, 21 inches internal diameter, which is suspended in a boring 40 inches internal diameter, and carried down to a depth of over 100 feet in the rock. The two iron girders under the frame of the ascending-room or cage cross the entire lift space, and then at their outer ends are attached to four chains which rise over pulleys fixed about 12 feet above the floor of the upper booking-office. These chains thence descend to suspend two heavy counterweights, so arranged as to work in guides and to pass the ascending-room in the 12 inch interspace between the cage and the side walls of the shaft. These chains are of 1-1/8 inch bar iron, and have each been tested with a load of over 15 tons. The maximum load which can ever come as a strain upon any chain is about three tons. Two chains are attached to each counter-weight, and special attention has been paid to the attachments of these chains to the cage girders. The stroke of each hydraulic lift is 96 feet 7 inches.
In the engine-room there are three marine boilers, each 6 feet 6 inches diameter and 11 feet 6 inches long, and three pairs of pumping engines of patented type, each capable of raising thirty thousand gallons of water per hour from the waste tanks below the engine-room to the top tank of the tower above ground. There are three suction and three delivery mains, and these are connected direct to the lifts by a series of change sluices, admirably, neatly, and handily arranged in the engine-room by Mr. Rich, and in such a way that any engine, any lift, or any supply main can be disconnected without interference with the rest of the system. When the tower tank is completed, it alone, under any circumstances, would be able to supply the lifts if every pumping engine were stopped. But if any or all the engines were working, they would automatically assist the top tank, for nominally they will keep the top tank exactly full, and will then stop of themselves. The tower, as we have indicated, is not yet completed, and the pumping engines are consequently doing all the work of the lifts.
The ascent and descent of the cages is effected by the attendant who accompanies the passengers, by means of a rope arrangement.
Each cage or room is intended ordinarily to take a maximum freight of 100 passengers, calculated at about 15,000 lb. The hydraulic ram weighs about 11,000 lb., the iron frame and cross of the cage about 6,500 lb., and the cage itself about 13,200 lb., the total being about 30,700 lb. The mass in motion when a cage is fully loaded is estimated at 63,000 lb. dead weight. The journey of elevation will ordinarily be made within one minute, but in the experimental trials which have been made the full journey has actually been accomplished in 32 seconds. In the Board of Trade tests under General Hutchinson, weights to the extent of 15,000 lb. were variously shifted, and in certain cases concentrated in trying localities, but the cage stood the trials without any appreciable change of form, and in neither the cage nor the chains were any objectionable features developed. The three lifts can be worked singly or combined, so that the accommodation is always ready for from 100 to 300 persons. Further railway connections between the Mersey Subaqueous Railway and the surrounding land lines than those which yet exist are in contemplation.
All the booking-halls, waiting-rooms, etc., etc., in connection with the four stations have been laid with Lowe's patent wood-block flooring. The blocks are only 1-1/2 inches thick, but, being made of hard wood and securely fastened to the concrete bed with Lowe's patent preservative composition, they cannot become loose, and will wear for a long series of years, until, in fact, the wood is made too thin by incessant traffic.
The engineer, Mr. Fox, and the architect, Mr. Grayson, are much pleased with the work, especially as it is so noiseless and warm to the feet. These floors ought to be adopted more frequently by railway companies in connection with their station buildings, as "dry rot" and "dampness" are effectually prevented, and a durable and noiseless floor secured.