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.
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