ON PHYSICAL AND ENGINEERING FEATURES OF THE MERSEY. 563 
feet in length by 300 feet in width, and has an aggregate quayage of 
2,469 feet, amply provided with single and double storey sheds of large 
size with improved crane appliances. The White Star Company occupy 
berths on the north and south sides of this dock, and there their largest 
steamers lie. 
In connection with the Canada a new passage 90 feet in width, with a 
bridge over, has been constructed, to join up with the Huskisson system. 
The new Half-tide Dock occupies the site of Sandon Basin and 
Wellington Half-tide Dock, and will afford room for a large number of 
great vessels. The sills of the river entrances are laid at a much lower 
level than any of the existing docks, viz., 20} feet below Old Dock Sill, 
so that vessels of the deepest draught will be able to enter and leave the 
Half-tide on any tide in the year. On neap tides this dock will be used 
as a lock for vessels passing between the River and docks, which latter 
will on such tides be maintained on the impounded system, powerful 
pumps being provided in positions near to the Half-tide dock. 
The new Graving Dock, 920 feet long, will be constructed out of the 
east quay of Canada Dock immediately north of the Branch Dock. 
Having now described the dock extensions most recently constructed 
and in hand at Liverpool, the Author will, before mentioning the accom- 
-modation provided for some of the most noteworthy trades, refer shortly 
to the history of that portion of the Mersey Dock Estate situate on the 
Cheshire shore at Birkenhead. 
In 1855 the dock authorities of that day applied for Parliamentary 
powers to extend their docks on the Lancashire side of the river. This 
was only partially acceded to, and, in lieu of powers for their complete 
proposal, it was arranged that the Birkenhead Docks, then belonging to 
two independent authorities and only partially developed, should be 
purchased by the Liverpool Corporation, who in those days administered 
the affairs of the Liverpool Estate. Two years later the administration 
of the combined Liverpool and Birkenhead Estates was handed over to an 
independent Trust to be called ‘ The Mersey Docks and Harbour Board.’ 
The Birkenhead system, therefore, now forms an integral portion of the 
Mersey Dock Estate, and is worked in complete unison with the Liverpool 
system. 
; The Birkenhead Docks are constructed on the site of a tidal creek, 
known as Wallasey Pool, which extended inland for about two miles from 
the left bank of the River, and formerly was the outlet of the drainage of 
the low lands of the Leasowes, lying between the Dee and the Mersey. 
The original design, by the late eminent engineer, Mr, James Meadows 
Rendel, F.R.S., having been partially carried out, was mainly completed 
on the same lines by Mr. John Hartley, who, however, introduced several 
important alterations when it came into Dock Board hands. 
The main features of the scheme were two large docks, called the East 
and West Floats, of 120 acres in area, occupying a large portion of the 
pool, the connection between these docks and the River being by means of 
a lock, and a half-tide dock called the Alfred, the sills of which, at the 
pret end, are nine feet below datum, and at the River end twelve feet 
low. 
On taking charge of the engineering of the Estate in 1861, the Author 
carried out these works to completion, but made seyeral important altera- 
tions in Mr. Hartley’s design, unnecessary now to particularise. In con- 
sequence of the entire area of the Float, East and West, being excavated 
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