The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1855-10-30 00:00:00

BIRKENHEAD DOCK.

The following report from Mr. J. Hartley, on the subject
of the new works at the Birkenhead docks, was read :

TO THE CHAIRMAN OP THE WORKS COMMITTEE

Sin,—ln accordance with the resolution of your committee
of the 16th instant, `that the surveyor be instructed to pre-
pare a plan and report embracing the suggestions made at the
last meeting of the committee, when Messrs. Charles Mclver,
Hamilton, and-John Laird attended, to afford information as
to the probable requirements of large class steamers, as
regards dimensions, length, breadth, draught of water,- &c.'
I now beg to lay before you a plan carrying out the sug-
gestions made by those gentlemen, so far as they related to
the construction of the proposed entrances to the great float
or pool.
. The principle of the design does not differ from that of
plan No. 1, already submitted by me. The alteration consists
merely of the increase of the width of the large lock from 80
to 100 feet, and in the recommendation that its sill should be
laid at the depth of 12 feet instead of 10 feet below the level
of the old dock sill. It was also stated to be desirable that
the sill of the small lock should be laid deeper. I think if
this latter sill is laid at the depth of 8 feet below the datum
in place-of 5 feet, as proposed, it will be as deep as can be
necessary for the class of craft for which- it is designed. At
average spring tides - vessels drawing under 6 feet of water
would be able to pass over the sill after the first two hours
flood tide, and at neap tides vessels of that draught might pass
in and out during the whole period of low water. The
practice with regard to craft bound upwards-towards Run-
corn, in tow of steamers, is to despatch them about three
hours before high water, which enables them to- arrive at the
shallow parts of the upper channel as soon as they have water
over them ; should they start earlier they would have- to wait
there. I may mention that the outer sill of the Duke's Dock
is four feet below the old dock sill-, and I am informed by
Mr. Pendlebury, the-manager there, that two feet additional
depth is all that •he should under any circumstances, require
for the purposes of his trade. lam therefore led to believe
that the depth of 8 feet, as now proposed, would be ample.
As regards coasting vessels- being able to get into dock after
two hours flood or spring tides, and at allperiods during.
neaps, would be an advantage which has not been hitherto
afforded them, and would- enable them to be got in and out
prior to the time when the- larger class of shipping would be
passing; and it must be- borne in mind, that at any time
when greater depths or earlier access might be required, or on
occasions of large arrivals,- these vessels might be passed
through the 50-feet lock, as at that time it would be un--
occupied by the larger class of shipping.
" With respget to the suggestions of altering the width of
the large lock to 100 feet, and adding two feet to its proposed
depth, see no physical difficulty in carrying it into effect.
The hindrance to - laying the sills- of wide entrances at the
depth proposed arises not only,- as I before stated, from the
trouble of keeping the platforms- of the gates clear of sand,
which increases with the area of the platform, but there is also
the danger of not being able to maintain a proportionate depth
in the outer- basin. In proposing to lay the flooring of the
outer basin 177 feet below the old dock sill, I have had this
danger in view, and have allowed a considerable margin of
depth below that at which I proposed-to lay the large sill, so
that in case the sluicing power proposed to be adopted should
all
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nimiteainhtawiantetrh,eafnuldlevdeapitiyh,:ihreear should
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as
upon the sills. So far as regards the approach to the 50-feet
entrance, I see no impediment to its maintenance which may
not be overcome, as the channel thereto will be along the
south wall, and within the efficient action of the sluices ; the
obstruction, if it exists, will be in the centre of and near the
entrance of the lain, at the greatest distance from the power
of the sluicing water. This may also be removed, and the
depth maintained by dredging or other means-; but it must be
expected that if we lay the sills at these increased depths, our
memaiblanrerraassumgmenetnstedin,manaciintthaiantinhfntraaireeefficiency will s
will arise
be anticipated and borne with.
" I am, sir, yours very respectfully,.
tbehatinmluikset
pR:J3Bi HARTLEY.

"Dockyard, 19th Cotober, 1855."
Some desultory conversation followed, in the course of
which the Chairman intimated that he wished, to state it was
the opinion of Mr. Gage that the Float should be• left in a
state of nature, and that docks should be made upon. each side
of it.