The Sun.
London, England, 1864-12-06 00:00:00

Naval and Military Intelligence.

The deepening of the steam basin of Portsmouth
dockyard by manual labour, with the spade and
barrow, under contract, is being proceeded with as
rapidly as circumstances will permit. The excava.
tion varies from about Eft. to 2ft. in depth; and the
result, when the work is finally completed, will be
to give the basin a uniform depth of 291 t. over its
floor at ordinary spring tides. During the time the
basin is being kept dry, to allow of the necessary
excavation being made to give it this increased
depth, advantage is being taken by the authorities
of the opportunity to lower the inverts at the en-

trances to the dock connected with the basin—Nos.
7,8, and 11. No. 7 dock is having its invert lowered
to 27ft. —that is to say, 2ft. above the new level of
the steam basin new floor. This will give it the
same depth of water as now exists over the invert
of No.lo, or the Warrior dock, at present the largest
in Portsmouth yard. No. 7 was originally con-
structed as a separate dock, having its entrance from
the steam basin. On the plans being decided upon,
however, some years afterwards for No. 10 dock, it
was determined to make the latter a continuation
of No. '7, and by this means obtain a south as well
as north entrance to the steam basin from the bar-
bour, with the additional advantages of greater.
depth of water and readier access. As the new dock
was of larger dimensions in every way than No. 7
the unavoidable result was that a great difference
existed in the depth of the new channel of entrance
formed to the steam basin by this junction of the
two docks, which, as our ships of war increased in
size, power of engines, arid draught of water, could
not fail to prove a bar to the efficiency of the steam
basin, too serious to be allowed to exist. The time
has'now arrived for its removal, and the lowering
of the invert of No. 7 to the level of that of No.
10, at the opposite end of the channel, is the
first step in the matter taken by the auV,o
rities. The second and final step, the lowering of
the floor of No. 7, which is now oft above that of
No. 10, will follow immediately on the completion
of the deepening of its invert. These two docks
aro divided by a caisson at their junction, and
with this caisson remuvtd they form cue long dock
and channel to the steam basin of 670 ft in length.
This deck or channel in the No. 10 portion is 80ft.
wide between the entrance-gate piers at the coping,
100 ft. wide at the top of the lico of coping, and
4011. wide on the floor line. In the No. 7 portion
the same measurements are respectively 80ft.,
100 ft., and 35ft. No. 8 dock is 34611. Gin. in
length from the casson to the head of the dock at
the coping. It is 70ft. wide (at present) between
the entrance-gates piers at the coping, 80ft. at the
top of the line of coping, and 33ft. on the floor line.
Its invert is now being lowered to an equal depth
with Nos. 7 and 10, and its depth of flooring will
follow with No. 7. No. 11 dock, now constructing
by Messrs. George Smith and Co., of Pimlico, is
also having its invert lowered from 22ft. 9in. to
27ft., the depths on Nos. 7,8, and 10. This invert
of No. 11 was the commencement of a dock designed
many years since, but it now must form the en-
trance to an enlarged dock, to the width and depth
of which it must be adapted. The naval estimates
for 18645 fix the cost of lowering this invert and
altering the caisson at £4,494. The dock; when
completed, will be sufficiently capacious to receive
the Minotaur class of ship, providing that the pre-
sent intentions of the Admiralty engineers
.to im-
prove the approaches are carried into effect. The
Steam Basin into which all these docks open is as
nearly as possible in the shape of a ship's rudder,
the after part, or shoulder of the rudder, forming
the northern extremity of the present boundary of
Portsmouth dockyard. It was formally opened
in the presence of her Majesty on the 25th of
May, 1848, Colonel Irvine, C. 8., setting the last
stone ; Mr Rolt, the present chairman of the Thames
Ironworks Engineering and Shipbuilding Com-
pany, being the contractor. It has a length of jetty
on its east face of 679 ft., on its south face of 460 ft.,
on its west face of 950 ft., and on its north face or
shoulder of 560fc. ; 2,500 men were constantly en.
gaged on the work from first to last ; and the quan-
tities of material consumed were 1,155,208 cubic ft•
of stone, 7,696,000 bricks, and 735,700 cubic feet of
Memel and beech timber. In excavating it 984,500
tons of earth were removed. In excavating the floor
of the basin at the present time to increase the depth
of water a considerable number of blocks of atone
have been recovered which had evidently fallen into
the excavated basin from the barges when its walls
were completing, and have remained ever since be-
low the surface of the basin floor. A large number
of pile heads have also been laid bare by the new
excavations, and these will, as a matter of course,
have to be cut down to the new level. The Steam
Basin and its connecting docks referred to is the
only place in which the authorities of Portsmouth
I yard can efficiently refit or repair the iron or other
large ships of her Majesty's navy. Their limited
capabilities have been much felt since the introduc
tion of screw frigates and lincoof-battle ships, and
this has induced the authorities not only to make
arrangements for the extension of Portsmouth yard
which has been the subject of special legislation,
but also to deepen the floors and entrances of the
existing docks and basin in order to utilise them as
far as may be possible for future service. The ex.
isting establishment at Portsmouth, to say nothing
of its absurdly incongruous arrangement, will be
entirely put in the shade by the additions it will
receive in the works now about to commence. The
present extent of Portsmouth dockyard (including
all official residencies, &c., and everything, in
is only 115 acres.
fact,Bu within
t the
eex the
tens ouiobnwn y walls),idlal,riat
the
efirat instance alone,
comprise 177 acres. To efficiently carry on the
onerous duties cf this work Mr H. Wood, who has
been for many years Government Clerk of the
Works, and
Assistant
of Civiler has been,pro-
moted
to the
Eg Engineer,
Superintending e Civil Engineer,
and another appointment has been made of an As-
, sistant Civil Engineer.
rank

The screw corvetteCadmus, 21, 400 horse power,
got up steam yesterday in Chatham harbour, along-
side the dockyard, for the purpose of testing the
working of her boilers and machinery sink, the al-
teration and repairs effected by the engineer depart-
ment. Her engines and screw worked satisfactorily,
the propeller being a new Griffith screw, which has
been supplied to her in lieu of the old Admiralty