The Sun.
London, England, 1865-04-04 00:00:00

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THE SUN, LONDON, TUESDAY EVENING, APRIL 4, 1865.

GREAT FIRE IN LEICESTER-SQUARE.
SALE OF THE SALVAGE STOCK.

engineer, Mr. Bazalgette. This intercepting system
consists of three great main lines of sewers, or rather
tunnels, which run from the extreme west to the
extreme east of the metropolis, and which are laid at
right angles to all existing sewers and a little.below
their levels, so as to intercept their contents and
convey them to an outfall 14 miles below London-
bridge. As large a proportion of the sewage as
practicable is by this means carried away by gravi-
tation, and for the remainder a constant discharge
is effected by pumping. At the outlets the sewage
is delivered into reservoirs situate on the banks of
the Thames, and placed at such a level as will en-
able them to discharge into the river at or about the
time of high water. By this arrangement the sew-
age is not only at once diluted by the large volume
of water in the Thames at high water, but is also
carried by the ebb tide to a point in the river 26
miles below London-bridge, and its return by the
following flood tide within the metropolitan area is
effectually prevented. A series of experiments has
demonstrated that the delivery of sewage at high
water into the river at any point is equivalent to its
discharge at low water 12 miles lower down the
river ; therefore the construction of the 12 miles of
sewer to Barking, so laid as only to discharge there
at high water, is virtually equal to taking the sew-
age to a distance of 24 miles from London. Before
these sewers were built, however, many subjects had
to be carefully considered—such as the population,
their habits, water supply, &c., the incline at which
the sewers should be laid, and the rainfall to be pro-
vided for. The quantity of sewage flowing from a
given population varies but little from the water
supply with which that population is provided. The
water supply to various parts of London in 1856
varied from 20 to 25 gallons per head per diem ; ,
but a more liberal supply is contemplated, and that
supply is likely to be further augmented by an in-
crease in the population in districts not then wholly
built upon. It has been ascertained that a district
of average density of population, when wholly built
upon, contains 30,000 people to the square mile, so
that in districts containing that, or more than that,
number of people to the square mile the numbers have
been ascertained and provided for ; but in districts
where the population is below that number provision
has been made for an increase of population up to
30,000 people to the square mile, except over the
outlying districts, where provision has been made
for a population of only 20,000 to the square mile.
An improved water supply, equal to 5 cubic feet or
31+ gallons per head of the ,contemplated increased
population, has also been anticipated.
In providing for the rainfall an averagewas taken
of several years, which shows that in London there
are no less than 155 days in the year in which rain
falls, though out of thisnumber there are only about
25 on which the quantity has amounted to a quarter
of an inch in depth in the 24 hours. But there are
every year exceptional cases of heavy and violent
rain-storms, and these have measured one inch, and
sometimes even as much as two inches in the hour.
These exceptional storms, however rare their occur-
rence, have been provided for by the construction of
overflow weirs at the junctions of the intercepting
sewers with the main valley lines, which act as
safety-valves in times of storm. On such occasions
the surplus waters will be largely diluted, and, after
the intercepting sewers are filled, will flow over the
weirs,. and so by their old channels into the Thames.
To carry out all these works three peat main lines
of intercepting sewers have been necessary—a high,
a middle, and a low level sewer—on each side of the
Thames. It is the low level at the southern outfall
which the Prince opens to-day, and all the works
are now complete, save only the northern low level,
which, as having to run under the Thames Em-
bankment, cannot, of course, be yet constructed.
This northern lowlevel sewer, however, only diverts
about 1-7th part of the northern sewage, so that
virtually from this day forth the Thames may be
said to be tolerably pure. It can never be made as
clean and sparkling as in bygone times, but at least
we may be certain that it will never again become
offensive.

STA 3G and MANTLE respectfully announce tt their
numerous customers and the public that they are now SELL-
ING OFF, at a farther immense r, duo ion. the remaining
portion of the SALVAGE STOCK of Silks, Shawls, Mantles,
Dresses, Calicoes, Ribbons, Hosiery, Trimmings, dm., which
must be immediately cleared to make room for the new
Spring Goods. Doors open at Ten o'clock

The High Level Sewer at the north side of the
river commences with a small drain at Hampstead-
hill. It is about seven miles long, drains an area of
about 10 square miles, and intercepts the sewage of
Hampstead, part of Kentish-town, Highgate, Hack-
ney, Clapton, Stoke Newington, and Holloway. A
portion of the district adjoining the Hackney-
marshes is so low that it was necessary to drain it
through a branch passing into the Low Level Sewer.
The form of this sewer is mostly circular, and varies
in size from 4ft. in diameter to 9ft by 12ft., and its
fall is very rapid. Much property had to betunnelled
under in its construction. One house was actually
underpinned and placed upon iron girders through
the cellar without any further disturbance to the
house. At another part it had to be taken under
the New River, and again through the embankment
of the Great Northern Railway. One of the worst
difficulties, however, was getting it under Sir George
Duckett's Canal, where the crown of the arch of
the sewer is only 24 inches from the water in the
canal. The bottom of the canal and the top of the
sewer are here formed of iron plates and girders,
with a thin coating of puddle between, and no leak-
age has yet taken place or is likely to occur. This
instance of careful tunnelling is, however, far from
being the only one, or even the most difficult. One
line of tunnel, from Kennington Church to the Old
Kent-road, runs a distance of I,oooft. close under
a row of houses, the top of the tunnell being only
from 10ft. to 12ft. below the surface, and its
diameter is about 10ft. The water was pumped out
of the sand for this length of tunnel at the rate of
about 8,000 gallons per minute. The same sewer
was carried, through similar soil, under the Grand
Surrey Canal, and within Bft. of the water in it ;
and again under the same canal in the Deptford
Lower-road, where the distance between the top of
the tunnel and the water in the canal was only 6ft.
4in., the whole of the soil being gravel and sand,
with lft. of puddle in the bottom of the canal.
In the Caledonian-road the 'Regent's Canal was
also tunnelled under, the distance between the top
of the tunnel and the water in the canal being only
2ft., so that the miners could hear the barges as
they passed over their heads scrape against the
ground ; this was, however, executed in clay.
Another tunnel has been formed 33ft. under the
rails of the West London Railway, and under the
Kensington Canal. The sewers were constructed
under the London and Brighton, the North Kent,
and other railways without any interruption to the
continuous traffic on them even for an hour. Per-
haps, however, the most curious instance of success-
ful engineering was shown in taking the Middle
Level Sewer over the Metropolitan (or subterranean)
Railway by a wrought-iron aqueduct, 150 ft. span,
weighing no less than 240 tons ; the depth of con-
struction between the underside of the aqueduct and
the inverts of the double line of sewers being only
2 inches. As the traffic on the railway could not
be stopped during the construction of the aqueduct,
which is actually there only a few inches above the
engine chimneys, the structure was built upon a
stage at a height of sft. above the intended level,
and was lowered into place by means of hydraulic
rams. This stage was necessarily of great strength,
and the sewers were formed by wrought-iron plates
rivetted together.
The Northern Middle Level Sewer drains an area
of 17i square miles. It commences near the Har-
row-road at Kensal-green, passes under the Pad-
dington Canal into the Uxbridge-road at Notting-
hill, along Oxford-street, Hart-street, Liquourpond-
street, and across Clerkenwell-green ; thence by
way of Old-street-road to High-street, Shoreditch,
along Church-street, Bethnal-greeiltroad, and Green-
street; under the Regent's Canal and the North
London Railway, to a junction with the High Level
Sewer at the Penstock-chamber at Bow. The Low
Level Sewer, besides intercepting the sewage from
the low level area, which contains 11 square miles,
r is also the main outlet for a district of, about i 4/