fifty thousand bushels of cement, three millions
eight hundred and thirty-four thousand bushels
of lime, and four thousand tons of wrought and
cast-iron for the bridges over the streams and
railways. The natural drainage of the marshes
will, of course, be carried under the embankment
in culverts.

This great outfall sewer, which will empty
itself into a covered reservoir at Barking creek,
capable of containing seven millions of cubic
feet of sewage, will not only receive the
combined streams poured into it by the high-level
and low-level sewers just described, but also
another vast flood which will probably be pumped
into it from another line of projected main
intercepting tunnel, called the low-level sewer.
This sewer depends so much upon the project of
a Thames embankment, which has been for some
time under the consideration of parliament, that
Mr. Bazalgette has wisely given up reporting
about it until the great river terrace scheme
shall be decided upon one way or other. Its
course, as laid down on paper, is to hug
the bank of the river from Chelsea through
Westminster, the Strand, Cannon-street,
East-cheap, Tower-hill, Stepney, and Limehouse, to
the river Lea, where it will join the other
intercepting sewers. It will take in, five branches;
from Brentford, Fulham, Victoria-street,
Westminster, the Isle of Dogs, and Hackney marsh;
and as its level will be about thirty-seven feet
below the high level and middle level sewers,
its stream will have to be pumped by
engine-power into the great outfall channel.

The great intercepting sewers on the south-side
of the river Thames are divided into a
high-level tunnel and a low-level tunnel, with an
outfall underground channel.

The high-level tunnel begins at Clapham
Common, and winds its way through Stockwell
and Camberwell to Peckham, where it is joined
by a long fork or branch, called the Effra branch
—an improved substitute for the open Effra
ditch—which comes down from Dulwich. In
cutting this branch, many remarkable fossils have
been found, including remains of crocodiles. The
two tunnels then continue from Peckham through
New Cross, until they end in Deptford creek,
where they are provided with storm overflow
chambers, very similar to those in the north-side
sewers. The whole length of this high-level
sewer is between nine and ten miles; and rather
more than one half, at different points of its
course, is just completed. It begins, like most
of the others, as a circular tunnel about four
feet in diameter, and increases in size here and
there until it ends in a diameter at least ten
feet and a half. When finished, it will cut off
and divert the upland waters which now flood
the low and tide-locked districts. It is estimated
that this intercepting sewer will suck up eighty-two
thousand cubic yards of brickwork, thirty
millions of bricks, two hundred thousand bushels
of cement, four hundred thousand bushels of
lime, seventy-five thousand cubic yards of
concrete, and will require more than half a million
cubic yards of ground to be cut out, and nearly
the same quantity of earth and materials to be
carted.

The low-level intercepting sewer is mapped
out to run from Putney through Battersea,
Brixton, Camberwell, the Old Kent-road, and
across the market gardens to Deptford. It will
be provided with a couple of storm overflow
branches, running into the Thames at Vauxhall
and Deptford, and a north or Bermondsey
branch, which will intercept many sewers
running through that district. At present it can
only be said to exist on paper, although the
contractors have begun the works at Deptford,
where they found the undersoil to be a running
sand, filled with an extraordinary volume of
water. As this end of the low-level sewer will
be at least twenty feet below the end of the
high-level sewer, pumping power will be required,
as on the north side, to raise the stream into the
great outfall tunnel.

The great southern outfall sewer, which may
be regarded as a work second only in extent and
importance to the northern outfall sewer, is
more than half completed. It will pass from
the Deptford pumping station, through Greenwich
and Woolwich under the Erith marshes to
a covered reservoir capable of containing four
millions of cubic feet of sewage, on the river
bank at Crossness Point, beyond Plumstead.

The length of this main tunnel will be about
seven and a half miles, and its diameter about
eleven and a half feet. Its depth from the
surface in many parts is very great, especially
about Woolwich, where the entrance shafts are
like the mouths of huge mines with ladders going
down at different inclinations. Here, the tunnel
has been constructed for some distance, mole-like,
under the ground: most probably without a
large portion of the inhabitants being aware of
its existence or progress. It is estimated that
about half a million cubic yards of ground will
have to be dug out for this channel, and that
about the same quantity of earth and materials
will have to be carted. It will suck up one
hundred thousand cubic yards of brickwork,
thirty-seven millions of bricks, and six hundred
thousand bushels of cement; and when
completed with the other works, it will receive and
carry off the whole of the drainage of that
portion of London which is on the south-side of the
Thames. These southern works, from their
commencement to the present time, have given
weekly employment to upwards of two thousand
men.

The sewage reservoirs on the north-side at
Barking creek, and on the south-side at
Plumstead marshes, will be raised some twenty-one
feet above the level of the outfall sewers, and the
stream will be pumped into them. The final
discharge of the fluid sewage at high-water
—the solid sewage being deposited in the
reservoirs—will take place through covered
channels buried under water, and communicating
with the centre and bottom of the river Thames.
The works have been calculated so as to admit
of extensions as the metropolitan population
expands, and to carry off the sewage of three