1. Sewers.
2. Drains.
These two classes of refuse-charts are often confounded, even in some
official papers, the sewer being there designated the “main drain.” All
sewerage is undoubtedly drainage, but there is a manifest distinction
between a sewer and a drain.
The First-Class Sewers, which are generally termed “main sewers,” and
run along the centres of the first-class streets (first-class alike
from the extent or populousness of such streets), may be looked upon
as underground rivers of refuse, to which the drains are tributary
rivulets. No sewer exists unconnected with the drains from the streets
and houses; but many house-drains are constructed apart from the
sewers, communicating only with the cesspools. Even where houses are
built in close contiguity to a public sewer, and built after the new
mode without cesspools, there is always a drain to the sewer; no house
so situated can get rid of its refuse except by means of a drain;
unless, indeed, the house be not drained at all, and its filth be flung
down a gullyhole, or got rid of in some other way.
These drains, all with a like determination, differ only in their
forms. They are barrel-shaped, made of rounded bricks, or earthenware
pipeage, and of an interior between a round and an oval, with a
diameter of from 2 to 6 inches, although only a few private houses,
comparatively, are so drained. The barrel drain of larger dimensions,
is used in the newer public buildings and larger public mansions, when
it represents a sort of house or interior sewer as well as a house
main drain, for smaller drains find their issue into the barrel-drain.
There is the barrel-drain in the new Houses of Parliament, and in large
places which cover the site of, and are required for the purposes of
several houses or offices. The tubular drain is simply piping, of which
I have spoken fully in my account of the present compulsory mode of
house drainage. The third drain, one more used to carry refuse to the
cesspool than the sewer, but still carrying such refuse to the sewers,
is the old-fashioned brick drain, generally 9 inches square.
I shall first deal with the sewerage, and then with the house and
street drainage.
The sewer is a twofold receptacle of refuse; into it are conveyed the
wet refuse not only of many of the houses, but of all the streets.
The slop or surface water of the streets is conveyed to the sewer by
means of smaller sewers or street-drains running from the “kennel” or
channel to the larger sewers.
In the streets, at such uncertain distances as the traffic and
circumstances of the locality may require, are gully-holes. These are
openings into the sewer, and were formerly called, as they were, simply
gratings, a sort of iron trap-doors of grated bars, clumsily made, and
placed almost at random. On each side of the street was, even into
the present century, a very formidable channel, or kennel, as it was
formerly written, into which, in heavy rains, the badly-scavaged street
dirt was swept, often demanding a good leap from one who wished to
cross in a hurry. These “kennels” emptied themselves into the gratings,
which were not unfrequently choked up, and the kennel was then an utter
nuisance. At the present time the channel is simply a series of stone
work at the edge of the footpaths, blocks of granite being sloped to
meet more or less at right angles, and the flow from the inclination
from the centre of the street to the channel is carried along without
impedimen or nuisance into the gully-hole.
The gully-hole opens into a drain, running, with a rapid slope, into
the sewer, and so the wet refuse of the streets find its vent.
In many courts, alleys, lanes, &c., inhabited by the poor, where there
is imperfect or no drainage to the houses, all the slops from the
houses are thrown down the gully-holes, and frequently enough blood and
offal are poured from butchers’ premises, which might choke the house
drain. There have, indeed, been instances of worthless street dirt
(slop) collected into a scavager’s vehicle being shot down a gully-hole.
The sewers, as distinct from the drains, are to be divided principally
into three classes, all devoted to the same purpose--the conveyance
of the underground filth of the capital to the Thames--and all
connected by a series of drains, afterwards to be described, with the
dwelling-houses.
The _first-class sewers_ are found in the main streets, and flow at
their outlets into the river.
The _second-class sewers_ run along the second-class streets,
discharging their contents into a first-class sewer; and
The _third-class sewers_ are for the reception of the sewage from the
smaller streets, and always communicate, for the voidance of their
contents, with a sewer of the second or first description.
As regards the destination of the sewers, there is no difference
between the Middlesex and Surrey portions of the metropolis. The sewage
is _all_ floated into the river.
The first-class sewers of the modern build rarely exceed 50 inches
by 30 in internal dimensions; the second class, 40 inches by 24; the
third, 30 inches by 18.
Smaller class or branch sewers, from No. 4 to No. 8 inclusive, also
form part of the great subterranean filth-channels of the metropolis.
It is only, however, the three first-mentioned classes which can be
described as in any way principal _sewers_; the others are in the
capacity of branch sewers, the ramifications being in many places very
extensive, while pipes are often used. The dimensions of these smaller
sewers, when pipes are not used, are--No. 4, 20 inches by 12; No. 5,
17-1/2 inches by 10-1/2; No. 6, 15 inches by 9; No. 7, 12 inches by
7-1/2; and No. 8, 9 inches by 6.
These branch sewers may, from their circumscribed dimensions, be looked
upon as mere channels of connection with the larger descriptions; but
they present, as I have intimated, an important part of the general
system. This may be shown by the fact, that in the estimates for
building sewers for the improvement of the drainage of the city of
Westminster (a plan, however, not carried out), the estimated, or
indeed surveyed, run of the first class was to be 8118 feet; of the
second class, 4524 feet; of the third, but 2086 feet; while of the No.
5 and No. 6 description, it was, respectively, 18,709 and 53,284 feet.
The branch sewers may, perhaps, be represented in many instances as
public drains connecting the sewer of the street with the issue from
the houses, but I give the appellation I find in the reports.
The dimensions I have cited are not to be taken as an average size of
the existing sewers of the metropolis on either side of the Thames, for
no average size and no uniformity of shape can be adduced, as there has
been no uniformity observed. The sewers are of all sizes and shapes,
and of all depths from the surface of the streets. I was informed by
an engineering authority that he had often seen it asserted that the
naval authorities of the kingdom could not build a war-steamer, and it
might very well be said that the sanitary authorities of the metropolis
could not build a sewer, as none of the present sewers could be cited
as in all respects properly fulfilling all the functions required.
But it must be remembered that the present engineers have to contend
with great difficulties, the whole matter being so complicated by the
blunderings and mismanagement of the past.
The dimensions I have cited (because they appear officially) exceed the
medium size of the _newer_ sewerage, the average height of the first
class being in such sewers about 3 feet 9 inches.
_Of the width of the sewers_, as of the height, no precise average can
be drawn. Perhaps that of the New Palace main, or first-class sewer, 3
feet 6 inches, may be nearest the average, while the smaller classes
diminish in their width in the proportions I have shown. The sewers of
the older constructions nearly all widen and deepen as they near the
outlet, and this at no definite distance from the river, but from a
quarter of a mile or somewhat less to a mile and more. Some such sewers
are then 14 feet in width; some 20 feet, and no doubt of proportionate
height, but I do not find that the height has been ascertained.
For flushing purposes there are recesses of greater or less width,
according to the capacity of the sewer, where sluice-gates, &c., can be
fixed, and water accumulated.
Under the head of “Subterranean Survey of the Sewers,” will be found
some account of the different dimensions of the sewers.
_The form of the interior of the sewers_ (as shown in the illustrations
I have given) is irregularly elliptical. They are arched at the
summits, and more or less hollowed or curved, internally, at the
bottom. The bottom of the sewer is called the “invert,” from a general
resemblance in the construction to an “inverted” arch. The _best_ form
of invert is a matter which has attracted great engineering attention.
It is, indeed, the important part of the sewer, as the part along which
there is the flow of sewage; and the superior or inferior formation of
the invert, of course, facilitates or retards the transmission of the
contents.
A few years back, the building of egg-shaped, or “oviform” sewers, was
strongly advocated. It was urged that the flow of the sewage and the
sewer-water was accelerated by the invert (especially) being oviform,
as the matter was more condensed when such was the shape adopted, while
the more the matter was diffused, as in some of the inverts of the more
usual form of sewers, the less rapid was its flow, and consequently the
greater its deposit.
What extent of egg-shaped sewers are now, so to speak, at work, I could
not ascertain. One informant thought it might be somewhere about 50
miles.
The following interesting account of the velocities of streams, with
a relativeness to sewers, is extracted from the evidence of Mr.
Phillips:--
“The area of surface that a sewer will drain, and the quantity of water
that it will discharge in a given time, will be greater or less in
proportion as the channel is inclined from a horizontal to a vertical
position. The ordinary or common run of water in each sewer, due from
house drainage alone, and irrespective of rain, should have sufficient
velocity to prevent the usual matter discharged into the sewer from
depositing. For this purpose, it is necessary that there should be
in each sewer a constant velocity of current equal to 2-1/2 feet per
second, or 1-3/4 mile per hour.” Mr. Phillips then states that the
inclinations of all rivulets, &c., diminish as they progress to their
outfalls. “If the force of the waters of the river Rhone,” he has said,
“were not absorbed by the operation of some constant retardation in
its course, the stream would have shot into the Bay of Marseilles with
the tremendous velocity of 164 miles every hour. Even if the Thames
met with no system of impediments in its course, the stream would have
rushed into the sea with a velocity of 80 feet per second, or 54-1/2
miles in an hour.... The inclinations of the sewers of a natural
district should be made to diminish from their heads to their outfalls
in a corresponding ratio of progression, so that as the body of water
is increased at each confluence, one and the same velocity and force of
current may be kept up throughout the whole of them.”
Mr. Phillips advocates a tubular system of sewerage and drainage.
The main sewer, which has lately called forth the most public
attention and professional controversy, is that connected with the
new Houses of Parliament, or as they are called in divers reports and
correspondence, the “New Palace at Westminster.”
_The workmanship in the building of the sewers_ is of every quality.
The material of which some of the older sewers are constructed is a
porous sort of brick, which is often found crumbling and broken, and
saturated with damp and rottenness, from the exhalations and contact
of their contents. The sewers erected, however, within the last
twenty, and more especially within the last ten years, are sometimes
of granite, but generally of the best brick, with an interior coating
of enduring cement, and generally with concrete on their exterior,
to protect them from the dampness and decaying qualities of the
superincumbent or lateral soil.
_The depth of the sewers_--I mean from the top of the sewer to the
surface of the street--seems to vary as everything else varies about
them. Some are found forty feet below the street, some _two_ feet, some
almost level! These, however, are exceptions; and the average depth of
the sewers on the Middlesex side is from twelve to fourteen feet; on
the Surrey side, from six to eight feet. The reason is that the north
shores of the metropolis are above the tide level, the south shores are
below it.
An authority on the subject has said, “The Surrey sewers are bad,
owing principally to the land being below tide level. They were the
most expensively constructed, because, _perhaps_, in that Commission
the surveyors were paid by percentage on the cost of works. When it
was proposed, in the Westminster Commission, to effect a reduction
of four-fifths in the cost, it was like a proposition to return the
officers’ salaries to that extent, if they had been paid in that way.”
The reader may have observed that the official intelligence I have
given all, or nearly all, refers to the “Westminster and part of
Middlesex” Commission, and to that of the “Surrey and Kent.” This is
easily accounted for. In the metropolitan districts, up to 1847, the
only Commission which published its papers was the Westminster, of
which Mr. L. C. Hertslet had the charge as clerk; when the Commissions
were consolidated in 1847, he printed the Westminster and Surrey only,
the others being of minor importance.
I may observe that one of the engineers, in showing the difficulty or
impossibility of giving any description of a _system_ of sewerage, as
to points of agreement or difference, represents the whole mass as but
a “detached parcel of sewers.”
_The course of the sewers_ is in no direct or uniform line, with the
exception of one characteristic--all their bearings are towards the
river as regards the main sewers (first-class), and all the bearings
of the second-class sewers are towards the main sewers in the main
streets. The smaller classes of sewers fill up the great area of London
sewerage with a perfect network of intersection and connection, and
even this network is increased manyfold by its connection with the
house-drains.
There is no map of the general sewerage of the metropolis, merely
“sections” and “plans” of improvements making or suggested, in the
reports of the surveyors, &c., to the Commissioners; but did a map of
subterranean London exist, with its lines of every class of sewerage
and of the drainage which feeds the sewers; with its course, moreover,
of gas-pipes and water-pipes, with their connection with the houses,
the streets, the courts, &c., it would be the most curious and
skeleton-like map in the world.