Having estimated the gross quantity of wet house-refuse produced
throughout London in the course of the year, and explained the two
modes of removing it from the immediate vicinity of the house, I will
now proceed to set forth the _quantity_ of wet house-refuse matter
which it has been _ascertained_ is removed with the contents of London
sewers.
An experiment was made on the average discharge of sewage from the
outlets of Church-lane and Smith-street, Chelsea, Ranelagh, King’s
Scholar’s-pond, Grosvenor-wharf, Horseferry-road, Wood-street,
King-street, Northumberland-street, Durham-yard, Norfolk-street,
and Essex-street (the four last-mentioned places running from the
Strand). The experiments were made “under ordinary and extraordinary
circumstances,” in the months of May, June, and July, 1844, but the
system is still the same, so that the result in the investigation as
to the sewage of the year 1844 may be taken as a near criterion of the
present, as regards the localities specified and the general quantity.
The surface drained into the outlets before enumerated covers, in its
total area, about 7000 acres, of which nearly 3500 may be classed as
urban. The observations, moreover, were made generally during fine
weather.
I cannot do better by way of showing the reader the minuteness with
which these observations were made, than by quoting the two following
results, being those of the fullest and smallest discharges of twelve
issues into the river. I must premise that these experiments were
made on seven occasions, from May 4 to July 12 inclusive, and made at
different times, but generally about eight hours after high water. In
the Northumberland-street sewer, from which was the largest issue, the
width of the sewer at the outlet was five feet. In the King-street
sewer (the smallest discharge, as given in the second table) the width
of the sewer was four feet. The width, however, does not affect the
question, as there was a greater issue from the Norfolk-street sewer of
two feet, than from the King-street sewer of four feet in width.
+------------------------------------------------
| NORTHUMBERLAND STREET.
+---------+-----------------+--------------------
| | Velocity per | Quantity discharged
| Date. | second. | per second.
+---------+-----------------+--------------------
| | Feet. | Cubic Feet.
| +-----------------+--------------------
| May 4 | 4·600 | 10·511000
| „ 9 | 4·000 | 6·800000
| June 5 | 4·000 | 6·800000
| „ 10 | 4·600 | 10·350000
| „ 11 | 4·920 | 12·300000
| „ 16 | 3·600 | 5·940000
| July 12 | 2·760 | 3·394800
+---------+-----------------+--------------------
| | | 56·095800
+---------+-----------------+--------------------
| Being Mean Discharge |
| per second | 8·013685
| Ditto per 24 hours | 692382·
+---------------------------+--------------------
| KING STREET.
+---------+-----------------+--------------------
| May 4 | ·147 | ·021756
| „ 9 | ·333 | ·079920
| June 5 | ·170 | ·020400
| „ 10 | ·311 | ·064688
| „ 11 | ·300 | ·048000
| „ 16 | ·101 | ·004040
| July 12 | ·103 | ·008240
+---------+-----------------+--------------------
| | | ·247044
+---------+-----------------+--------------------
|Mean Discharge per second | ·035292
| Ditto per 24 hours| 3049·
+---------------------------+--------------------
Here we find that the mean discharge per second was, from the
Northumberland-street sewer, 692,382· cubic feet per 24 hours, and from
the King-street sewer, 3049 cubic feet per 24 hours.
The discharge from the principal outlets in the Westminster district
“being the mean of seven observations taken during the summer,” was
1,798,094 cubic feet in 24 hours; the number of acres drained was 7006.
_The mean discharge per acre, in the course of 24 hours, was found to
be about 256 cubic feet, comprising the urban and suburban parts._
The sewage, from the discharge of which this calculation was
derived--and the dryness of the weather must not be lost sight of--may
be fairly assumed as derived (in a dry season) almost entirely from
artificial sources or house drainage, as there was no rain-fall,
or but little. “_Supposing, therefore_,” the Report states, “_the
entire surface to be urban, we have 540 cubic feet as the mean daily
discharge per acre_. If, however, the average be taken of the first
eight outlets, viz., from Essex-street to Grosvenor-wharf inclusive,
which drain a surface wholly urban, the result is 1260 cubic feet per
acre in the 24 hours. This excess may be attributed to the number
of manufactories, and the densely-populated nature of the locality
drained; but, as indicative of the general amount of sewage due to
ordinary urban districts, the former ought perhaps to be considered the
fairer average.”
It is then assumed--I may say officially--that the average discharge
of the urban and suburban sewage from the several districts included
within an area of 58 square miles, is equal to 256 cubic feet per acre.
Sq. Miles.
The extent of the jurisdiction included
within this area is, on the north side of
the Thames 43
And on the Surrey and Kent side 15
Cubic Feet.
The ordinary _daily_ amount of
sewage discharged into the river on
the north side is, therefore 7,045,120
And on the south side 2,457,600
---------
Making a total of 9,502,720
Or a quantity equivalent to a surface of more than 36 acres in extent,
and 6 feet in depth.
This mass of sewage, it must be borne in mind, is but the _daily_
product of the sewage of the more populous part of the districts
included within the jurisdiction of the two commissions of sewers.
The foregoing observations, calculations, and deductions have supplied
the basis of many scientific and commercial speculations, but it must
be remembered that they were taken between seven and eight years ago.
The observations were made, moreover, during fine summer weather,
generally, while the greatest discharge is during rainy weather. There
has been, also, an increase of sewers in the metropolis, because an
increase of streets and inhabited houses. The approximate proportion
of the increase of sewers (and there is no precise account of it) is
pretty nearly that of the streets, lineally. Another matter has too, of
late years, added to the amount of sewage--the abolition of cesspoolage
in a considerable degree, owing to the late Building and Sanitary
Acts, so that fæcal and culinary matters, which were drained into the
cesspool (to be removed by the nightmen), are now drained into the
sewer. Altogether, I am assured, on good authority, the daily discharge
of the sewers extending over 58 square miles of the metropolis may be
now put at 10,000,000 cubic feet, instead of rather more than nine and
a half millions. And this gives, as
Cubic Feet.
The annual amount of discharge
from the sewers 3,650,000,000
The total amount of wet house-refuse,
according to the calculation
before given, is 3,820,000,000
-------------
Hence there remains 170,000,000
Sq. Miles.
Now it will be seen that the total area
from which this amount of sewage is said
to be drained is 58
But the area of London, according to
the Registrar-General’s limits, is 115
So that the 3,650,000,000 cubic feet of sewage annually removed from
58 square miles of the metropolis refer to only one-half of the entire
area of the _true_ metropolis; but it refers, at the same time, to
that part of London which is the most crowded with houses, and since,
in the suburbs, the buildings average about 2 to the acre, and, in
the densest parts of London, about 30, it is but fair to assume that
the refuse would be, at least, in the same proportion, and this is
very nearly the fact; for if we suppose the 58 miles of the suburban
districts to yield twenty times less sewage than the 58 miles of the
urban districts, we shall have 182,500,000 cubic feet to add to the
3,650,000,000 cubic feet before given, or 3,832,500,000 for the sewage
of the entire metropolis.
It does not appear that the sewage has ever been weighed so as to
give any definite result, but calculating from the weight of water (a
gallon, or 10 lbs. of water, comprising 277·274 cubic inches, and 1 ton
of liquid comprising 36 cubic feet) the total, from the returns of the
investigation in 1844, would be
Tons.
Quantity of sewage _daily_ emptied into the Thames 278,000
Ditto Annually 101,390,000
In September, 1849, Mr. Banfield, at one time a Commissioner of Sewers,
put the yearly quantity of sewage discharged into the Thames at
45,000,000 tons; but this is widely at variance with the returns as to
quantity.