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10
Let us examine the soil occupied by the inhabitants of Shoreditch. The sections
which accompany this Report supply a generally correct illustration of the
geological structure of the district. The section made from the borings executed in
the construction of the Artesian well at the workhouse, exhibits all the strata down to
the great chalk-bed. Accounts that have been furnished to me of other borings made
in different parts of the Parish show none but unimportant variations in the upper
strata of coloured clays and sands. The strata which are of the greatest interest in a
sanitary point of view are those which form the outer crust or surface. These strata
exhibit considerable variety in their disposition in different localities. We are chiefly
concerned with the soil to the depth of thirty feet. Proceeding from the surface,
we have a bed of variable thickness, commonly called "made earth." The mode in
which it is "made" deserves serious attention. It is strictly an artificial stratum. The
proportion of "virgin soil" to that of common earth is now reduced to a very insignificant
amount. The great bulk is made up of the accumulations of refuse of every
kind; some brought from a distance and deliberately deposited by builders and roadmakers
who had excavations to fill up, and by scavengers, nightmen, and everybody
who had useless and offensive materials to get rid of. This upper stratum, so constituted,
has been further polluted, and its noxious qualities intensified by innumerable
perforations for cesspools, and constant saturation from defective sewers and drains,
the poisonous exudations from gas-pipes, and every conceivable abomination, resulting
from the offscourings of a population of 125,000 souls. This layer of foul earth, or
the Pest-Stratum, as it may be most appropriately called, varies in thickness from one
or two feet to sixteen or more. It lies upon the gravel, the next stratum. This layer
is also irregularly disposed. It varies in thickness; it extends, in some places which I
have examined, or of which I have authentic information, to a depth of 27 or 30 feet;
in other places it is much shallower. The clay, which is immediately beneath, follows
of course, the corresponding irregularities. The uneven disposition of the upper
surface of the clay is attended by this peculiarity: it forms in various places
hollows or basins, filled with gravel; these basins more or less completely isolate
the portions of gravel they contain from the general bed of gravel of the district.
This arrangement has an important effect upon the drainage and surface-water
supply. Rain falling on the surface above these clay pits, or basins, percolates through
the upper pest-stratum and the gravel, and collects at the bottom of the basin, where
it is retained by the impermeable nature of the clay. If a well is dug into the gravel
of such a basin, it will have a water-supply measured in quantity by the superficial
area of the gathering-ground, the rain-fall, and the capacity of the basin, and affected
in quality by the accidental character of the ingredients composing the upper foul