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16
Table II.—continued.

Water Supply.
The water supply of this parish is derived from the following sources,
viz.:—The Thames, the Wandle, numerous shallow wells, a few deep
wells and Artesian borings, the Southwark and Vauxhnll and the Lambeth
Water Companies. I have made careful examination of the qualities
of samples of these different waters, with a view to the determination
of their value for dietetic and general domestic use. The results I
present in a tabulated form. It will be perhaps desirable, in order to
show its import, to preface the examination of this table by some
remarks explanatory, 1st, of what the impurities of water consist; and,
2ndly, of the relation which the use of impure water bears to health and
disease; and then to offer some observations on the qualities of the
waters of this parish, and on the means of obtaining a proper and
adequate supply.
1st. The usual impurities of water are inorganic and organic matters,
either chemically dissolved or mechanically suspended. The former
comprise certain salts, principally of soda, potash, lime, and magnesia,
derivable from and consequently varying with the nature of the soil
through which the water percolates; and of certain gases, chiefly
carbonic acid, derived from the atmosphere or resulting from saline
decomposition. These salts, when in excess, give to a water a medicinal
action (e. g , the Epsom springs); and those of lime and magnesia the
quality so well known to housewives as hardness. The latter consists
of the lowest forms of animal and vegetable organisms, living and dead,
and the soluble products of their decay; and very generally, in the
shallow wells of populous towns, of a notable amount of animal matter
in solution, and of substances indicative of the presence of the soluble
contents of cesspools. These substauces are ammonia and nitric acid,
which represent the first stages of transformation of animal products
into their ultimate elements. The slight straw colour which a water often
possesses (and which is referred to in the Table) denotes the presence of
organic matter almost invariably. When present this is readily seen, if
the water be examined in bulk; sometimes it is scarcely noticeable
until placed against a white surface, such as a sheet of writing paper.
2ndly. There is abundance of evidence to shew that the use of impure
water plays an active part both in the causation and the propagation of