us a taste of his ' reading up,' 'are of two
kinds; first, such as are mechanically
suspended—say earth, chalk, sand, clay, dead
vegetation or decomposed cats; and secondly,
such as are dissolved or chemically combined
—like salt, sugar, or alkali. Separation in the
one case is easy, in the other it involves a
chemical process. If you throw a pinch of
sand into a tumbler of water, and stir it
about, you produce a turbid mixture; but to
render the fluid clear again you have only to
adopt the simple process of letting it alone;
for on setting the tumbler down for awhile, the
particles—which, from their extreme minuteness,
were easily disturbed and distributed
amidst the fluid—being heavier than water,
are precipitated, or in other words, fall to the
bottom, leaving the liquid translucent. This
is what is happening in the larger section of
the reservoir to the chalky water of which
we drank. I think I am correct? ' asked the
speaker, angling for a single ' cheer ' from the
Engineer.

' Quite so,' replied that gentleman.

'Provided the water could remain at rest
long enough—which the insatiable maw of the
modern Babylon does not allow,'—continued
the honourable orator, rehearsing a bit more
of his speech, ' this mode of cleansing would
be perfectly effectual. In proof of which
I may only allude to Nature's mode of
depuration, as shown in lakes—that of Geneva
for instance. The waters of the Rhone enter
that expansive reservoir from the Valais in a
very muddy condition; yet, after reposing in
the lake, they issue at Geneva as clear as
crystal. But so incessant is the London
demand, that scarcely any time can be afforded
for the impurities of the Thames, the Lea, or
the New River to separate themselves from
the water by mere deposition.'

' True,' interjected one of the superintendants.
'It is for that reason that our
water is passed afterwards into the filtering
bed, which is four feet thick.'

' How do you make up this enormous bed?'

' The water rests upon, and permeates
through, 1st, a surface of fine sand; 2d, a
stratum of shells; 3d, a layer of garden
gravel; and 4th, a base of coarse gravel. It
thence falls through a number of ducts into
cisterns, whence it is pumped up so as to
commence its travels to town through the
conduit pipe.'

We were returning to the engine-house,
when Lyttleton asked the Engineer, 'Does
your experience generally, enable you to say
that water as supplied by the nine companies,
is tolerably pure? '

' Upon the whole, yes,' was the answer.

' Indeed! ' ejaculated the orator, sharply.
' If that be true,' he whispered to me, in a
rueful tone, ' I shall be cut out of one of the
best points in my speech.'

' Of course,' continued the Engineer, 'purity
entirely depends upon the source, and the
means of cleansing.'

'Then, as to the source—how many
companies take their supplies from the Thames,
near to, and after it has received the contents
of, the common sewers? '

' No water is taken from the Thames below
Chelsea, except that of the Lambeth
Company, which is supplied from between Waterloo
and Hungerford Bridges; an objectionable
source, which they have obtained an act to
change to Thames Ditton. The Chelsea
Waterworks have a most efficient system of
filtration; as also have the Southwark and
Vauxhall Company; both draw their water
from between the Red House, Battersea, and
Chelsea Hospital. The other companies do
not filter. The West Middlesex sucks up
some of Father Thames as he passes Barnes
Terrace. Except the lowest of these sources,
Thames water is nearly as pure as that of
other rivers.'

' Perhaps it is,' was the answer; ' but the
unwholesomeness arises from contaminations
received during its course; we don't object to
the " Thames," but to its " tributaries," such as
the black contents of common sewers, and the
refuse of gut, glue, soap, and other nauseous
manufactures; to say nothing of animal and
vegetable offal, of which the river is the sole
receptacle. Brande shows that, while the
solid matter contained in the river at
Teddington is 17.4, that which the water has
contracted when it flows past Westminster
is 24.4, and the City of London, 28.0.'

' But,' said the Engineer, ' these adulterations
are only mechanically suspended in the
fluid, and are, as you shall see presently,
totally separated from it by our mode of
filtration.'

'Which brings us to your second point,
as to efficient cleansing; you admit that
without filtration this is impossible, and also
that only three companies filter; the deduction,
therefore, is that two-thirds of the
water supplied to Londoners is insufficiently
cleansed. This indeed, is not a mere
inference; we know it for a fact, we see it in
our ewers, we taste it out of our caraffes.'

' But this does not wholly arise from the
inefficient filtration of the six companies,'
returned an officer of this Company, ' the
public is much to blame—though, when
agitating against an abuse, it never thinks of
blaming itself. Half the dirt, dust, and
animalculæ found at table are introduced
after the water has been delivered to the
houses. Impurity of all sorts finds its way
into out-door cisterns, even when covered,
and few of them, open or closed, are often
enough cleansed. In some neighbourhoods
water-butts are always uncovered, and hardly
ever cleaned out. The water is foul, and the
companies are blamed.'

' The blame belongs to the system,' said the
barrister. ' Domestic reservoirs are not only
an evil but an unnecessary expense. Besides
filth, they cause waste and deficient supply:
they should be abolished; for continuous