introduce a variety of mechanical improvements in
the manufacture and distribution of gas, that have
fixed his name in the foremost rank of gas-engineers.
In the early days of gas-lighting, the
manufacture was very rude, and was long watched
with fear by the public and the government
inspectors. Sir William Congreve, appointed to
make a report on the state of the metropolitan
gas-works in 1822, saw two large canvas bags in
some works at Whitechapel, of about fifteen
thousand cubic feet each, which were for some
time used as gas-holders near to a blacksmith's
forge. He hints at the direful consequences
which might ensue "were the tar to be
discharged and inflamed, like an emission of a
large quantity of burning lava from an artificial
volcano."

Those black volcanoes, the gas-holders
(originally called gasometers), are now vastly
increased in size, and improved until little is left
for further alteration. When a deputation from
the Royal Society, with Sir Joseph Banks at its
head, visited the gas-works of the Chartered
Company at Westminster in 1814, they strongly
recommended government to prevent the
company constructing gas-holders exceeding six
thousand cubic feet in capacity, to be confined in
very strong buildings. The largest gas-holders
in London are now constructed to hold from a
quarter of a million to half a million of cubic
feet each, and they stand out boldly, like
gigantic iron vats, towering above the walls of
the gas-yards. The importance of such reservoirs,
containing a night's supply of gas in advance,
can hardly be overrated by any man who
tries to imagine the condition of London
suddenly plunged into total darkness.

The manufacture of gas, although it includes
many beautiful scientific processes, is not, on
the whole, a sightly operation. What is not
seen may be refined and interesting; but what
is seen decidedly savours of pandemonium.
There are huge caverns of black coal, huge
caverns of red-hot coke, and a row of roaring
fiery ovens, which sooty men are constantly
feeding with coal thrust in out of long iron
scoops. The lids of these ovens, or retorts, are
generally heated to a white heat, and the men
who lift them off and put them on, have their
hands protected with thick gauntlet gloves.
After the coal has been distilled, as it is called,
the red-hot coke is raked out, either into coke-
vaults, or iron barrows. The spirit of the coal
rises up black pipes, like infernal organ pipes,
leading from each oven into a tube, running the
whole length of the retort-house, called the
hydraulic main, which they reach by a curved dip
pipe. The hydraulic main, as its name implies,
is half-filled with water, and the end of the dip-
pipe passes through this water to the depth of
about four inches. The gas from the retorts
flows down the dip-pipe, and bubbles up by its
lightness through the water till it rests in that
part of the main above the surface of the liquid,
depositing its tar in its progress. The water,
which gradually changes its character with this
deposit, and becomes nearly all tar, locks the
gas in the upper part of the main, and only
suffers it to pass off through the purifiers. These
purifiers, partly mechanical, partly chemical,
relieve the gas from the vapours of tar, ammonia,
sulphuretted hydrogen, and carbonic acid, and
allow it to enter the gas-holder or reservoir,
pure enough for the ordinary purposes of lighting.

The gas-holder is cylindrical in shape, made
of plate-iron, covered at the top, but having no
bottom. It is inverted over a cistern of water,
and both the inlet and outlet pipes for the gas
have their mouths above the surface of this
water. When the purified gas flows in, it raises
the gas-holder, and when it is pressed out into
the main pipes, the holder sinks. The gas
having a tendency to rise and not to flow, is
always sent through the mains by a certain
degree of pressure acting on its source.

The London gas supply is now furnished by
thirteen gas companies, if we exclude the Brentford,
Wandsworth, Crystal Palace district, and
the two Woolwich companies, which light only
limited portions of the metropolitan area. These
thirteen companies— ten on the north side of
the river and three on the south side— represent
a capital of a little over five millions sterling,
and their dividends, on non-preferential shares,
have lately shown an average of something like
seven per cent per annum. No trading
corporations have been more closely " inspected" by
government, and, at present, the regulation of
the supply of gas is held to be in the hands of
the Home Secretary. " In the year 1829,"
says Mr. Samuel Hughes, F.G.S., to whom I
am indebted for much information on this subject,
" gas was sold in London at fifteen
shillings a thousand cubic feet, and at this price
it was so impure, that I have seen test-papers,
which had been preserved from that date,
coloured and stained as black as ink, owing to
the presence of sulphuretted hydrogen. At the
present day, gas is sold in the city of London
at four shdlings per thousand cubic feet, without
meter rent, and it is so pure that scarcely
a trace of sulphuretted hydrogen can be
detected in it, and the test-papers for ascertaining
this impurity are rarely discoloured in the
smallest degree."

We have now, within the metropolitan area,
twenty-three gas manufacturing stations, and
six gas-holder stations, used solely for storing
gas. The total length of mains laid down by
the thirteen companies in underground London,
is seventeen hundred and fifty miles, besides
about four hundred and fifty miles of branch
service-pipes. The house service-pipes, in
addition to this, must be at least eight thousand
miles long.

The total number of London public street-
lamps supplied with gas is thirty-seven thousand
seven hundred and twenty-eight, the average
distance from each other being seventy-five
yards.

The consumption of gas now is at least double
what it was ten years ago; and the annual
quantity manufactured in London is about eight