Coke is produced by the partial burning of coal, in the same way
that charcoal is from wood. The great source of coke is the gas
manufactory, where it is sold in large quantities, being the result
left in the retorts after the gas has all been driven off; but the
consumption of coke by locomotive engines, &c., where coal would
not be admissible on account of the smoke produced, has become so
great that it is necessary to burn coals for its production; this
is done by a range of ovens fitted up for that purpose, having iron
doors which can be closed to any extent required so as to regulate
the draught of air. Dr. Ure gives the following in his account of
the coke ovens belonging to the London and North Western Railway
Company:--“An excellent range of furnaces for making a superior
article of coke for the service of the locomotive engines of the
London and Birmingham Railway Company, has been erected at the Camden
Town Station, consisting of eighteen ovens, in two lines, the whole
discharging their products of combustion into a horizontal flue
which terminates in a chimney-stalk one hundred and fifteen feet
high. Each alternate oven is charged, between eight and ten o’clock
every morning, with three-and-a-hall tons of good coals, a wisp of
straw is thrown in on the top of the heap, which takes fire by the
radiation from the dome, which is in a state of dull ignition from
the preceding operation, and inflames the smoke then rising from the
surface by the reaction of the hot sides and bottom upon the body of
the fuel, in this way the smoke is consumed at the very commencement
of the process, when it would otherwise be most abundant. The coke
being perfectly freed from all fuliginous and volatile matters by
a calcination of upwards of forty hours, is cooled down to moderate
ignition by sliding in the dampers and sliding up the doors, which
had been partially closed during the latter part of the process.
It is now observed to form prismatic concretions, somewhat like a
columnar mass of basalt. These are loosened by means of iron bars,
lifted out upon shovels furnished with long iron shanks, which are
poised upon swung chains with hooked ends, and the lumps are thrown
upon the pavement, to be extinguished by sprinkling water upon them
from the rose of a watering can, or they may be transferred into a
large chest of sheet iron set on wheels, and then covered up. Good
coals, thus treated, yield eighty per cent. of an excellent, compact,
glistening coke, weighing fourteen cwt. per chaldron.”