aterial must be quenched by water, a
sufficiently delicate operation in itself. The chief use for hot coke
conveyors has been found in connexion with gas works, but attempts have
also been made to provide efficient machinery for the service of coke
ovens of great capacity.

The justification of any kind of machinery must rest on its relative
efficiency and economy. As compared with some other materials the
mechanical handling of hot coke does not realize such a striking
economy; a hot coke conveyor is expensive to build--on account of the
great wear and tear it must be very solidly constructed--and it is
costly in upkeep. Still in large gas works the use of machinery for
treating glowing coke is economically advisable. Exact calculations are
not very easy to make, because while the cost of hand labour in this
department of a gas works is accurately known, the efficiency of
different hot coke conveyors varies. G. E. Stephenson, of the Gathorn
gas works, estimated that a saving of 4-3/4d. per ton had been realized on
each ton of coke conveyed to the yard from the retort house, as against
the same material wheeled in barrows. This saving represented the
difference between the cost of twelve men, who formerly handled the hot
coke with shovels and barrows, and the cost of one conveyor with the
wages of one man to look after it. In an ordinary way one man would rake
out the coke from the retort mouthpiece into a barrow placed underneath,
while a second man quenched the glowing coke with buckets of water, or
better still with a hose. Then the barrow would be wheeled out into the
yard. Obviously this is a slow and relatively expensive method, apart
from the deleterious fumes arising from the quenching of the coke. Some
improvement was effected by the substitution for the old hand-barrows of
cage-like tipping trucks; these are run on narrow gauge rails out of the
retort house and the red-hot coke they contain is quenched by a copious
spray, the truck being placed the while over a grating through which the
surplus water is drained away, under an inverted funnel with an uptake
to carry away the fumes and vapours. These trucks have been hauled, in
lieu of human arms, by endless ropes or even small locomotives.

The earlier hot coke conveyors were of the _pushplate_ type. The
trough, some 27 in. wide, consisted of cast iron sections, while the
pushplates, formed of malleable castings, were attached at a pitch of
24 in. to a