o the proportion of
volatile matter present. When the gas is completely given off the
doors are lifted and the charge is pushed out by the ram--a cast-iron
plate of the shape of the cross section of the oven, at the end of a
long horizontal bar, which is driven by a rack and pinion movement and
pushes the block of coke out of the oven on to the wharf or bank in
front where it falls to pieces and is immediately quenched by jets of
water from a hose pipe. When sufficiently cooled it is loaded into
railway wagons or other conveyances for removal. The ram, together
with its motor, and boiler when steam is used, is mounted upon a
carriage running upon a line of rails of about 2 ft. gauge along the
back of the range of ovens, so that it can be brought up to any one of
them in succession.

[Illustration: FIG. 1.--Coppee's Coke Oven.]

In some cases, instead of the small coal being charged through the
roof of the oven and levelled by hand, it is formed into blocks by
being stamped in a slightly moistened condition in a mould consisting
of a bottom plate or peel on a racked rod like that of the ram, with
movable sides and ends. This, when the ends are removed, is pushed
forward into the oven, and the bottom plate is withdrawn by reversing
the rack motion. The moulding box is mounted on a carriage like that
of the ram, the two being sometimes carried on the same framing. The
moulding is done at a fixed station in the centre of the range of
ovens by a series of cast-iron stampers driven by an electric motor.
This system is useful for coals low in volatile matter, which do not
give a coherent coke under ordinary conditions.

Condensing ovens.

In the distilling or by-product ovens the gases, instead of being
burned at the point of origin, pass by an uptake pipe in the roof
about the centre of the oven into a water-sealed collecting trough or
hydraulic main, whence they are drawn by exhausters through a series
of air and water cooled condensers and scrubbers. In the first or
atmospheric condensers the tar is removed, and in the second
ammoniacal water, which is further enriched by a graduated system of
scrubbing with weak ammoniacal liquor until it is sufficiently
concentrated to be sent to the ammonia stills. The first treatment by
scrubbing with creosote or heavy tar oil removes benzene, after which
the permanent gaseous residue consisting chiefly of