568 GEOLOGY OF OHIO. 
crown of the vault. They are built of the best quality of fire-brick, 
the arch being about 3 feet thick, resting on a foundation of masonry. 
A round hole, 12 inches in diameter, is left in the crown of the arch 
for charging the coal, and for the escape of the waste gases. A circular 
cast-iron plate is provided by which this hole may be sealed when the 
operation of coking is completed. Another opening is left in front 
about 30 inches square, which is lined with an iron frame, and by which 
the coke is discharged. The bottom of the oven is formed of a bed, 
3 feet thick, of ashes and slag beaten down compactly, upon which a 
floor of fire-brick is placed, inclining slightly toward the front door. 
The ovens are built back to back in order to facilitate their 
charging from the elevated track, which is supported at intervals by 
masonry piers, so that the weight of the cars does not bear upon the 
furnaces. <A wall of masonry forms the front faces of the furnaces, and 
the spaces between them and the ovens is closely filled with ashes. 
The walls are strongly built and bound together by tie-rods to prevent 
their displacement by the expansive action of the heat. 
Water conveyed by pipes is convenient to each oven for the 
quenching of the coke as it is drawn from the oven. ‘This may be said 
here to be a most important adjunct to every coking establishment, as 
water is absolutely necessary to extinguish the fire when the coking 
operation is completed. 
The bee-hive oven of this character as usually built in the United 
States costs from 300 to 500 dollars per oven, according to the material 
and method of construction. 
The operation is as follows: A charge having been removed from 
the oven, the walls are at a very dull red heat, the temperature having 
been reduced during the cooling and discharge of the coke. The 
fresh charge is made directly into the charging hole at top from 
the cars by means of portable chutes. The charge is then leveled in 
the oven by a long poker; the front door is closed by brick-work, and 
luted, excepting a small space at the top of the door-way, which is left 
open for the admission of air to consume the gases. At first a dense 
volume of smoke issues from the opening in the top of the oven, but in 
a short time the temperature of the oven has risen high enough to 
ignite the gaseous matter, which then bursts into flame and rises several 
feet above the top of the oven. The air admitted through the openings 
in the door-way should be only sufficient to sustain the combustion of 
