562 GEOLOGY OF OJIIO. 
Maryland, the facts concerning the working of which have been kindly 
furnished by my friend, Mr. EK. F. Wendt, E.M., the Superintendent. 
The coal used is the semi-bituminous coal of the Cumberland coal basin, 
containing about 75 per cent. of fixed carbon. The piles are rectangular in 
plan, 42 by 12 ft., and conical in cross-section formed like the ridge of a 
roof, 5 feet in height. A flue is first built with the large pieces of coal, 
“lumps” or “tops,” on the base of the proposed pile along the axes of 
its greater dimension, and smaller pieces, about the size of a man’s head, 
are carefully laid against them over the whole area of the pit. This is 
called the “bottom,” and requires three layers to complete it. The pile 
is made upon this bottom by shoveling the coal upon it with pronged 
shovels, the prongs of which are 1? inches apart, and the whole is then 
finished by a covering of the fine coal, which is well moistened and 
beaten down, excepting a small space around the base, which is left un- 
covered. A pile of this shape and dimensions will contain 40 tons of 
coal. Fire is given to the pit at both ends of the central flue, and 
owing to the circulation through the flue and between the larger lumps 
of coal forming the bottom, the entire base is soon a glowing mass. The 
fire rises thence toward the top, and is followed by covering the lower 
portion of the pile with coke dust and ashes. In ordinary weather 
about 9 inches are left between the fire and the edge of the covering, 
but in wet weather this space is increased, and a greater draught is 
therefore given. When the fire has been driven to the top, which 
requires 8 or 9 days, and the pit is covered, it is left one or two days to 
cool. Holes are then punctured in the pile by a crow-bar, and water is 
run into the interior at a number of places in order to hasten its cooling 
and permit the removal of the cover, and breaking up of the pit. If, 
however, the pit is allowed to cool by itself or is smothered, it will 
require 5 days before the coke can be removed. As the coke is all 
removed by pronged shovels, a considerable quantity of fine coke or 
breeze is left in the yard, which is used for covering subsequent pits. 
The character and yield of coke will vary with the rapidity of the 
operation and the care with which it is done, but to obtain the best 
results, fully 2 weeks are required. The yield of the Cumberland coal 
in these pits is 485 per cent., or a 40-ton pit of coal will yield about 20 
tons of coke. | 
For the production of 50 tons of coke per day there will be re- 
