COKE MANUFACTURE. 565 
state of the weather, etc. ‘The channels are kept open by a rod, and in 
ordinary circumstances the operation will be completed in about 8 days, 
when the openings are all closed and luted, and in 2 or 3 days the end 
wall is removed, the coke extinguished and discharged. ‘The yield of 
coke in the furnaces in Upper Silesia was from 50 to 55 per cent. 
The principal advantage claimed by the use of this kiln is that it 
produces a dense and hard coke, bearing transport well, beside which 
the product is regular and the labor not difficult. It is specially fitted 
for the carbonization of fine coal. The furnace is not expensive to con- 
struct, as near Cologne a furnace to hold 34 tons cost about 3,130 
francs ($626). . 
The charge of coal used in the furnaces erected in the Ruhr and 
Soar basins was from 7% to 54 tons, depending upon their size, and the 
time of coking about 6% days, the yield being from 60 to 70 per cent. of 
coke. ‘Though these furnaces were largely -used in Germany in 1850, 
they are said now to be no longer employed. 
In some of those built in the French coal basins, the holes in the 
side-walls were made at a level with the bottom of the furnace, and 
their width inside was 6% feet, their length 197? feet, and their height 
31 feet, leaving a capacity of 18 to 20 tons of coal. The yield of these 
furnaces with the French coals was from 60 to 65 per cent. 
In 1857 the same process was patented in England by Mr. E. 
Rogers, he believing it, however, to be a new invention, and kilns were 
- erected at various establishments in Wales, where the process had an 
extended trial. Mr. Rogers considered the best dimensions to be 90 
feet long, 14 wide, and 73% feet high inside, holding about 150 tons of 
coal. In Wales they were said to produce 75 per cent. of coke, with a 
saving in working expenses of 50 per cent., besides that the’eoke was 
considered more dense and uniform, but all the furnaces erected there 
on this plan are believed to be now abandoned. 
Coking in ovens. The previously described methods are well 
adapted for coking bituminous coals, possessing good coking proper- 
ties, but as generally practiced, it requires the larger portion of the 
coal to be in lumps, or at least not fine. While coal coked in heaps 
or piles will yield 60 to 65 per cent., the same coal coked in good ovens 
will yield from 75 to 80 per cent. of coke, which is at the same time of 
better quality, harder and more uniform. The former method, how- 
ever, has the advantage of requiring no outlay for expensive structures. 
