COKE 



but a complete combustion of the volatile principles of the coal. The mass of coals 

 is first kindled at the surface, where it is supplied -with abundance of atmospheric 

 oxygon ; because the doors of the ovens in front, and the throat-vents behind, are 

 then left open. The consequence is, that no smoke is discharged from the top of the 

 chimney, at this, the most sooty period of the process, than is produced by an ordinary 

 kitchen fire. In these circumstances, the coal gas, or other gas, supposed to be gone- 

 rated in the slightly heated mass beneath, cannot escape combustion in passing up 

 through the bright open flame of the oven. As the coking of the coal advances more 

 slowly and regularly from the top of the heap to the bottom, only one layer is affected 

 at a time, and in succession downwards, while the surface is always covered with a 

 stratum of red-hot cinders, ready to consume every particle of carburetted or sul- 

 phuretted hydrogen gases which may escape from below. The greatest mass, when 

 calcined in this downward order, cannot emit into the atmosphere any more of the 

 above-mentioned gases than the smallest heap. 



The coke being perfectly freed from all fuliginous and volatile matters by a cal- 

 cination of upwards of 40 hours, is cooled down to a moderate ignition by sliding-in 

 the dampers, and sliding-up the doors, which had been partially closed during the 

 latter part of the process. It is now observed to form prismatic concretions, somewhat 

 like a columnar mass of basalt. These are loosened by iron bars, lifted out upon 

 shovels furnished with long iron shanks, which are poised upon swing chains with 



497 



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498 



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499 



hooked ends, and the lumps are thrown upon the pavement, to be extinguished by 

 sprinkling water upon them from the rose of a watering can ; or, they might be 

 transferred into a large chest of sheet-iron set on wheels, and then covered up. Good 

 coals, thus treated, yield 80 per cent, of an excellent compact glistening coke, weighing 

 about 14 cwts. per chaldron. 



The loss of weight in coking in the ordinary ovens is usually reckoned at 25 per 

 cent. ; and coal, which thus loses one-fourth in weight, gains one-fourth in bulk. 



Labourers who have been long employed at rightly-constructed coke ovens seelB. to 

 enjoy remarkably good health. 



Mr. Ebenezer Eogers, of Abercarn, in Monmouthshire, introduced a method of 

 coking, which he thus described : 



' A short time ago a plan was mentioned to the writer as having been used in 

 Westphalia, by which wood was charred in small kilns : as the form of kiln described 

 was quite new to him, it led him to some reflection as to the principles on which it 

 acted, which were found to be so simple and effective, that he determined to apply 



