TUE COAJMOX METHOD. 705 



the kiln. These are usually in two rows, somewhat below the 

 flame at the top of the kiln. At first, the smoke issuing from 

 these holes contains steam, but the nearer the combustion 

 approaches the holes, the clearer, more pungent and pyroligneous 

 it becomes ; when it finally turns blue, it denotes that the 

 charcoal is burning. Before the smoke turns blue, therefore, 

 the upper holes must be closed with paste and a flat shovel, and 

 a fresh row opened below the lower row. If burning proceeds too 

 rapidly on anv side of the kiln, all vent-holes must be stopped, 

 the covering thickened and water applied if necessary. 



By means of these simple arrangements, w-hich require the 

 burners' close attention, the wood in the kiln is gradually 

 carbonised. When the carbonisation is nearly over, the fire is 

 at the base of the kiln, ; holes are then opened there through 

 which at length flames protrude showing that the burning is 

 completed. The burners must now be on the watch to 

 extinguish the fire at the right moment, and prevent any 

 cracking or bursting of the covering by applying fresh paste or 

 watering the kiln. 



During the kindling process, the shaft of the flue, 

 especially in its upper part, burns completely and leaves a 

 hollow space in the kiln. HoUoavs may also form in other parts 

 of the kiln owing to a defective site, to bad piling, kindling or 

 control of the burning, or to the wood being too damp. If these 

 hollows were not filled, they would cause a draught and attract 

 the fire, the normal course of the burning would be hindered 

 and the yield of charcoal reduced. Owing to the continual 

 increase in size of these hollows, the covering might at length 

 fall in and the kiln burst into flames. All hollows must there- 

 fore be promptly filled with short pieces of wood or large pieces 

 of charcoal. 



The following method of filling hollows is adopted : — when- 

 ever the burners have noticed that owing to a marked collapse 

 of the covering a hollow has been formed, and have placed the 

 wood or charcoal required to fill it alongside the kiln, they 

 should test the extent of the hollow by tapping the covering 

 with a mallet. They then remove the covering over the hollow, 

 press down the contents with a piece of wood and till the hollow 

 rapidly covering it again with branches and paste, and beat 



VOL. V. z z 



