A 12 Iron, 
fuse coal is thrown in at the circular opening on the top, 
sufficient to fill the oven up to the springing of the arch ; 
it is then levelled with an iron rake, arid the door- way built 
up with loose bricks. The heat which the oven acquires 
in the former operation is always sufficient of itself to light 
up the new charge ; the combustion of which is accelerat- 
ed by the atmospheric ah that rushes in through the joints 
of the loose bricks in the doorway. In two or three hours 
the combustion gets to such a height, that they find it ne- 
cessary to check the influx of atmospheric air : the door- 
way is therefore now plastered up with a mixture of wet 
soil and sand, except the top row of bricks, which is left 
unplastered all night. Next morning (when the charge 
has been in 24 hours) this is completely closed also ; but 
the chimney remains open till the flame is gone, which is 
generally quite off in 12 hours more; a few loose stones 
are then laid on the top of the chimney, and closely cover- 
ed up with a thick bed of sand or earth. All connexion 
with the atmosphere is now cut off, and in this situation 
the whole remains for 12 hours, to complete the operation. 
The doorway is then opened, and the coaks are raked out 
into wheelbarrows, to be carted way. The whole takes 
up 48 hours ; and as soon as the coaks are removed, the 
ovens are again filled with coal for another burning. About 
2 tons of coals are put in for each charge. These coaks 
are ponderous, extremely hard, of a light grey colour, and 
shine with metallic lustre. They are used in those manu- 
factures that require an intense heat. 
When coak is required to be more of the nature of char- 
coal, the process is conducted in a different manner. The 
small coal is thrown into a large receptacle similar to a 
baker’s oven, previously brought to a red heat. Here 
the door is constantly open, and the heat of the oven is 
sufficient to dissipate all the bitumen of the coals, the 4is 
