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Coal to 40 and eyen 50 per cent., thus leaving little more 
than 3,000 tons of large Coal yielded per acre. 
You will easily understand what a fearful loss this must be 
in an extensive Colliery, where such Coal will only realise in 
the market from 2s. 6d. to 3s. 6d. per ton; consequently, 
where there is not a sufficient manufacturing demand at 
hand, and it will not readily make into coke, it is found 
better to save the carriage of it by leaving a portion in the 
goaf along with any other refuse obtained in getting the 
Coal. The refuse in many Collieries is very considerable, 
particularly where the seam of Coal is divided by partings of 
shale and earth. This is an item of very serious trouble and 
expense in many mines. It would be a great gain to the 
country if the Coal dust, which we see accumulated in heaps at 
all large collieries, could, either by improved mechanical 
arrangement, be consumed as Coal, or manufactured into 
artificial fuel. The former expedient has been attempted 
by Mr. Thomas Russell Crampton, at Woolwich, with his 
Coal Dust Furnace ; and the latter alternative by mixing 
dry pitch with the same, under a process invented by 
M. Chagot, the engineer to some Coal Mines in Saone et 
Loire, France, both experiments resulting in a fair measure 
of success. 
Holing in the Coal is, at all times, productive of much 
tcaste ; consequently, where the ground or base of the Coal is 
of a soft nature (more usually so than otherwise) the holing 
should be made in the seam of under clay usually existing 
below the Coal. 
I now come to the brief consideration of "Longwall" 
workings, as illustrated in my plan marked No. 2., the 
distinguishing feature of which is the extraction of the whole 
of the Coal (after leaving sufficient for the support of the 
shafts) in the first process of working, by means of long con- 
tinuous faces* The preliminary operations of this system 
