232 
discipline inaugurated at the beginning, should be carefully 
carried out afterwards. 
The plan that I have made of piUar workings is, I think, 
one of the most economical that such a system will admit of, 
the ventilation having the advantage of supplying each dis- 
trict or sets of banks with its own separate portion of air, 
instead of the objectionable plan of carrying the air round 
the mine in a single current. On my plan the direction of 
the ventilation is shown by the arrows, and I have also marked 
the necessary air crossings and stoppings, etc. You will notice 
that the air is passed up the pillar board, on one side of the 
bank, along the crossgate, and into the return air road. I 
should first have mentioned that the preliminary operations of 
the mine consist of roads or endings being driven in pairs, 
following the cleavage of the Coal, at distances varying from 
twelve to twenty chains, according as the nature of the roof will 
admit of, and between these endings the Coal is got in banks 
of difierent widths, varying according to circumstances, from 
forty to sixty yards. Every set of banks consisting of some 
four or five boards, each about ten yards wide, out of which 
the Coal is brought, and conveyed along the main board into 
the ending leading to the pit bottom. A pillar of Coal is 
left between these banks, of about forty yards in width, which 
is brought back when the banks are finished. 
The area of Coal occupied in this way, in the form of 
pillars, is not less than 50 per cent, of the entire area of the 
Coal field ; and the production, instead of being about 6,000 
tons per acre in the seam now referred to, four feet thick, 
would realise only about 3,000 tons of Coal until such time 
as the pillars are removed; then again, this system pro- 
duces a large proportion of slack or small Coal, by reason 
of the holing required, and it being got facing the cleavage 
of the Coal. This, with the increase of slack produced in 
working the pillars, will often raise the percentage of small 
