236 
This is under the result actually realised, as the writer, in 
these calculations, has assumed the same sale price for Coal 
got by both methods, whereas. Coal got in large cubical 
blocks (as obtained under this system of Longwall on end), is 
worth at least 6cl. per ton more than the same Coal got 
boardway. 
In presenting these returns to you, I may possibly be 
charged with having selected an exceptionally favourable Coal 
seam ; such, however, is not the case, as the *'Middleton Main" 
is certainly not the most economical Coal in the series, so far as 
concerns its economical adaptation to Longwall workings. I 
do not say these gratifying results can be obtained in every 
seam of Coal, but I do believe, after a very careful investiga- 
tion of the subject, that there are few seams where such a 
system could not be adopted with advantage; and the 
analysis I have given from results actually obtained in 
the same bed of Coal, show what an important part the 
method employed bears in the economical working of our 
Coal fields. 
The ventilation, under this system, is obtained as follows, 
and is characterised by its remarkable simplicity: — The work- 
ings of the pit are divided into districts, to each of w^hich is 
supplied a separate current of fresh air, which is delivered at 
the face of the Coal without that waste in its journey, which 
is involved in any system of pillar workings. The air, after 
travelling over the limited district assigned to it, passes into 
a return air course made through the goaf ; into these roads 
there are cross roads from the intake air courses, to furnish 
a limited quantity of fresh air, for rendering any obnoxious 
gases harmless in their passage to the upcast shaft, thus puri- 
fying the goaf without adulterating the air passing along the 
face of the Coal. 
All the main roads used in working, and for the passage of 
air, should be constructed as large as possible, so as to obtain 
