402 
GARFORTH : FIRE-DAMP DETECTOR. 
sectional area. This raises the second difficulty of dealing" with the 
effects of the superincumbent weight. 
Considering the difficulty and heavy cost of increasing the 
velocity, it becomes a question whether it will not in the future be 
more advantageous to reduce the temperature by artificial means. 
As regards the effects of the superincumbent strata at great 
depths, it seems to be a difficulty quite as serious as increase of 
temperature. Pillars of coal, which formerly resisted the effects of 
the overlying strata, are now much crushed even if a larger propor- 
tion of pillar be left. Of course no system of working can diminish 
the pressure, but on the contrary, must increase it. The faults 
of a wrong system of working, which were not apparent at shallow 
depths, are now seen by an increased proportion of small coal, 
which in most instances makes the difference between profit and loss. 
There is also the difficulty (a most serious one) of the liability 
of sudden outbursts, which has been the cause of several dreadful 
colliery explosions. 
From the foregoing it would seem that coal has been placed 
within our reach, but apparently too deep for work ; and when the 
hands are stretched forth to obtain it, a sacrifice of life takes place. 
But when we remember, and from statistics published by the Royal 
Commission, that only 60 per cent, of the produce of the seam was 
formerly obtained in some districts, it would appear as if coal had 
been Divinely stored at a great depth to prevent it being wasted, 
both in the method of getting and in the consumption. At the 
present time, as much as 95 per cent, (in some cases more) of the 
seam is obtained, and 2ift)S. of coal per hour per horse power, is now 
doing the same amount of work that some years ago required 4 to 5ibs. 
The writer believes it is possible to overcome many of the 
difficulties that have been referred to, by a better and more system- 
atic method of working. When we take into account that most 
mines rest upon an under clay, it will be understood that the same 
pressure which is crushing the coal is also affecting the dirt. 
If that effect is only properly studied, it is possible it may not only 
be the means of saving the coal, but by being crushed into suitable 
pieces for packing, it will enable the goaf to be filled, and thus 
