COAL MINES OF JACKSON COUNTY. 1023 
width left between them, which is cut through every 40 yards or less 
for air. The rooms are driven 70 to 80 yards, and extend both north 
and south, meeting in the middle. They are made 8 yards wide, a 
pillar of 3 to 4 yards being left between them for the support of the 
superincumbent strata. Break-throughs are made between rooms at 
intervals of 25 to 30 yards. 
In the Coalton district, instead of driving double entries, one 
wide entry is made, and the material which is shot out of the roof to 
make height for the hauling roads, is built up on one side of the track, 
leaving a hollow space next the pillar to serve as an air-course. By 
this plan a saving is had in entry driving, and the air is made to play 
along the entry face at all times. Asa temporary expedient this plan 
does very well, but after a few months the loose building of shale 
begins to settle and the air to leak. 
Where single entries are driven, doors are placed at the mouths 
of rooms and break-throughs made between runs as soon as they are 
turned, for the purpose of getting forward air. ‘These doors are never 
air-tight at best; they are frequently left open by the carelessness of 
the miners themselves, and bad air is found at the working faces of 
the mine. 
The system of working with double entries, if systematic per- 
fection in ventilation be desired, is greatly to be preferred over single 
entry work; but the latter method is cheaper than the former, and 
economy in mining has too often the first claim upon the managers of 
mines, as against the health and comfort of the miners. 
In the majority of the mines of Jackson county, the undermining 
or huling is made on the top of the coal. This part of the seam is 
tender and friable, and is more rapidly cut than the bottom part of the 
bed, which in many of the miners’ working places is a hard, unyield- 
ing bone coal. The undermining is made four to five feet deep, and 
powder does the rest; powder, in fact, is too often used to do the 
undermining also; though always unwisely. Three shots are ordinarily 
required to a room of 8 yards in width—one center and two rib shots. 
In the four-foot coal mines, mules enter the rooms and haul away 
the coal. Where the seam is less than four feet, pushers, consisting of 
active young men, are employed to push the loaded cars from the 
room faces to the hauling roads, on the entries. These hauling roads 
are made four-and-a-half to five feet in height above the rail, a foot or 
