126 GEOLOGICAL SURVEY OF ALABAMA. 
to himself, with an electric light at each crane during work- 
ing hours. The ends of the room tracks must be curved up 
so as to prevent the mine car from ever running into the 
slope. The first diagram opposite shows a section along 
the slope, and across the room entrances and the entrance 
to two rooms. 
In this method the amount of work necessary to fit up 
the post crane and make the siding, is not half that required 
to open a room and put ina switch in the ordinary level 
gangway. To fit up the post crane, all that is required is 
to dig a hole in the roof sufficiently deep to hold the head 
of the post and prevent its slipping, then dig another hole: 
exactly under that one (by a plumb line), in the bottom 
slate, put in place the post which is of ironand in two parts. 
fitting one into the other by a screw, and turn it after the 
manner of a jackscrew, until it presses sufficiently against 
roof and floor to prevent its moving. The remainder of the 
work consists in digging off the corner of the slope pillar 
sufficiently to make room for the empty car to stay out of 
the way of both slope track and room track. 
The scaffold in the siding is not absolutely necessary, but 
a light one there would enable the miner to have an extra 
empty car. The end of the mine car body must have two 
hitching or hooking places, one at its top edge of the car for 
the miners use, the other about the middle of the end of the 
car for the top or bankman to hook to for dumping the coal 
on the screen. This method has the great advantage of 
allowing the mine car wheels to be fastened to the axle in 
both slope tram and mine cars. There are no curves to go 
around, therefore no slip of wheels; mine cars with wheels. 
fastened to the axle, the axle itself rotating, will last proba- 
bly twice as long as those that are loose and have the axle 
bolted to the bottom of the cars; they also run much lighter 
and keep the proper gauge much longer. The second dia-. 
gram opposite, giving a section along the room roads and 
across the hoisting slope, shows the arrangement of the 
screw threads and crank for raising the mine car body from 
the tram truck or from slope tram. 
In this method the Engineman must havein front of him 
(with the end towards him, and its lower edge about eight 
