siderably; in small mines only a single
one may be used, but in the larger modern pits two-, three- or even
four-decked cages are used. The use of several decks is necessary in old
pits of small section, where only a single tram can be carried on each.
In the large shafts of the Northern and Wigan districts the cages are
made about 8 ft. long and 3-1/2 ft. broad, being sufficient to carry two
large trams on one deck. These are received upon a railway made of two
strips of angle iron of the proper gauge for the wheels, and are locked
fast by a latch falling over their ends. At Cadeby Main with four-decked
cages the capacity is eight 10-cwt. tubs or 4 tons of coal.

The guides or conductors in the pit may be constructed of wood, in which
case rectangular fir beams, about 3 by 4 in., are used, attached at
intervals of a few feet to buntons or cross-beams built into the lining
of the pit. Two guides are required for each cage; they may be placed
opposite to each other, either on the long or short sides--the latter
being preferable. The cage is guided by shoes of wrought iron, a few
inches long and bell-mouthed at the ends, attached to the horizontal
bars of the framing, which pass loosely over the guides on three sides,
but in most new pits rail guides of heavy section are used. They are
applied on one side of the cage only, forming a complete vertical
railway, carried by iron cross sleepers, with proper seats for the rails
instead of wooden buntons; the cage is guided by curved shoes of a
proper section to cover the heads of the rails. Rigid guides connected
with the walling of the pit are probably the best and safest, but they
have the disadvantage of being liable to distortion, in case of the pit
altering its form, owing to irregular movements of the ground, or other
causes. Wooden guides being of considerable size, block up a certain
portion of the area of the pit, and thus offer an impediment to the
ventilation, especially in upcast shafts, where the high temperature,
when furnace ventilation is used, is also against their use. In the
Lancashire and the Midland districts wire-rope guides have been
introduced to a very considerable extent, with a view of meeting the
above objections. These are simply wire-ropes, from 3/4 to 1-1/2 in. in
diameter, hanging from a cross-bar connected with the pit-head framing
at the surface, and attached to a similar bar at the bottom, which are
kept straight by a stretching weight of from