underground motors
driven by steam, compressed air or electricity.

Where the water does not accumulate very rapidly it is a common practice
to allow it to collect in a pit or sump below the working bottom of the
shaft, and to draw it off in a water tub or "hoppet" by the main engine,
when the latter is not employed in raising coal.

Laying out workings.

The laying out of a colliery, after the coal has been won, by sinkings
or levels, may be accomplished in various ways, according to the nature
of the coal, its thickness and dip, and the extent of ground to be
worked. In the South Staffordshire and other Midland coalfields, where
only shallow pits are required, and the coals are thick, a pair of pits
may be sunk for a very few acres, while in the North of England, on the
other hand, where sinking is expensive, an area of some thousands of
acres may be commanded from the same number of pits. In the latter case,
which represents the most approved practice, the sinking is usually
placed about the centre of the ground, so that the workings may radiate
in every direction from the pit bottom, with the view of employing the
greatest number of hands to advantage. Where a large area cannot be
commanded, it is best to sink to the lowest point of the field for the
convenience of drawing the coal and water which become level-free in
regard to the pit. Where properties are much divided, it is always
necessary to maintain a thick barrier of unwrought coal between the
boundary of the mine and the neighbouring workings, especially if the
latter are to the dip. If a prominent line of fault crosses the area it
may usually be a convenient division of the fields into sections or
districts. The first process in laying out the workings consists in
driving a gallery on the level along the course of the coal seam, which
is known as a "dip head level," and a lower parallel one, in which the
water collects, known as a "lodgment level." Galleries driven at right
angles to these are known as a "dip" or "rise headings," according to
their position above or below the pit bottom. In Staffordshire the main
levels are also known as "gate roads." To secure the perpendicularity
of the shaft, it is necessary to leave a large mass or pillar of the
seam untouched around the pit bottom. This pillar is known in Scotland
as the "pit bottom stoop." The junction of the levels with the pit is
known as the "pit eye"; it is usually of an enlarged section, an