applies the brake if the load is
travelling too quickly. Maximum speed controllers in connexion with the
winding indicator, which do not allow the engine to exceed a fixed rate
of speed, are also used in some cases, with recording indicators.

Striking and screening.

When the cage arrives at the surface, or rather the platform forming the
working top above the mouth of the pit, it is received upon the keeps, a
pair of hinged gratings which are kept in an inclined position over the
pit-top by counter-balance weights, so that they are pushed aside to
allow the cage to pass upwards, but fall back and receive it when the
engine is reversed. The tubs are then removed or struck by the landers,
who pull them forward on to the platform, which is covered with cast
iron plates; at the same time empty ones are pushed in from the opposite
side. The cage is then lifted by the engine clear of the keeps, which
are opened by a lever worked by hand, and the empty tubs start on the
return trip. When the cage has several decks, it is necessary to repeat
this operation for each, unless there is a special provision made for
loading and discharging the tubs at different levels. An arrangement of
this kind for shifting the load from a large cage at one operation was
introduced by Fowler at Hucknall, in Leicestershire, where the trains
are received into a framework with a number of platforms corresponding
to those of the cage, carried on the head of a plunger movable by
hydraulic pressure in a vertical cylinder. The empty tubs are carried by
a corresponding arrangement on the opposite side. By this means the time
of stoppage is reduced to a minimum, 8 seconds for a three-decked cage
as against 28 seconds, as the operations of lowering the tubs to the
level of the pit-top, discharging, and replacing them are performed
during the time that the following load is being drawn up the pit.

In the United Kingdom the drawing of coal is generally confined to the
day shift of eight hours, with an output of from 100 to 150 tons per
hour, according to the depth, capacity of coal tubs, and facilities for
landing and changing tubs. With Fowler's hydraulic arrangement 2000 tons
are raised 600 yds. in eight hours. In the deeper German pits, where
great thicknesses of water-bearing strata have to be traversed, the
first establishment expenses are so great that in order to increase
output the shaft is sometimes provided with a complete double equipment
o