ffect of bending
strains in the rope by change in direction, have channelled cast iron
rims with wrought iron arms, a form combining rigidity with strength, in
order to keep down their weight.

To prevent accidents from the breaking of the rope while the cage is
travelling in the shaft, or from over-winding when in consequence of the
engine not being stopped in time the cage may be drawn up to the
head-gear pulleys (both of which are unhappily not uncommon), various
forms of safety catches and disconnecting hooks have been adopted. The
former contrivances consist essentially of levers or cams with toothed
surfaces or gripping shoes mounted upon transverse axes attached to the
sides of the cage, whose function is to take hold of the guides and
support the cage in the event of its becoming detached from the rope.
The opposite axes are connected with springs which are kept in
compression by tension of the rope in drawing but come into action when
the pull is released, the side axes then biting into wooden guides or
gripping those of steel bars or ropes. The use of these contrivances is
more common in collieries on the continent of Europe, where in some
countries they are obligatory, than in England, where they are not
generally popular owing to their uncertainty in action and the constant
drag on the guides when the rope slacks.

For the prevention of accidents from over-winding, detaching hooks are
used. These consist essentially of links formed of a pair of parallel
plates joined by a central bolt forming a scissors joint which is
connected by chain links to the cage below and the winding-rope above.
The outer sides of the link are shaped with projecting lugs above. When
closed by the load the width is sufficient to allow it to enter a
funnel-shaped guide on a cross-bar of the frame some distance above the
bank level, but on reaching the narrower portion of the guide at the top
the plates are forced apart which releases the ropes and brings the lugs
into contact with the top of the cross-bar which secures the cage from
falling.

Three principal patterns, those of King, Ormerod and Walker, are in use,
and they are generally efficient supposing the speed of the cage at
arrival is not excessive. To guard against this it is now customary to
use some speed-checking appliance, independent of the engine-man, which
reduces or entirely cuts off the steam supply when the cage arrives at a
particular point near the surface, and