SACK 



731 



a small hole in centre of hook for a J-inch pin to be rivetted in for holding the 

 plates secure when in work care must be taken not to work without it ; when drawn 

 up to c c it is sheared in four parts ; the hole B is to put a drift in for holding the 

 plates square, so as to punch the sheared pin out. 



The detaching hook is simple in construction, and it appears to be effectual and 

 certain in action, and is said not to be very liable to get out of order. 



SAFETY CAGE. In all our collieries the men descend to their labour and are 

 raised from the depth of the mines by winding machinery. This may be described 

 in general terms as a stage travelling in-guides fixed to the sides of the shafts. The 

 rapidity with which these stages are moved up or down is very great, and conse- 

 quently, if anything occurs to engage the attention of the man in charge of the 

 winding-engine, the stage with its living load is either landed with injurious violence 

 at the bottom of the pit, or it is carried over the pulley, and thus the lives of the 

 men are sacrificed. The engraving, fig. 1739, shows an ingenious contrivance for 

 obviating the blow which arises from reaching the bottom at too great a speed, e e, are 



1739 



platforms placed on india-rubber springs b b (see CAOUTCHOUC), on the landing at 

 the bottom of the pit ; d, is one of the cages which has descended, the other being 

 supposed to be at the surface. The elasticity of these springs certainly serves to 

 protect the men from the violence of the concussion in the event of the rope breaking, 

 or if from any other cause they suddenly reach the bottom. 



Many safety cages, have been invented, in which the principles are to allow them 

 to travel freely on their guides, so long as the rope by which they are suspended re- 

 mains entire ; but, in the event of its breaking, arms, levers, or catches, are released ; 

 these seize the guide-rods, and thus suddenly stop the cage. Experience has not 

 satisfactorily confirmed the value of these arrangements. 



The remarks made by the reporter on the Safety Cages exhibited in the Inter- 

 national Exhibition of 1862 are well worthy of consideration : 



' The jury gave careful attention to all the varieties of this apparatus, and were 

 strongly impressed with the merits of several of them, and with the desirableness of 

 enlisting in this cause the interest of the intelligent mechanician. But they share 

 in the repugnance of colliery viewers to trust to the action of a spring, on which 

 most of them depend; and which, of whatever substance it is made, is sure, by 

 degrees, to lose its elasticity, and is thus liable, unless frequently looked after, to fail 



