Polytechnic Association. 603 



be raised at a time. By this means each, hoist brings up 2,800 pounds 

 of ore instead of 1,400 pounds, and the expense of this part of the 

 work is diminished in a proportionate degree. Each cage is of 

 wrought iron, of skeleton form, to secure lightness, and is attached to 

 the end of a flat steel-wire rope, four inches wide and three-eighths 

 of an inch thick. These ropes have each a breaking strength of fifty 

 tons. They run upon sheaves nine feet in diameter, arranged imme- 

 diately over the shaft, and with their bearings in the timbers of the 

 roof, which is trussed to sustain the weight brought upon it in the 

 hoisting operations. From its sheave the rope of each apparatus 

 extends to a winding reel, to which its opposite end is attached, so 

 that the reel, when turning in one direction, will wind the rope to 

 elevate the cage, and, when rotated the opposite way, will release the 

 rope to permit the cage to descend. The circular rims of the reels 

 are fourteen feet in diameter, with radially projecting arms to prevent 

 lateral displacement. The axle shaft of the reels connects by large 

 spur wheels with a driving shaft, itself driven by the hoisting 

 engines — two connected horizontal ones, with ordinary slide valves 

 and link motion for reversing. These are employed for lifting ; but 

 in the descent of the cage, the engine power is disconnected from the 

 driving shaft by the movement of a clutch — the speed of the cage in 

 going down being regulated by a brake applied to the driving shaft 

 and under the control of an attendant. The hoisting of the ore is, 

 therefore, superintended by the engineer and the descent of the cages 

 by a brakeman. The driving shaft has connected with it a system 

 of gearing that gives axial motion to a vertical rod, that, in its turn, 

 actuates an index finger placed in suitable relation with a dial. The 

 parts are so adjusted that the index shows the exact position of the 

 cage at any depth in the shaft, so that the engineer or his assistant 

 may know at a glance the precise whereabouts of the cage, although 

 it be out of sight and hundreds of feet below. The derrick is also 

 furnished with an alarm, which rings when the cage rises to within 

 100 feet of the surface. The shaft has a signal rope extend- 

 ing from top to bottom, by which a passenger on the cages can signal 

 the engineer to stop at any desired point. It will be seen that the 

 shaft being made to secure access to the ore, and the hoisting appa- 

 ratus to bring it out of the mine, it remains to come within imme- 

 diate reach of the material, and to break it from its place. This is 

 done by running horizontal galleries, tunnels or drifts radially, in 

 different directions from the shaft. Each system of drifts is called 

 a level, and the levels are 100 feet, more or less, apart, one 



