6 Field Miisettm of Natural History 



In PROSPECTS, that is, preliminary workings 

 to determine the value and nature of an ore deposit, 

 the shafts usually have but one compartment and in 

 some districts of small mines one compartment shafts 

 are common. On the other hand larger mines usually 

 have more than two compartments. Three and four 

 compartment shafts are usual. 



The shaft is strengthened by a skeleton lining of 

 heavy timber. Horizontal rectangular frames spaced 

 at frequent intervals are firmly held in place against 

 the rock by wooden wedges. These frames, called 

 SETS, are connected as a continuous framework by 

 upright posts at the four corners. Other uprights 

 mark the division between the compartments. Cross 

 timbers in each set complete the timbering and sepa- 

 rate the compartments. 



Near the surface, where the shaft passes through 

 soil and broken rock, further protection is necessary. 

 This is provided by LAGGING, which is a plank lining 

 to the shaft. 



In the hoisting compartment is the CAGE. This 

 is an elevator much like the elevator of an office build- 

 ing. On this cage, the cars of ore are raised and 

 access to the workings is provided for supplies and 

 men. Over the top of the shaft is the HEAD-FRAME. 

 This carries at its summit a pulley over which the 

 cable from the cage passes to the HOISTING EN- 

 GINE housed in a building at the rear. At the bottom 

 of the model the shaft is continued to form a kind of 

 cistern called the SUMP in which the mine waters 

 collect. On the lower level of the mine to the left of 

 the shaft is the PUMP driven by an electric motor. 

 This takes the water from the sump and delivers it to 

 the COLUMN, a large pipe in the ladder-way, through 

 which it passes to the surface. 



[6] 



