THE COMSTOCK MINES. 103 



Comstock resemble each other in general features, They are sunk vertically 

 and, as they pass through ground of rather unstable character, require to be 

 timbered from top to bottom. They are from 4:^ to 6 feet wide, and from 20 

 to 24 feet long, inside, between the timbers. They are usually divided into 

 four compartments, one for pumping and three for hoisting. Of the latter, 

 two compartments are usually devoted to the general work of hoisting from 

 the mine, while the remaining one is exclusively used in the further sinking 

 of the shaft. 



The present working shaft of the Savage mine, the description of which 

 may serve as an example of the others, is 24 feet long in the clear between 

 the end-timbers and 6 feet wide. It has three compartments for hoisting and 

 one for pumping. The latter is 6 feet square in the clear; the hoisting 

 compartments are 6 feet (the width of the shaft) by 5 feet, and the three 

 partitions between the compartments are formed of 12-inch timbers. 



Shaft Timbering. — The timbering consists of framed sets or cribs of 

 square timber, placed horizontally, 4 feet apart, and separated by uprights 

 or posts, introduced between them. Each horizontal set of timbers, therefore, 

 marks about 5 feet in depth. Cross-timbers, for the partitions between the 

 compartments, form a part of every set. The whole is covered on the outside 

 by a lagging of 3-inch plank placed vertically. This method of timbering is 

 illustrated by several drawings on Plates II and III. Fig. 1, Plate II, repre- 

 sents the plan of the shaft, or of one horizontal set of timbers ; S, 8, are 

 the longitudinal or sill-timbers ; T, T, the transverse end-timbers ; P, parti- 

 tion-timbers ; r, guide-rods, between which the cage moves ; g, gains, cut 

 in the sill-timbers, to receive the ends of the posts. The sheathing or 

 lagging is seen inclosing the whole frame. 



Fig. 2, on the same Plate, is a transverse section through the partition P 

 of Fig. 1, between the pumping compartment and the adjoining hoisting com- 

 partment, looking toward the latter. In this figure, G, G, are the posts ; S 

 the sill-timbers ; P, the partition-timbers, the ends of which are framed with 

 short tenons that are received in gains cut in the sill-timbers and the ends of 

 the posts ; r, guide-rod ; /, lagging or sheathing. Fig. 3 is an end view of the 

 frame, shown in Fig. 1. The single piece T forms the end, while the double 

 pieces, P, forming the partitions, are seen beyond. The other letters denote 

 the same parts as in Fig. 2. 



