THE COMSTOCK MINES. 113 



and the perspective view on Plate V, illustrate this method of timbering in 

 stopes. Fig. 2, Plate IV, presents an elevation and a plan of a single set, 

 showing the details of the framing ; while the view on Plate V shows the 

 general arrangement of a series of sets when put together in a stope of the 

 mine. 



The timbers are usually of 12-inch stuff, square-hewn or sawed. They 

 are framed with much care so that the various parts fit snugly together. Each 

 piece, excepting, occasionally, the ground-sill or foundation-timber of a new 

 series of floors, as explained further on, is cut and framed separately. This is 

 sometimes done by hand, sometimes by machinery. The latter is the case at 

 the Savage, where a system of circular saws and planers, adjustable by set- 

 screws, is so arranged that the piece of timber, held firmly by appliances 

 which permit of its being easily revolved or moved to and fro, can be brought 

 against them, the saws cutting the tenons of any desired dimensions and the 

 planers cutting the shoulders, either square or beveled. 



In the Savage mine the posts of the sets, above described, are 7 feet 2 

 inches high, including the tenons. These latter, 8 inches square or 8 by 10, 

 are 9 inches long on the upper end of post, and 2 inches long on the lower 

 end ; and as the caps and sills have ^-inch shoulders cut for the admission of 

 the ends of the posts, there remain 6 feet 3 inches in the clear between sills 

 and caps of each set. The sills and caps, 3 feet 9 inches in the clear, also 

 have short tenons on each end and shoulders cut to receive the ends of the 

 posts and horizontal cross-pieces. 



In some cases this method of framing is varied to suit the varying condi- 

 tions of the ground, so that, if the pressure is chiefly a vertical one, the tenons 

 of the posts are cut as just described, bringing the ends of each post in direct 

 contact with its neighboring post, above and below, without introducing 

 between them the tenons of the horizontal timbers, which would offer less 

 resistance to a pressure at right angles to the fibre of the wood ; while if the 

 pressure be lateral instead of vertical the tenons of the posts are made short 

 and those of the horizontal timbers long, so that the latter may press directly 

 against each other without the intervention of the post-tenons. 



The stoping is, as already observed, all carried on overhand ; that is, a 



station, or level, is opened under the body of ore to be worked out and the 

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