1 10 MINING nroUSTET. 



first desideratum, under ordinary circumstances, is to connect the new level 

 or station with the one above it by a winze, usually passing through the 

 ore-bearing ground, by which means a circulation of air is effected and the 

 necessary ventilation obtained. The stoping then commences, the work 

 progressing from the level of the new station upwards towards the station 

 next above; the ore, as fast as it is removed from place, being thrown down 

 to the track-level and transported from the stope to the shaft by means of the 

 drift-cars. 



The character of the quartz composing these ore-bodies is generally soft, 

 granular, and sometimes friable. It can generally be worked with a pick 

 without the aid of powder, though blasting is sometimes required. The ore 

 is very finely, almost imperceptibly, distributed throughout the mass and with 

 a general uniformity. Formerly the workable ores of the large producing 

 mines were divided into three classes. The first-class, forming now a very 

 small proportion of the whole and yielding, on an average, between $300 and 

 $400 per ton, usually occurring in bunches or pockets in the quartz, is, when 

 so found, removed to the surface in sacks. The second-class ores were such 

 as yielded from $75 to $150 per ton, while the third-class gave from $25 to $50 

 per ton. More recently, in some of the principal mines, these two classes, the 

 second and third, have been worked together as one without any attempt at 

 assortment. The average yield of these ores varies considerably in the differ- 

 ent mines and will be referred to further on. In stoping the ground, there- 

 fore, the entire mass of quartz is usually taken down and sent to mill without 

 any classification as to quality, except in the case of first-class ores, when such 

 occur. A rude assortment, however, for the purpose of distinguishing pay- 

 rock from that which is too poor to send to the miU, is sometimes rendered 

 necessary by the occurrence, within the mass of stoping ground, of belts of 

 low-grade rock or bunches of barren quartz, which would otherwise be sent 

 to the surface and worked at a useless cost. An experienced eye, aided, when 

 necessary, by assays, can distinguish by inspection the pay-rock from that 

 which is too poor to yield a profit. The latter then is assorted as well as pos- 

 sible and retained underground for the purpose of fiUing up the exhausted 

 chambers. This assortment, so far as observed, is not made by hand but by 

 inspection of the ground before breaking, the pay-rock being picked down 



