278 RESOUKCES OF CALIFORNIA. 



tunnels. After the excavation has extended twenty or tliirty 

 feet below the surface, it is usual to dig a perpendicular shaft, 

 so as to strike the vein sixty or seventy feet below the surface, 

 and from this point the miner or " drifter" works upward, and 

 as he loosens the rock it falls to the bottom of the shaft, M'here 

 it is put in the bucket to be hoisted to the surface. Our quartz 

 mines are generally in dry hills, so that they are not troubled 

 much by water ; but there are a few shafts where steam-pumps 

 are constantly at work to carry off the water. 



Occasionally the miners find small quantities of auriferous 

 quartz which are so easily broken up, and the pieces of gold in 

 which are so coarse, that after the rock has been pounded a 

 little in a mortar, the metal can easily be picked out with the 

 fingers. 



§ 208. Arastra. — Quartz is pulverized either in an arastra, 

 or Chilean mill, or by stamps. 



The arastra is the simplest instrument for grinding aurifer- 

 ous quartz. It is a circular bed of stone, from eight to twenty 

 feet in diameter, on which the quartz is ground by a large 

 stone dragged round and round by horse or mule power. 

 There are two kinds of arastras, the rude or improved. The 

 rude arastra is made with a pavement of unhewn flat stones, 

 which are usually laid down in clay. The pavement of the 

 improved arastra is made of hewn stone, cut very accurately 

 and laid down in cement. In the centre of the bed of the 

 arastra is an upright post which turns on a pivot, and running 

 through the post is a horizontal bar, projecting on each side to 

 the outer edge of the pavement. On each arm of this bar is 

 attached by a chain a large flat stone or muller, weighing from 

 three hundred to five hundred pounds. It is so hiing that the 

 forward end is about an inch above the bed, and the hind end 

 drags on the bed. A mule hitched to one arm will drag two 

 such mullers. In some arastras there are four mullers and two 

 mules. Outside of the pavement is a wall of stone a foot high 

 to keep the quartz within reach of the mullers. About four 

 hundred pounds of quartz, previously broken into pieces about 



