MIXING. 241 



§ 178. Placer Mines. — Placer mines are divided into many 

 classifications. The first and most important is into deep and 

 shallow. In the former the pay-dirt is found deep, twenty 

 feet or more beneath the surface ; in the latter, near the sur- 

 face. The shallow or surfiice diggings are chiefly found in the 

 beds of ravines and gullies, in the bars of rivers, and in shal- 

 low flats ; the deep diggings are in hills and deep flats. The 

 pay-dirt is usually covered by layers of barren dirt, which is 

 sometimes washed, and sometimes left undisturbed, while the 

 pay-dirt is taken out from beneath it through tunnels or shafts. 

 So far as our present information goes, we have reason to be- 

 lieve that no gold country ever possessed so large an extent 

 of paying placer mines, with the pay-dirt so near the surface, 

 and with so manv fiicilities for workino- them as California. 

 In Australia the diggings are very deep and spotted, that is, 

 the gold is unevenly distributed, and the supply of water for 

 mining is scanty. In Siberia the winter is terribly cold during 

 six months of the year. In Brazil the diggings were not so 

 extensive nor so rich as in this state. Here we have numerous 

 large streams coming down through the mining districts, very 

 large bodies of pay-dirt, and a mild climate. 



After dividing placers into deep and shallow, the next clas- 

 sification will be according to their topographical position, as 

 into hill, flat, bench, bar, river-bed, ancient river-bed, and 

 gulch mines. Hill diggings are those where the pay-dirt is 

 in or under a hill. Flat disfcrino^s are in a flat. Bench dig;- 

 gings are in a " bench" or narrow table on the side of a hill 

 above a river. Benches of this kind are not uncommon in 

 California, and they often indicate the place where the stream 

 ran in some very remote age. Bars are low collections of 

 sand and gravel at the side of a river and above its surface at 

 low water. River-bed claims are those beneath the surface of 

 the river at low water, and access is obtained to them only by 

 removing the water from the bed by flumes or ditches. An- 

 cient river-bed claims are those of which the gold was deposited 

 by streams in places where no streams now exist. Gulch claims 

 11 



