MINING. 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 surface 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 many facilities for working 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 
info 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 diggings are in a flat. Bench dig- 
gings are in a “bench” or narrow table on the side of a hill 
love a river. Benches of this kind are not uncommon in 
Cahfornia, 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 ‘vater from the bed by flumes or ditches. Au- 
cient river-bed claims are those of which the gold was deposited 
by streams in places where no streams now exist. Gulch claims 
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