GEOLOGY. 53 



and from six to eight times heavier than the clay and stones 

 with which it is found, has sunk to the bottom of the dikivium. 

 Tlie best diggings are therefore near the "bed-rock." The 

 dirt in which the gold is found is usually a stiff clay, with 

 gravel and large stones intermixed. The common phrase 

 " golden sands" may mislead. Pure, fine sand rarely has any 

 gold in it ; and the richest deposits of the precious metal are 

 in a clay so tough as to give the miner much trouble to dis- 

 solve it, with stones in it weighing from a pound to several 

 hundred weight. The character of the pay-dirt varies greatly. 

 A hill of diluvium may be three hundred feet deep, with a 

 dozen strata of different material, and all of them auriferous in 

 different degrees. In some places the pay-dirt is full of boul- 

 ders, weighing several hundred pounds or more ; in other 

 places the stones are all about as large as a man's head ; in 

 others, as large as a hen's egg. In one stratum the dirt is 

 red, in another blue, in another brown. In some places the 

 dirt was deposited in basins of rock, four or five miles across, 

 and from ten to fifty feet deeper at the centre than at the rim. 



The placer-diggings are all found in a very rough, mountain- 

 ous country. The gold has not been carried far ; its weight 

 has anchored it near its mother-vein. There may be much 

 gold in the Sacramento valley ; but if so, it is deposited be- 

 neath one thousand feet of diluvium, and nine hundred feet 

 below the level of the sea, where it will never be disturbed. 



The diluvial placers are in what are called hill and flat dig- 

 gings; the alluvial, made by streams running through the 

 diluvium, are in rivei'-beds, bars, ravines, and gullies. The 

 alluvial placers, as a general rule, are richer than the diluvial. 

 The streams have carried away much of the dirt, and left 

 nearly all the metal. Most of the gold of the rivers comes 

 from gullies. There is a gully on a mountain : it is dry, ex- 

 cept during heavy rains ; it has steep sides. The rain comes ; 

 the water pours down its sides, fiercely sweeping clay, gravel, 

 and gold along. Tlie bed of the ravine is not so steep as the 

 Bides ; most of the gold stops there ; the dirt is carried away 



