THE PACIFIC SLOPE. 245 



gold has been derived principally from the quartz veins of the 

 slates, which are later described, and has been mechanically con- 

 centrated in the streams. Before coming to its final rest it may 

 have lodged in the high or deep gravels, of which mention will 

 next be made. 



It is accompanied by magnetite as a general thing, by zircon, 

 garnet, and rarely by other heavy metals, such as platinum and 

 iridosmine. The greatest amount is usually near the bed rock, 

 and when this is at all porous the gold may work into it to a small 

 distance from the top. The gold is usually in flattened pellets of 

 all sizes, from the finest dust to nuggets of considerable weight. 

 They show evidence of being water worn. The interesting phe- 

 nomena connected with the possible circulation of the precious 

 metal in solution through the gravels are discussed under the deep 

 gravels. Important deposits of the same general character as these 

 have also been dug over near Santa Fe, N. M. ; in California 

 Gulch, near Leadville, Colo.; at Fairplay, Colo.; in San Miguel 

 County, Colorado ; in the Sweetwater district, Wyoming ; near 

 Butte, Mont. ; in Last Chance and Prickly Pear gulches, near 

 Helena, Mont.; in the Black Hills; in southern Idaho, especially 

 along the Snake River ; and at various points in Washington and 

 Oregon. Placers of this type have also been found on the slopes 

 of the Green Mountains and in the Southern States, but they never 

 have proved of serious importance. 



2.12.09. (2) High or Deep Gravels. With the exhaustion of 

 the river gravels the gold seekers of California were driven to 

 prospect on the higher slopes, where auriferous gravels much less 

 accessible had been long noted. Increasing observation and de- 

 velopment have shown that these are the relics of a former and 

 very extensive drainage system, which was more or less parallel 

 with the present streams, but of greater volume. The beds lie in 

 deep gulches in the slates, and are capped in most cases by basal- 

 tic lava flows or by consolidated volcanic tuffs, called cement. 

 They extend some 250 miles along the Sierras and up to 5000 feet 

 above the sea. They have at times great thickness, reaching 600 

 feet at Columbia Hill, but drop elsewhere to 1 or 2 feet. They vary 

 from a maximum width in workable material of 1000 feet to a mini- 

 mum of 150. The inclosing slates on the sides of the old river 

 valley are called " the rims," and on them are sometimes found 

 other gravels. In some districts channels, belonging to two or 

 three periods of flow, have been traced. They tend to follow the 



