Papers from the Notes of an Engineer (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1889 edition. Excerpt: ...in which the transported placer-forming substances are sifted, spread, arrested from farther travel, condensed and built up in layers, accompanied with a partial bed-rock concentration of the heavier ingredients, and finally carved out into the playas as seen to-day. These benches or terraces of auriferous gravel--the placers proper--are from five to fifteen feet high, and run with the river for distances of from 200 to 2,000 feet, with width ranging from 100 to 700 feet, extending back toward the slopes Play a. Gravel Ideal Section of the Timiani Placets. Scattered along the banks irregularly and in groves are pine-apple, rice and coffee plants, orange, lemon, coca, cascarilla, rubber, cotton, cane, banana, and divers nut-trees. The predominating countryrock throughout the river is hard, non-fossiliferous, slightly ferruginous blue clay-slate, the same as observed at great altitudes on the northeast slope of the Cordillera in violently upheaved beds hundreds of feet thick. Lower down in the foot-hills, they are overlaid with friable red shales or weathered mica-schist, on which are superimposed conglomerates, red clay, and thick deposits of TopQjtvr/i brown soil of reddish hue. And although this order of superincumbent strata, which, collectively taken, is the gold-containing formation, is only noticeable in places, along the river, the slates appear often reaching prominently above the water. Here the formation is exposed to view in the canons and narrow passages, where the contorted strata are abruptly elevated, presenting perfect stratification and the most varied structural forms. The 'am Deposits beds maintain either a nearly vertical position, or incline with heavy dip toward the north and northeast, constituting with their upturned edges...