File:Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean (1855) (14573566009).jpg

Identifier: reportsofexplora05unit_0 (find matches)
Title: Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean
Year: 1855 (1850s)
Authors: United States. War Dept Henry, Joseph, 1797-1878 Baird, Spencer Fullerton, 1823-1887 United States. Army. Corps of Engineers
Subjects: Pacific railroads Discoveries in geography Natural history Indians of North America
Publisher: Washington : A.O.P. Nicholson, printer (etc.)
Contributing Library: San Francisco Public Library
Digitizing Sponsor: California State Library Califa/LSTA Grant

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and detached crystals of this interesting mineral, of unusual size, were abund-ant. 1 The cementing material of the mass was sand and sesqui-oxide of iron, the latter beingin quantity sufficient to give a dark color to the matrix. This peculiar conglomerate, together with the contiguous beds of sandstone, project from thetops of the hills at the same height on both sides of the river; rendering it strikingly evident,even to the most ordinary observer, that the strata were once continuous. Similar phenomenaare presented all along the slope of the Sierra Nevada, wherever the streams have cut throughthe horizontal sedimentary sandstones. At the point where we crossed the Chowchillas, below the hills just described, its banks arelow and sandy, and a broad but shallow current was running over a bed of fine sand filled withsmall glittering crystals of brown mica. There was very little river-drift of rounded stones or 1 These crystals of andalusite are described in Chapter XX. —\ i—i !3j
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ANDALUSITE—SNOW-PEAKS—GRANITE. 17 gravel in the channel, and appearances indicated that at that point the river seldom flowed as atumultuous, rapid torrent. I found numerous large and good crystals of andalusite in the sandof the banks, and some fragments of slate, also full of crystals. These may have been washedout of the adjoining conglomerate, or transported from the original sources in the SierraNevada. Ohowchillas to the Fresno, 12 miles.—From the Chowchillas to the Fresno river, outcrops ofhorizontal strata, forming low bluffs, were constantly visible. The surface is formed of sand andgravel derived from the degradation of the surrounding sandstone hills. It is almost destitute ofvegetation, and free from moisture. The reflection of the suns rays from this arid surface is ex-ceedingly oppressive ; especially when the thermometer indicates a temperature of 100° in theshade. It stood at this point during a part of the day. At the same time, the snow-capped sum-mits of the

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