Part I—The Geologic Column.

Reconnoissance of the California Survey. — The Taylorville region of Plumas county, California, lies in the Sierra Nevada immediately north of the fortieth parallel. Reconnoitering parties of the California geological survey passed through the region in 1861 and 1863* and observed slates and sandstones, sometimes hut little metamorphosed, also hard lava and granitic masses, and reported that “This part of the country is principally occupied by the metamorphic rocks over an area of about thirty miles in diameter.” It is “Almost entirely surrounded by volcanic materials, the great lava streams which have come down from Lassen peak on the north and Pilot peak on the south uniting with the volcanic crest of the Sierra so as to cover the slates around three-quarters of the circumference of the circle.” The state survey party in 1863 consisted of Messrs Brewer and King, who made two very important . . .

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