The mining district is coverd with a thin growth of scrub oaks and yellow pine. The earth is divested of soil, except sparingly in some of the valleys, being of a reddish color, by the decomposition of rocks containing iron.
The climate is so dry during summer, that little grass grows in any part of the mines. Nauseous exhalations are therefore excluded, and the atmosphere is quite healthy. In some parts of the mines the miners become sick, but it is mostly attributable to their treatment with themselves. Through the summer months, the days are warm but the nights are cool, and but few nights occur in which a man does not need considerable night clothing toward morning.
The Geology of the Gold District of California, with the probable cause of the production of Gold to the surface of the earth.
The rocks of Golden California, in common with the whole western declivity of the Sierra Neveda mountains, are principally composd of primary, stratified, slate rocks. Some of these rocks are talcose slate. Others are more silicious, approaching even to coarsish sandstone slate, of various colors.
Before confining the reader expressly to the gold district, a few remarks relative to that portion of California lying west of the Neveda mountains to the valley of the great Sacramento and St. Waukeen, may afford some light on the subject of that part of the western declivity lying within the seat of mining operations. The slate rock on the western side of the mountain range, from its axis to its base, is tilted up a little more than perpendicularly outward from the axis of the mountain, a distance of more than 60 miles in width, and traverses the whole range, as far north and south as the present mines extend, in lines parallel to the course of the mountain’s axis.
At the base of the mountain, commences a tertiary deposit of about 20 miles in width, which, with an alluvial deposit of about 20 more in width, to the great rivers of the valley, hides from sight the remaining portion of tilted rocks, so that the entire width of the tilted strata can never exactly be ascertaind. But if a mountain range like the one under consideration, is formd by the furrowd and ridgd condition of the earth’s crust, by conforming to a diminishd molten nucleus within, from refrigeration of its heat, it may be expected that the whole declivity, from its axis or highest point to its lowest or mid valley, may be all of it tilted up in the same manner as that portion which is presented to sight. If this be fact, we are then apprizd that a portion of the earth’s crust must have had a thickness of full 100 miles, by measuring across the tilted rocks, from the central valley, to the top of the mountain, eastward,—a fact not hitherto believd by geologists, from experiments made upon the increase of downward heat, to where the crust must necessarily become molten.