. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . ourmaline, and garnet thusacted as protectors to the portions of feldspar behind and under them, while the exposed partswere most rapidly chiseled out by the sharp grains, leaving the harder minerals standing inrelief, or with the feldspar standing even with their surfaces on the lee side only, thus forming,in minature, a kind of tail, similar to the accumulations of earth and stones on the lee side ofobstructions in a current of water.
. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . ourmaline, and garnet thusacted as protectors to the portions of feldspar behind and under them, while the exposed partswere most rapidly chiseled out by the sharp grains, leaving the harder minerals standing inrelief, or with the feldspar standing even with their surfaces on the lee side only, thus forming,in minature, a kind of tail, similar to the accumulations of earth and stones on the lee side ofobstructions in a current of water. The effects produced on the vertical surfaces of the rock exposed to the wind were, perhaps, themost curious and interesting, for here the hard minerals were left standing out in points, thesofter feldspar being cut out on all sides. Masses of feldspar and quartz thus presented veryrough and uneven surfaces. A part of the rock, which was detached, is represented in theannexed figure—the projecting points being quartz, and the mass of the specimen feldspar ; thewhole having a beautifully smooth surface. ROCK, CUT BY DRIVING SAND. Direction of the wind. Where the feldspar was charged with small garnets, and was directly in front of the wind, avery peculiar result was produced ; the garnets were left standing in relief, mounted on theends of long pedicles of feldspar which had been protected from abrasion under the garnetswhile the surrounding parts were cut away. These pointed masses or needles of feldspar,tipped with garnets, stood out from the body of the rock in horizontal lines, pointing, likejewelled fingers, in the direction of the prevailing wind. They form, in reality, a perfect indexof the winds direction, recording it with as much accuracy as the oak trees in the vicinity ofSan Francisco, where, if the wind reaches them, they are bent from the perpendicular in onedirection only, or in some places lie trailed along the ground. All the little points of stonepointed west
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