Bulletin, Issues 448-454

Front Cover
U.S. Government Printing Office, 1911 - Geology
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Page 9 - I), 3J inches in diameter and one-quarter inch thick, having a 3-inch stem, which is cemented in a drill hole in• solid rock in the wall of some public building, a bridge abutment, or other substantial masonry structure. The second form (F, PI.
Page 9 - ... level. Mean sea level is the average height of the water, all stages of the tide being considered. It is determined from observations made by means of tidal gages...
Page 9 - I). The numbers stamped on the bench marks described in the following pages represent the elevations to the nearest foot, as determined by the levelman. These numbers are stamped with T^g-inch steel dies on the tablets or post caps, to the left of the word "feet.
Page 26 - FORMATION The Carbondale formation which extends from the top of the Pottsville to the top of the Herrin coal (No. 6), is about 225 feet thick in the vicinity of Carlyle. A bed of sandstone which in the lower 50 feet of this formation varies in thickness from 10 to 40 feet or more, is almost everywhere present. This rock generally contains salt water and hence is commonly included by the drillers...
Page 87 - At one place a vug was found large enough for a man to enter, lined with " smoky " quartz crystals reaching 1,000 pounds or more in weight. This would seem to indicate that the pegmatite had been intruded in a pasty or semifluid condition and that the vugs represent the spaces occupied by segregated water that was squeezed from the magma as the minerals took their final solidified form. The feldspar is an intergrowth of microcline and albite, of a brownish flesh color, beautifully fresh, and occurs...
Page 94 - ... which weighed two ounces and one dollar, besides other small pieces. Others of his party found good prospects, but none of the company had come for anything more than to ascertain the truth or falsity of the reported glad tidings and therefore were not prepared to remain and work for want of the necessary provisions and tools, but were compelled to return to La Laguna, a settlement some twenty miles above Fort Yuma, on the Arizona side of the Colorado. After their arrival at La Laguna, and report...
Page 9 - The office adjustment of the notes and the reduction to mean sea level datum may so change some of the figures that the original markings are 1 or 2 feet in error. It is assumed that engineers and others who have occasion to use the bench-mark elevations will apply to the Director of the United States Geological Survey, at Washington, DC, for the adjusted values, and will use the markings as identifications numbers only.
Page 91 - ... to the west side of the ridge. The richest ore, consisting of large masses of chalcocite with some included limestone, is encountered at a distance of 90 feet from the tunnel's mouth and continues for a distance of 21 feet as measured in the roof. There are smaller bodies of chalcocite, however, for a distance of 10 or 15 feet on either side of the main ore body. About 115 feet from the entrance to the tunnel a winze 33 feet deep was sunk in the ore, and from the bottom a drift zigzags northward...
Page 9 - Mean sea level is the average height of the water, all stages of the tide being considered. It is determined from observations made by means of tidal gages placed at stations where local conditions, such as long narrow bays, rivers, and like features will not affect the height of the water. To obtain even approximately correct results these observations must extend over at least one lunar month, and if accuracy is desired they must extend over several years.
Page 128 - Sheridan and Bear creeks the gold is mostly on bed rock, differing in this respect from that on Cub Creek, where it is found throughout the whole thickness of the 2 feet of stream gravel; on the other hand, gold from Bear and Cub creeks is light and flaky while that from Sheridan is heavy. All the gold is bright yellow in color, assaying $19.20 to the ounce. A little "white iron" pyrite is present ind also an abundance of black sand which is entirely removed by the magnet.

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