Bulletin of the United States Geological SurveyThe Survey., 1909 |
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Palavras e frases frequentes
50 per cent Alabama amount anthracite Appalachian approximately Arkansas auriferous average belt bituminous coal by-products California carbonate Clinton coal beds coal fields coke Colorado contain Cook Inlet copper County deposits depth developed discovery distribution district drilling estimated exhaustion extent feet fuel furnaces future Geological Survey gold grade hematite high-grade Illinois important industry iron-ore Kentucky known Lake Superior lands lead lignite limestone lode Long tons low-grade magnetite Matanuska metal mineral mining Missouri Mountain natural gas occur Ohio original supply ounces outcrop output ovens Pacific peat Pennsylvania petroleum phosphate phosphate rock placer placer mining pounds present Prince William Sound probably production in 1907 province quantity rate of increase region reserves River sandstones Seward Peninsula shales short tons silver southeastern Alaska square miles Tennessee Territory thickness tion tonnage total production United Utah utilization waste West Virginia western Wyoming yield Yukon zinc
Passagens conhecidas
Página 20 - ... one of the coal-producing States which has within its borders areas belonging to any two of the great coal fields. The eastern counties of the State are underlain by the coal beds of the great Appalachian system...
Página 11 - The principal loss or waste attending coal-mining operations is that represented by the quantity of coal necessarily left in the ground as pillars to support the roof. In some cases it is also necessary to leave a foot or more of coal as a part of the roof, because of the unstable character of the material overlying the coal, which itself does not make a good roof. It has also been frequently the case that, where portions of the coal bed have been of inferior quality, only the high-grade coal has...
Página 11 - On the other hand, powerful influences will come to bear upon coal production, which favor lengthening the life of the supply. Thus it is to be hoped that with more improved methods in the utilization of coal the increased efficiency per unit may act as a factor in reducing coal consumption, and improved mining methods should likewise decrease the waste percentage. The increased utilization of water power should also tend to decrease coal consumption. Again, as soon as the end appears in sight prices...
Página 12 - So far as underground workings are concerned, there has been no revolution in the methods employed since that time, but there has been a considerable improvement in the application of those methods, which has resulted in the recovery at the present time of a materially larger proportion of the coal in the ground than was the rule at that date. The earlier methods of mining consisted in leaving comparatively narrow pillars, and in the mining of large rooms the result was that the pillars were not...
Página 160 - Miocene age, and consists of so-called pebble rock which is in fact a solid mass from which the calcium carbonate has been leached out and partially replaced by phosphate, leaving cavities which connect and penetrate through the rock, giving it the appearance of being made up of separate pebbles. The rock runs from 1 to 3 feet in thickness, and is overlain by a greensand marl.
Página 163 - There are in the series several other beds ranging from a few inches to 10 feet in thickness, and separated by thin beds of limestone or shale. Usually one and sometimes two of these beds at a given section are workable, and probably some of the others will eventually be mined. The lime phosphate content in the workable beds varies from 65 to 80 per cent, with an average of 72 per cent.
Página 15 - Geological Survey. In such cases careful estimates have been made, based upon the average surplus gas obtained from similar coals used at ovens of the same type. The value, similarly estimated, has been placed at from 10 to 15 cents per thousand cubic feet. The coal consumed in retort ovens in 1907 amounted to 7,460,587 short tons.
Página 17 - State is estimated at 14,430 square miles, and the original coal supply is estimated to have been 68,903,000,000 short tons. The exhaustion to the close of 1907 represents a little over 0.3 of 1 per cent, and the production in 1907 was a little over 0.02 of 1 per cent of the estimated original supply. Arizona. — A small area of 30 square miles in Arizona is estimated to contain 60,000,000 tons of coal, from which there had been no production at the close of 1907. Arkansas. — As in Alabama, the...
Página 12 - ... time of a materially larger proportion of the coal in the ground than was the rule at that date. The earlier methods of mining consisted in leaving comparatively narrow pillars and in the mining of large rooms, the result being that the pillars were not strong enough to stand the pressure and they were crushed beyond recovery. It is now customary to use larger pillars between the rooms, which makes it possible to better control the roof during "robbing" operations and to eventually recover a...
Página 159 - The hard rock occurs both as bedded rock and as a bowlder deposit in a soft matrix of phosphatic sands, clays, and other materials. The thickest bed known is at least 20 feet thick, and possibly much more than that. The bowlders in the bowlder deposits vary in size from a few inches up to 8 or 10 feet, and lie embedded in all positions, surrounded by sand and clay containing more or less phosphate of lime in finer particles, resulting from a general distribution of the disintegrated portions of the...