Mine Gases and Ventilation: Textbook for Students of Mining, Mining Engineers and Candidates Preparing for Mining Examinations Designed for Working Out the Various Problems that Arise in the Practice of Coal Mining, as They Relate to the Safe and Effecient Operation of Mines

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McGraw-Hill, 1920 - Coal mines and mining - 433 pages
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Page 400 - A Cord of wood is a pile 8 ft. long, 4 ft. wide, and 4 ft. high ; for 8 x 4 x 4 = 128.
Page 399 - Apothecaries' weight 20 grains = 1 scruple 3 scruples = 1 dram = 60 grains 8 drams = 1 ounce = 24 scruples...
Page 329 - The logarithm of a number is the exponent of the power to which it is necessary to raise a fixed number, in order to produce the first number.
Page 403 - Distance north or south of the equator, measured in degrees, minutes, and seconds of arc.
Page 152 - ... skilled in such work, and all parts that require sterilizing shall be readily accessible for this purpose. (c) All parts of the apparatus subject to or liable to be subjected to pressures in excess of 5 pounds per square inch shall be...
Page 42 - Law states that the rates of diffusion of gases are inversely proportional to the square roots of their densities. Or...
Page 156 - Test 15 is made to determine the maximum length of time that the apparatus will supply the needs of the wearer when in a quiescent state. The wearer will remain as far as possible in a sitting posture throughout the test and perform no work. He will be allowed to manipulate the devices controlling the compressed-oxygen or compressedair supply to conserve such compressedoxygen or compressed-air supply to the greatest advantage.
Page 102 - AC, it follows, ex cequali, that as AM is to AC so is the time along AM to the time along AC. THEOREM IV, PROPOSITION IV The times of descent along planes of the same length but of different inclinations are to each other in the inverse ratio of the square roots of their heights From a single point B draw the planes BA and BC, having the same length but different inclinations; let AE and CD be horizontal lines drawn to meet the perpendicular BD; and...
Page 55 - ... the weight of an equal volume of air at the same temperature and pressure.
Page 150 - Permissibility tests will not be made unless the unit has been completely developed and is a form that can be marketed. (f) The results of the tests shall be regarded as confidential by all present at the tests and shall not be made public in any way before the shot-firing unit is formally approved by the Bureau of Mines.

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