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acts advance angles body boiler bottom breast built called carried cars cause chute close coal connected cylinder depth diameter direction discharge distance driven engine equal face feet force formula give given gravity greater head heat hole inches inclination increased iron length less loaded longwall lower material means measures method mining minute move necessary opening operation pass pillars pipe piston pitch placed position pounds pressure produced props pump rail raise reached removed result roads rock roof rooms seam shaft shown in Fig shows side sinking slope sometimes space square inch steam strata stroke surface taken temperature thick timber track tubes turned upper usually valve vertical volume wall weight
Página 52 - Since, according to the third law of motion, every action has an equal and opposite reaction, we call that force which acts as an equal and opposite force to the pull of the string the centrifugal force, and it acts away from the center of motion.
Página 49 - of the free air actually compressed. Theoretically, this volume is equal to the area of the piston, multiplied by the length of the stroke. Actually, however, owing to imperfections in workmanship, the air does not begin to compress at the instant the piston begins its stroke. The point where the compression begins is indicated on the diagram by the
Página 16 - Lead.—A valve is said to have lead when it commences to open the steam-port just before the piston reaches the end of the stroke. The amount of lead is measured by the distance between the edge of the valve and the edge of the port from which the valve is traveling. In
Página 44 - be less steep than the slope of the valley, then the V's, as they are often termed by miners, will point upwards (see Fig. 413), those formed by the newer .beds appearing in a superior position and extending highest up the valley, as A
Página 51 - now be explained. Suppose that the body is revolved horizontally, so that the action of gravity upon it will always be the same. According to the first law of motion, a body put in motion tends to move in a straight line unless acted upon by some -^ other force, causing a change in the
Página 8 - to 54° that it took to raise the temperature from 52° to 53°. The unit quantity of heat is the quantity required to raise the temperature of a pound of water from 62° to 63°." This unit is called the British thermal unit, or BTU §18 STEAM AND STEAM-BOILERS.
Página 65 - per cent, of volatile matter, and the material volatilized includes a large proportion of burning and lubricating oils, much larger than the above kinds of bituminous coal ; whence it is extensively used for the manufacture of such oils. It graduates into oil-producing coaly shales, the more compact of which it much resembles.
Página 60 - inch face. They consist of a cylindrical box of metal, with a top of thin, elastic, corrugated metal. The air is removed from the box. When the atmospheric pressure increases, the top is pressed inwards, and, when it is diminished, the top is pressed outwards by its