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Encyclopedia Britannica - Main :: PYR-RAY |
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QUARRYING , the art of winning or obtaining from the earth's crust the various kinds of stone used in construction, the operation being, in most cases, conducted in open workings. According to their composition, building stones are broadly classed as granites, sandstones, limestones and slates. Under the first of these heads is included a number of crystalline rock species, such as granite, syenite
chief
block
Berea
The methods of quarrying vary with the composition and hardness of the rocks, their structure, cleavage, and other physical properties; also with the position and character of the deposits or rock-masses. The general pur- Method: employed. pose of the work is to separate the material from its bed in masses of form and size adapted to the intended use. Cutting the stone to accurate dimensions, dressing, rubbing and polishing are subsequent operations not involved in quarrying. The practice of quarrying consists in uncovering a sufficient surface of the rock by removing superficial soil, sand or clay, or by sinking a shaft or slope, and then with proper tools and, when necessary, with explosives, detaching blocks of form and size adapted to the purpose in view. Frequently the outer portion of the rock has been affected by the action of the weather and other atmospheric agencies, so that it has become discoloured or softened by decay. This weathered material must be removed before stone can be obtained for use. A quarry should, if possible, be opened on a hillside, for in this case it is usually much easier to dispose of the water which necessarily collects in any deep excavation, and which, if drainage by gravity is not afforded, must be removed by pumping, at considerable expense. As it is generally most convenient to operate on a vertical face of rock, the preliminary work of opening a quarry is usually directed toward the production of this result; but its accomplishment involves the waste of a certain amount of stone, which must be broken into irregular and useless pieces. The separation of blocks of building stone is effected ordinarily by drilling holes along the outlines of the block
horizontal
the explosion of the powder. In the absence of compressed air, of the " coffin " of a horse's foot; in bootmaking, to the side water under pressure may be used and also small powder charges piece of leather reaching from the vamp to the heel. The exploded at intervals of a few days. In thinly bedded sandstones, " quarter " of a ship is the after part of her side from the main-where vertical joints are frequent, it is often possible to separate chains to the stern (see QUARTERDECK). the desired slabs and flagstones with crowbars and wedges, There has been much discussion as to the origin of the use of the without drilling or the use of explosives. When blasting is word " quarter " in the sense of mercy, clemency, the sparing of necessary, some form of gunpowder is generally used, rather the life of a beaten enemy and the acceptance of his surrender. than a violent explosive like dynamite, in order to avoid shatter- The same use is found in Fr. quartier. Cotgrave explains this word ing rock. This, however, applies only dimension stone. as faire war, wherein souldiers are taken prisoners and ransomed g P- to at a certain rate." The he real origin cannot be, as has often been When the production of broken stone for road-making, concrete, repeated, following De Brieux (Origins de plusieurs fagons de parler, or similar purposes is the sole end in view, violent explosives are 1672), that it was due to a supposed agreement between the Dutch preferred. In limestones and marbles
stones, channelling machines, driven b steam, are employed, their pay. The true source is either the assignment of " quarters," g by i.e. lodgings, to captured prisoners whose lives were spared, or the by which vertical or oblique grooves or channels can be cut use of the word, now obsolete, for relations with or conduct towards with great rapidity to a depth of several feet. A level bed of another, often in the sense of fair treatment; thus in Bacon's Essay rock is cleared, and on this are laid rails, along which the machine on Cunning, "two, that were competitors, ...kept good quarter moves. After the channels are cut, a row of holes is bored between themselves." Quarter days are the days that begin each quarter of the year. perpendicular to the former at the desired distance below the In England they are the 25th of March (Lady Day), the 24th of surface of the bed, and by driving wedges into these the required June (Midsummer Day), the 29th of September (Michaelmas Day) blocks are separated. and the 25th of December (Christmas Day). They are the days When the beds of stone to be quarried are thin, and when to on which it is usually contracted that rents should be paid and houses or lands entered upon or quitted. In Scotland there are remove the whole of the overlying mass of earth or rock would two legal terms, the 15th of May (Whitsunday) and the uth of be too expensive, it is found convenient to treat the November (Martinmas); these, together with the two conventional Mince. as if it were a mine, and to rely upon on methods terms, 2nd of February (Candlemas) and the 1st of August (Lammas), stone. quarry y P make up the Scottish quarter days. In the Scottish burghs, however, similar to those practised in mining. A horizontal
bed of rock is usually opened at its outcrop on some hillside, or In the United States the quarter days are, in law, the 1st of January, if this is impracticable, as shaft or slope is excavated to reach it. April, July and October. If dimension stone is required, a deep horizontal groove is cut QUARTERDECK, the after part of the upper deck of a ship. near the top or the bottom of the bed. The quarry face is then In former times the upper deck of a line-of-battle ship or frigate divided into blocks by saw-cuts, channels, or rows of drill
would be more expensive. At some of the marble quarries in QUARTER SESSIONS, COURT OF, in English law, the name Vermont, U.S.A., where the strata are very nearly vertical, the for the justices of the peace of any county, riding, parts, division beds are worked to a great depth with a comparatively small or liberty of a county, or of any county of a city or county of a surface opening. town, in general or quarter sessions assembled; it includes the See G. P. Merrill, Stones for Building and Decoration (New York
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