Page:The New International Encyclopædia 1st ed. v. 16.djvu/677

* QUARRY. 593 QUARTER-DAYS. cylindrical hole, and '03- driving the plug dorni between the feathers it exerts a splitting or cleav- ing force of great intensity. In quarrying, as fii-st stated, each hole in a long row is filled with a plug and feathers; by striking each plug a sharp blow with a hammer, hitting theni in suc- cession, and b.y repeating the operation again and again, the combined splitting force of the plugs and feathers finally becomes great enough to rup- ture the rock. Generally the plugs and feathers are used only tor effecting the larger subdivisions of the rock, the smaller pieces being split and broken by hammers and wedges. Sometimes tliis method of quarrying is called the plug and feather method. Explosives are the means most commonly em- ployed for detaching large blocks of stone in quarries, these blocks being afterwards split and l)roken into smaller stones by wedges or by the plug and feather method. In tliis method of quarrying the drill holes are put down to the depth to which it is required to break the rock and are then partly filled with some explosive, which is discharged by the usual metliods of blasting (q.v. ). The kind of explosive used ■depends upon the character of the result which is sought. In quarrying rock to be crushed into small fragments for road work, concrete making, etc., the object sought is a rather finely hroken mass of stone, and here, because of its great shattering effect, some form of Iiigh explo- sive, as dynamite, is employed. When building stone of large size is to be quarried, weaker and slower acting explosives, as gunpowder, are em- jfloyed. In eacli quarry the structure of the rock has to be carefully studied with the view of taking advantage of the cleavage planes and natural joints, and for each class of rocks there is a characteristic method employed. The drill holes are usually made by rock drills operated In' power, though hand drills and churn drills are also used. The drill holes are driven vertically in a row some distance back of and parallel to the edge of the working face of the quarry, and are blasted simultaneously so as to force outward a rectangular mass of rock. Channeling is the process of cutting long narrow channels in rock to free the sides of large blocks of stone. Channeling machines, or channelers, are made in a variety of forms, the most common of which is a vertical steam boiler mounted on wheels and provided with mechanism for self- propulsion, having on the same carriage with the ijoiler a steam cylinder which operates, like a percussion drill, a flat bar with a cutting edge. In operation the machine is run forward and back so as to carry the cutter back and forth along the line on which the channel cut is to be made. If the rock is in layers the channel cut is often not made the full depth of the layer, but is sunk deep enough to permit the insertion of wedges by which the rock is split, the cut or groove guiding the fracture. ^Yhen the rock is not in layers it is often necessary to undercut the block as well as to cut a channel around it. This is done by drilling a series of holes along the hottom, the process being called gadding by quarrymen. Wedges inserted in the drill holes serve to separate or split the rock at the bot- tom. A special form nf machine called a gadder is used for undercutting. It consists essentially of a rotary drill, generally a diamond drill, ar- ranged to be operated horizontally and receiving motion from an engine taking steam from a vertical boiler, the whole being mounted on a carriage. The channeling and wedging process of quarrying is extensively used in quarrying marble, sandstone, limestone, and the other softer rocks, but is not a successful process for granite and other similarly hard stones. For a descrip- tion of the methods and tools used in cutting quarry stone into suitable shapes for structural purposes, see Stone Ci'tting a.xd Dre.ssi.xg. For full details of quarrying processes and machin- ery, consult Merrill, atones for Building and Decoration (Xew York, 1891), and Report on the Quarry Industry, vol. x.. Tenth United States Census. See illustration vith the article Mar- ble ; also the articles Building Stone; Dbill; Explosives. QUARTAN FEVER. See Malaria and Malarial Fever. QUARTER. See Weights and Measures. QUARTER-CRACK. A form of sandcraek, a disease of the horse; specifically a vertical crack on the lateral part of the wall of the foot. When the crack is directly in front it is called a toe crack. Toe cracks are most common in the hind feet, while quarter-cracks nearly always affect the fore feet and similarly the inside quar- ter is more liable to the injury than the outside one, in that when in motion it is subject to a greater part of the weight of the horse. In the normal foot the coronet or, for authorities differ, the sensitive lamina", which cover the external surface of the pedal bone, secretes an adhesive material whieh binds firmly together the fibres of the wall of the hoof. When the secreting mem- brane is prevented from carrying out its func- tions the material secreted under such conditions loses its power, and the horn which it supplies becomes deficient in strength. Where this disease is of hereditary tendency the horn is so weak that it would seem to split, if subjected to a violent strain. Ordinarily, the various forms of sand- crack are caused by the nuich to be condenmed system of using seated shoes and of paring the frog, an unnatural custom b.v which the entire weight of the animal is thrown on the crust of the foot, instead of being properly distributed be- tween the wall, the frog, the outer jiortion of the sole, and the bars. Among other causes of per- verted secretion may be mentioned the strain of fast work, and hard ground. Cracks or splits naturally occur in that part of the hoof which receives the greatest amount of strain, usually the inner quarter of the fore, and the toe of the hind foot, although it sometimes cracks at the toe of the fore foot, if the hoof is of a flat conformation. Cart and cab horses are especiallj' liable to sand- crack. The usual treatment is : ( 1 ) To prevent movement between the edges of the crack ; ( 2 ) to heal the exposed tissues should they be wounded or inflamed ; and ( 3 ) to encourage the downward growth of sound horn from above the crack, for it is evident that as the edges of the crack cannot remiite the growing down of the crack is the only effective remedy. An authoritative and comprehensive treatment of this subject may be found in Hayes. Veterinary otes for Horse Oirners (London. 1S97). QUARTER-DAYS. Conventional dates on which, by custom or agreement, leiises begin and