Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/146

134  1em  HONE. Under the name of hones, whetstones, or sharpening stones, a variety of finely siliceous stones are employed for whetting or sharpening edge tools, and for abrading steel and other hard surfaces. They generally are prepared in the form of flat slabs or small pencils or rods of the material, but some are made with the outline of the special instrument they are designed to sharpen. Their abrading action is due to the quartz or silica which is always present in predominating proportion, some kinds consisting of almost pure quartz, while in others the siliceous element is ver} r intimately mixed with aluminous or calcareous matter, forming a uniform compact stone, the extremely fine siliceous particles of which impart a remark ably keen edge to the instruments for the sharpening of which they are applied. Hones are used either dry, with water, or with oil, and generally the object to be sharpened is drawn with hand pressure backward and forw r ard over the surface of the hone ; but sometimes the stone is moved over the cutting edge. The coarsest type of stone which can be included among hones is the bat or scythe stone, a porous fine-grained sandstone used for sharpening scythes and cutters of mowing machines, and for other like purposes. Next come the ragstones, which consist of quart/ose mica- schist, and give a finer edge than any sandstone. Under the head of oilstones or hones proper the most famous and best-known qualities are the German razor hone, the Turkey oilstone, and the Arkansas stone. The German razor hone, used, as its name implies, chiefly for razors, is obtained from the slate mountains near Ratisbon, where it forms a yellow vein of from 1 to 18 inches in the blue slate. It is sawn into thin slabs, and these are cemented to slabs of slate which serve as a support. Turkey oilstone is a close- grained bluish stone containing from 70 to 75 per cent, of silica in a state of very fine division, intimately blended with about 20 to 25 per cent, of calcite. It is obtained only in small pieces, frequently flawed and not tough, so that the slabs must have a backing of slate or wood. It is one of the most valuable of all whetstones, abrading the hardest steel, and possessing sufficient compactness to resist the pressure required for sharpening gravers. The stone comes from the interior of Asia Minor, whence it is carried to Smyrna. Of Arkansas stones there are two varieties both found in the same district, Garland county, Arkansas, United States. The finer kind, known as Arkansas hone, is obtained in small pieces at the hot springs, and the second quality, distinguished as Washita stone, comes from Washita or Ouachita river. The hones yield on analysis 98 per cent, of silica, with small proportions of alumina, potash, and soda, and mere traces of iron, lime, magnesia, and hydrofluoric acid. They are white in colour, extremely 