Page:The New International Encyclopædia 1st ed. v. 09.djvu/327

* GRIND AL. 289 GRINDING AND CRUSHING. establishment of the Anglican system, and he was transferred to the See of Y'ork in ir)7l). On the death of Archbishop Parker, Queen Eliza- beth favored his accession to the See of Canter- bury, to which he was elected in 1575. The Queen had counted on his traetability, but was dis- appointed to find him rigidly conscientious. He was sequestered in 1577. and was not fully Re- stored for five years. His writings, and a life by the Kev. William Nicholson, were published by the Parker S.icicty in 1853. GRINDELWALD, grin'drl-valt. One of the most Iwautiful valleys of the Bernese Alps, situ- ated in the eastern part of the Canton of Bern (Map: Switzerland, C 2). It is celebrated for its glaciers, the Lower Grindelwald descending lower than any other of the Alpine glaciers. Grindelwald is a favorite winter resort. The village is situated at an altitude of about 3500 feet, and has a number of hotels. Its population was ,3370 in HtOO. GRINDER (from grind, AS. grindan ; ulti- mately connected with Lat. frcttderc, to gnash). A small Australian llyeateher {Sisura inquieta) which, besides its ordinary whistle, produces a sound resembling that made by a scissors-grind- er's machine. This sound is made while the bird hovers in the air (its whole manner of flight is remarkable), but how it is produced is not known. GRINDING. The operation of shaping or snioolliiiig any hard substance by rubliing away its surface with a rough stone or with a cutting powder. It is similar to fding. and is used in cases where, from the hardness of the material, or for other reasons, filing is inapplicable. Thus cutting tools and other steel instruments may be filed before hardening and tempering; but after this, if further abrasion is required, they must be ground. Glass lenses and metal specula .are ground into shape with emer.y-powder laid upon a metal tool. Ornamental glass is ground into facets or otherwise by mcijns of stones and lap- wheels. Diamonds and other gems are ground or cut with diamond-dust imbedded in soft iron. When large flat surf.aces are required, they are obtained by first working two pieces of the sub- stance nearly flat, and then laying one upon the other, and grinding their surfaces together with sand, emer^', or other suitable cutting powder. Plate glass is finished in this manner; also sur- faces of cast iron where accurate fitting is re- quired, the iron surface being either prepared with a planing-machine or by turning in a lathe. Sockets and other bearings which require to be fitted with great. accuracy are usually finished by grinding together. For brass and bell-metal jjow- dered pumice-stone is best adapted for such pur- poses, as emery is liable to imbed itself in the metal and give it a permanent cutting action upon the bearings. Drij grinding is the term applied to the grinding of steel with dry grind- stones. Its principal applications are in the grinding of the points of needles and forks, the surfaces of gun-barrels, and in finishing steel pens, Sae Gkinding and Cru.siiing Machinery; CUTLKRY. GRINDING AND CRUSHING MACHIN- ERY. Under this head are included various forms of apparatus for reducing hard or fibrous substances to fragmentary form or to fine powder. Generally speaking, crushing machines are em- jdoycd for performing the coarse reduction, and a])paratus for producing a fine powder or flour is termed grinding machinerj'. The two classes merge into each other, but it will add to clear- ness of treatment in some respects to consider them separately in this article. Fig. 1. VERTIC-L SECTION OF STAMP MILL FOR CRUSHING GOLD ORE. Cri^shing Machinery. Perhaps the earliest form of crushing machine is the stamp or stamp mill, which is now so extensively emploj'ed in reducing gold, copper, and other ores. Briefly described, a stamp mill consists of one or more stamps beneath which the ore is fed in a thin stream. Each stamp consists of a stem carrying at its lower end a head of chilled cast iron and arranged to work vertically up and down be- tween guides. To produce the vertical movement there is a bracket or lug attached to the stem with ^iiich a cam or scries of cams moiuited on horizontal shafting engages, and thus raises and releases the stamp. In reducing ores stamps are usually operated in batteries or groups. Stamp mills perform either coarse or compara- tively fine crushing, according as the rate of feed is fast or slow. Sometimes positive pressure stamps are employed in place of gravity stamps. lioll crushers are another imjjortant type. In them the material to be crushed is passed be- tween two or more vertical rolls which may or maj' not have corrugated surfaces. Sometimes the rolls are designed to have a slipping action with reference to each other. Roll crushers are used in crushing sugar-cane and other fibrous materials particularly. Edge -runner crushers are usually employed in crushing seeds for oil. (ienerally they consist of a vertical axle which carries two or more radial arms, on the ends of which .are journaled heavy metal wheels with broad tires or edges. These wheels through the rotation of the vertical axle travel round and round in a circular track on the bottom of a