See also:peculiar kind of
See also:lignite or
See also:anthracite; often cut and polished for ornaments . The word "
See also:jet " probably comes, through O . Fr. jaiet, from the classical gagates, a word which was derived, according to Pliny, from Gagas, in
See also:Lycia, where jet, or a similar substance, was originally found . Jet was used in Britain in prehistoric times; many
See also:round barrows of the
See also:Bronze age have yielded jet beads, buttons, rings, armlets and other ornaments . The abundance of jet in Britain is alluded to by Caius
See also:Solinus (fl . 3rd century) and jet ornaments are found with
See also:relics in Britain . Probably the supply was obtained from the
See also:coast of
See also:Yorkshire, especially near
See also:Whitby, where nodules of jet were formerly picked up on the
See also:shore . Caedmon refers to this jet, and at a later date it was used for
See also:rosary beads by the monks of Whitby Abbey . The Whitby jet occurs in irregular masses, often of lenticular shape, embedded in hard shales known as jet-
See also:rock . The jet-rock series belongs to that division of the Upper
See also:Lias which is termed the zone of
See also:Ammonites serpentinus . Microscopic examination of jet occasionally reveals the structure of coniferous
See also:wood, which A . C .
Seward has shown to be araucarian . Probably masses of wood were brought down by a
See also:river, and drifted out to
See also:sea, where becoming
See also:water-logged they sank, and became gradually buried in a deposit of
See also:fine mud, which eventually hardened into shale . Under pressure, perhaps assisted by
See also:heat, and with exclusion of air, the wood suffered a peculiar kind of decomposition, probably modified by the presence of
See also:salt water, as suggested by Percy E . Spielmann . Scales of
See also:fish and other fossils of the jet-rock are frequently impregnated with bituminous products, which may replace the
See also:original tissues . Drops of liquid
See also:bitumen occur in the cavities of some fossils, whilst inflammable
See also:gas is not uncommon in the jet-workings, and petroleum may be detected by its smell . Iron
See also:pyrites is often associated with the jet . Formerly sufficient jet was found in loose pieces on the shore, set
See also:free by the disintegration of the cliffs, or washed up from a submarine source . When this supply became insufficient, the rock was attacked by the jet-workers; ultimately the workings took the
See also:form of true mines, levels being driven into the shales not only at their outcrop in the cliffs but in some of the inland dales of the Yorkshire
See also:moor-lands, such as Eskdale . The best jet has a
See also:uniform black
See also:colour, and is hard, compact and homogeneous in texture, breaking with a conchoidal fracture . It must be tough enough to be readily carved or turned on the
See also:lathe, and sufficiently compact in texture to receive a high
See also:polish . The final polish was formerly given by means of
See also:rouge, which produces a beautiful velvety
See also:surface, but rotten-
See also:stone and lampblack are often employed instead .
The softer kinds, not capable of being freely worked, are known as
See also:bastard jet . A soft jet is obtained from the estuarine series of the
See also:Lower Oolites of Yorkshire . Much jet is imported from Spain, but it is generally less hard and lustrous than true Whitby jet . In Spain the chief locality is
See also:Villaviciosa, in the province of
See also:Asturias . France furnishes jet, especially in the department of the
See also:Aude . Much jet, too, occurs in the Lias of
See also:Wurttemberg, and
See also:works have been established for its utilization . In the
See also:United States jet is known at many localities but is not systematically worked . Pennsylvanian anthracite, however, has been occasionally employed as a substitute . In like manner Scotch cannel
See also:coal has been sometimes used at Whitby . Imitations of jet, or substitutes for it, are furnished by vulcanite,
See also:glass, black
See also:obsidian and black
See also:onyx, or stained chalcedony . Jet is sometimes improperly termed black
See also:amber, because like amber, though in less degree, it becomes electric by
See also:friction . See P .
E . Spielmann, " On the Origin of Jet," Chemical
See also:News (Dec . 14, 1906) ; C .
See also:Fox-Strangways, " The
See also:Jurassic Rocks of Britain, Vol . I . Yorkshire," Mem . Geol . Sure . (1892); J . A .
See also:Bower, " Whitby Jet and its Manufacture," Journ .
See also:Soc .
Arts (1874, vol. xxii. p . 8o) .
JETHRO (or JETHER, Exod. iv. 18)
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