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tinstone. 443 Geognostic Situation. It occurs disseminated, in beds, in imbedded masses, and veins, in granite, gneiss, mica-slate, clay-slate, and in an alluvial form, in what are in Cornwall named Stream nv/cs. It is associated with wolfram, tungsten, mo- lybdena, arsenical-pyrites, copper-pyrites, specular iron- ore, blende, rock-crystal, topaz, slmrl, hornblende, cb o- rite, mica, steatite and fluor-spar; less frequently with calcareous-spar, heavy-spar, and with ores of lead, silver, and iron. Geographic Situation. Europe.—Tin is not found in many different countries, but when it does occur, it is generally in considerable quantity. There are only three principal tin districts in Europe. The first and most considerable is in Cornwa 1, "’here it occurs in veins, or disseminated in gram e ttl »u slate, wneuK-i - sometimes raised in large blocks ; for we are informed by Mr Phillips, that one block raised from the mine ca ed l'olberrow in St Agnes's, weighed 1200 lbs. an pio- ductd tn ore than half that of pure metal. It is rare y found in massive portions, being generally crystallised; and it is worthy of notice, that all the varieties of form are not found indiscriminately in the same vein or set of veins, but appear rather to be distributed in different veins or sets of veins. Thus, according to Mr Phillips, the tin-mine of Pednandrae, near Redruth, affords scarce- V any other form but that of a particular kind ol twin crystal; the veins of Huel Fanny Mine, only three par ticular varieties of crystallisation ; and the tm-mine ot Eolgooth near St Austle, only minute crystals of one mrticular