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Veins. ' ^39 9 » t_ 11. Veins alfo occur mote frequently M flat hilly country, than in fteep mountainous country, and generally on the ridges of the hills. Beds, oil the contrary, areequally, if not more abundant, in fteep mountainous country. ! 12. Sometimes the ftrdta or beds, traverfeiVby 1 veins, are merely feparated ; fo that the ftva'th’dif beds on oppoliTe : ftdes of the vein correfpond.' In other cafes, there is a diflocation, or what millers call a Jhift of the ftrata, t*hat is the firin!« J ftr&& or beds on o\>poftte tides ofthe vein, do not 1 Lottes fpond, but are depreffed or funk on the har^rng or tiller fide of'rhe ! vein. The degree of 'de^Aton 6'r'difl icirtiort d lira Hycorrefpo nets to thehiaghitude i’ ,j • :;u‘-:"V :ii 2 31 lift ft ot the’Vein’. 13. The wttllfe of veins are' frequently mobe 0# lefs altered ;"arr&' ; this alteration is caofedu'eitlielf by in interrhrxitrre of the materials ot dhe”veiri with that of tlifc wall *, or- by a decompoftttoft-of the wall, owing'to the agency of- pCrcolutjng Wa-i trr, or the fubft&nces of which 1 the vainhs.cdmpoa fed. "-'■Z, * When veins of greenftone, porphyry-flate, 6r hthef fimilai locks, traverfe certain kinds of fandllcne, the walls bf the vtins are obfeived to be- more conipatt than the fandllone at a ditlanoe. This increafe of hardnefs is-cau, fed by a portion of the matter of the vein being intermix? cd with the fandllone in contact with it. Excellent ex amples of this appeaianre occur in the ifland of Arian. Metalliferous veuw foiuc times induce a liuular cuapge ,ou their wails.