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EXPOSITION AT VIENNA.
T. Materials eor Pottery.
The materials used in the manufacture of pottery were exhibited in several of the sections, notably from Japan. Much more attention has been given abroad to explorations for clays and to their examination chemically, and experimentally in the furnace, than in the United States. Collections are made under government auspices to illustrate and promote the potter’s art. The Museum of Practical Geology in London contains very full collections, illustrating the qualities of the clays and plastic strata of Great Britain, selected with a view to their applicability to ceramic manufactures. There are over one hundred and twenty-three localities represented in the series, and each set of specimens contains six examples. They are all arranged in geological sequence, commencing with the newer deposits and ranging downwards.
As already stated in the general survey, there is no lack in the United States of suitable clays for pottery. They are widely distributed, not only in recent deposits along the granite ranges of the country, but in the tertiary and older formations. They result from the gradual disintegration and decay of feldspathic rocks. This decay and softening is seen on a grand scale in the Southern States, but at the North the decayed portions appear to have been removed by the mechanical force of ice. The antiquity of the decomposition and its great extent in past geological ages, has been pointed out by Prof. T. Sterry Hunt, who believes it to have been accomplished in great part by an atmosphere of carbonic acid, aided by warmth and moisture. He connects it with the slow purification of the atmosphere which has been in progress from very early times. The alkalies, lime and magnesia, set free by the decomposition, absorbed the carbonic acid, and carried in solution to the ocean, gave rise to limestones, dolomites and common salt.
In New England the principal known deposits of clay suitable for potters’ use, are along the western base of the Green Mountains in tertiary deposits. They have been worked at Brandon, and Monkton, in Vermont. Erom the former place quantities have been taken for fire-brick and for putting into