128 
EXPOSITION AT VIENNA. 
Y. Materials eor Pottery. 
The materials iised in the manufacture of pottery were ex- 
hibited 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 represe.nted in 
the series, and each set of specimens contains six examples. 
They are all arranged in geological sequence, commeuciug 
with the newer deposits and ranging downwards. 
As already stated in the general sui-vey, 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 mc- 
chanical 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 accom- 
plished in great part by an atmosphere of carbonic aeid, aided 
by warmth and moisture. He connects it with the slow puri- 
fication 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 riso to limestones, dolomites 
and common salt. 
In New England the principal known deposits of clay suit 
able 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. From the former place 
quantities have been taken for fire-brick and for putting into