[74 ECONOMIC GEOLOGY

tension; and as the material is not plastic it remains friable
so that all the surface is reached by the liquid that is being
filtered. England formerly produced the largest quantity,
which mainly came from a bed known as “the Fuller's
Earth ” in the Lower Oolite of Wiltshire. Its existence led
to the establishment there of the early woollen industry.
The second important English deposit is in the Lower Green.
sand of Nutfield and Reigate in Surrey. In America Florida
earth is largely used for the discoloration of oils. .The
American fuller’s earths are very varied in character and
origin ; that in Arkansas occurs in veins formed by the alteration
 of basalt dykes; the Bentonite of Tennessee is an
altered volcanic ash; that of Massachusetts is a glacial silt.
The production of fuller's earth in* England in recent
years has varied from about 20,000 to 30,000 tons, and its
price has been about £2 per ton.