FULLERS EARTH. Two sorts of argillaceous earths are described under the name of cimolia. in catalogues of the Materia Medica, cimolia alba, sen argilla alba, Phan». Edinb. the pure white strong clay, called, from the use to which it is principally applied, tobacco-pipe-clay; and nurpurascens, (Pharm. Edin.) a compact bolar earth, commonly of a greyish brown colour, called from its use fullers earth. These have been both since expunged, and the name eipzetia would appear to have been given from Cimolus, the ancient name of an island in the sea of Crete, opposite to the promontory Zephyrus, having the same kind of soil ; hence terra cimolia, we chalk, or fullers earth, and Crctosaque rura Chnoli, Ovid ; it is now called Sicandro.
Among the useful researches for which we arc indebted to the illustriou. Bergman, lee find one upon lithomarge, or stone marl, winch seems to differ horn common marl in its composition, chiefly in possessing a much larger por tion of siliceous, and less of calcareous carom; the general characters of which are, 1st, \Veen dry, it is smor.th and slippery, like hard soap: 2dly, It is not perfectly diffusible in water; but when immersed in that Iluid, it falls into pieces of greater or less magnitude, or hi such a manner as to assume the appearance of curds: Sdly, fit the fire it easily melts into a white or reddish frothy slag, which is considerably larger than before, in consequence of its po rosity : 4thly, Its fracture is irregularly convex, or con cave. Fullers earth is one of the most useful varieties of lithomarge. Its particular characters are, that the colour is greenish white, greenish grey, olive oil green, greyish ash coloured, brown in all degrees, from very pale to almost black ; light yellowish green, or yellowish grey, passing into pale ochre yellow ; its colours are sometimes disposed in spots or stripes ; it occurs only in mass, and is without lustre ; it is very hard and firm, of a compact texture, of a rough and somewhat dusty surface ; itt: fracture is uneven, passing into large conchoidal and slaty or fine-grained; it breaks by force into indeterminate, blunt-edged, or slaty fragments; it is unctuous to the touch, not staining the hands, nor breaking easily between the fingers. it has a
little harshness between the teeth, melts freely in the mouth, adheres slightly to the tongue. It is opake, and sufficiently soft to be scratched by the nail. It takes a po lish by friction, is moderately heavy; but its specific gra vity has not been accurately ascertained: thrown into water, it makes no ebullition, or hissing, but swells gradually in bulk, and falls into a line soft powder, especially when the water is warm : it does not effervesce with acids ; before the blow-pipe it melts into a brown spongy scoria. The fullers earth of Hampshire was analyzed by Bergman, from which he obtained the following results:— The analysis of other earths included in lithomarge will be found below, under Substitutes. There appears to be two distinct formations of fullers earth; or rather two dif ferent minerals seem to be confounded under the same name. The fullers earth of Saxony belongs to the primi tive rocks, being found under strata of slaty grunstein, and passing by degrees into this very mineral ; hence it con sists of the same materials, either originally deposited in this loose state, or having acquired this consistence from decomposition. The English fullers earth, on the other hand, is always found in beds covered by, and resting upon, that peculiar and hitherto undcscribed sand-stone formation, which accompanies and serves as the foundation to chalk.
Fullers earth is found in several counties of England ; but in greatest abundance in Bedfordshire, Berkshire, Hampshire, and Sorry. For some account of this mineral in Sorry, see the article ENGLAND, VOL viii. p. 713. As a more particular account will naturally be expected under the present article, we shall consider the subject under the following heads: 1st, Particulars with regard to the coun ties of England in which it has been found ; 2dly, The mode of treatment adopted by manufacturers; Sdly, Its various uses; 4t/dy, Legal restraints ; 5thly, :Substitutes used either at home or abroad.