are viscid earths, less coherent and more friable than clay; more readily uniting with water, and more freely subsiding from it. They are soft and unctuous to the touch; adhere to the tongue; and by degrees melt in the mouth, impressing a light sense of astringency. There is a great variety of these earths; the principal of which are the following:

1. Armenian bole, when pure, is of a bright red colour with a tinge of yellow: It is one of the hardest and most compact bodies of this class, and not smooth and glossy like the others, but generally of a rough and dusty surface. It does not effervesce with acids, though some part of it is dissolved by all of them. Neuman observes, that four ounces of Armenian bole distilled in a glass retort in an open fire, yielded three drachms of a saline phlegm, which smelt a little urinous, and changed syrup of violets green. In the neck of the retort was found a little powdery saline matter which had an ammoniacal taste, but it was in too small quantity to be collected or further examined. Like most other coloured earths, this kind of bole contains a portion of ferruginous matter, to which the colour is owing; and which may be separated by the magnet, after the bole has been calcined with oil or other inflammable matters. It is likewise impregnated with vitriolic acid; and hence, when mixed with nitre or sea salt, it extricates the acids of these salts in the fire.

2. French bole is of a pale red colour, variegated with irregular specks of white and yellow. It is much softer than the Armenian, and slightly effervesces with acids.

3. Bole of Blois is yellow, remarkably lighter than most of the other yellow earths, and effervesces strongly with acids.

4. Bohemian bole is of a yellow colour, with a cast of red, and generally of a flaky texture. It is not acted on by acids.

5. Lemnian earth is of a pale red colour, and slightly effervesces with acids.

6. Silesian bole is of a pale yellow colour, and acids have no sensible effect upon it.

These and other earths, made into little masses, and stamped with certain impressions, are called terrae sigillatae. They have been recommended as astringent, sudorific, and alexipharmic; but these and many other virtues that have been ascribed to them appear to have no foundation. They are still, however, prescribed in fluxes and complaints of the prime vice.