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BOOK II
29
be white such as that from the village of Hasda in Hildesheim. This white earth is sometimes stained red. These earths are usually harsh.
I shall discuss now the use of earths in medicine. All, since they are naturally dry, possess the power of drying. Earth, in general, is astringent and cooling and breaks up infections. The most astringent earth is the coolest. Some earths are so astringent that they will tear the skin from the tongue when placed on it. The greenish earth found at Linda, Ha­nover, belongs to this class. Some earths are not so astringent and others only moderately so. An acrimonious earth has a taste characteristic of heat. It warms the skin and usually the more acrimonious it is the more it heats. One which is so weakly acrimonious that the senses cannot detect it, warms very slightly and produces no biting or pain although it cleans­es. Some earths with an oily taste feel like glue on the tongue and while they are neither astringent nor acrid they may be used as an ointment and cool the skin moderately. Any earth that is either warm or cool to the skin and can be spread may be used as an ointment. With an increase in unc-tuousness it becomes warmer or cooler. An unctuous, astringent earth may be used as an astringent ointment and an unctuous, acrid earth as a cleansing ointment. Only by careful study of the simple earths which come to hand can one judge accurately the uses to which they are best adapted.
I shall now discuss earths which have taken their names either from the locality in which they are found or from their color and shall attempt to describe their various properties. This is not difficult in some instances since various writers describe certain properties by which one earth is distinguished from another. In other instances it is very difficult since writers have described the medicinal properties of the earths and make no mention of any others.
There are two varieties of Samian earth, one called collyrion because it is commonly used in eye remedies which are called collyria by the Greeks. The other earth is called aster. The origin of the latter name is not def­initely known but may come from the star (αστήρ) with which the earth is stamped when placed on the market just as the Lemnian earth is stamped with a goat. The name may come from the large amount of glistening mica. Mica is also common in the Eisleben clay. Both of the Samian earths are used in medicine. Dioscorides preferred collyrion to aster while Galen preferred aster for some diseases and collyrion for others. The latter is an unctuous, porous, white, soft earth with an oily-sweet taste. Being unctuous it is also glutinous; being porous it is light; being soft and dry, friable. Dioscorides writes that it is glutinous and the taste is obvious when placed on the tongue. He observes that glutinous earths are always unctuous and porous earths are light in weight since they can hold a large quantity of air throughout their mass and this is the cause of the lightness. He describes the earth as soft and easily crushed which indicates that it is dry. Finally he says it has a good taste, meaning oily-sweet, which is observed when the earth is placed on the tongue and dis-