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Book II About different applications of earths (painting, medical) and their occurrences

Book II About different applications of earths (painting, medical) and their occurrences Page of 251 Book II About different applications of earths (painting, medical) and their occurrences Text size:minus plus Restore normal size   Mail page  Print this page
BOOK II
25
while the earthy varieties are smooth or intermediate. Marls differ in form. Some form crusts, usually earthy and rarely stony. Tufaceous varieties are porous, sometimes with openings like pipes that extend through the entire body. The purer the marl the better it is for fertilizing and the harder it is the longer its action. Some of the hard varieties are richer than others. Soils can be made fertile for many years by either applying a large amount at one time or small amounts over a period of time. Softer varieties are best for dry soils, harder varieties, arenaceous, tufaceous, or stony, for moist soils. In Greater Germany only the farmers in Saxony use it. Some of the fields in Thuringia and Bohemia are too fertile. When manure is abundant the farmers prefer to use it.
Marl does not occur in some of our mountainous districts. It is quarried in many places in Saxony, namely, between Mundar and Cassel, a town in Hesse, where it has a variety of colors; an iridescent variety in western Hildesheim near the Indersta river at the foot of a hill; white tufaceous marl on the south side of Mt. Alfeld; red and iridescent varieties at lo­calities in Desterus. A pale greenish blue variety is also found at the foot of Mt. Desterus. Two varieties are found at Goslar, one gray, the other whiter, the latter being used to make metal molds. Solid masses of these two varieties are split into thin sheets by the action of frost during the winter months. Two varieties are found between Gandersheim and Sesena, a town about five miles from the Harz forest. One is red, the other white, both being stony, tufaceous, and arenaceous. French and British farmers have used marl within our times. With either a rich, porous, or inter­mediate soil any farmer would profit greatly by using it since it would in­crease the fertility of his soil. The Ubii,1 according to Pliny, covered their fields with a foot of marl and then dug them up to a depth of three feet. This same method is used today by the inhabitants of Juliers and their neighbors. The material they use is rich although not as dense and hard as true marl. Pliny states that a poor soil can be improved by spreading a rich soil over it. Many believe this although it is foolish for the poor soil is not improved as has been proven in France and Britain. Only marl can improve the fertility of compact soil. Columella approved the practice of his uncle in using chalk on sandy soils when manure was not available.
I shall now consider the earths used by potters and sculptors. They, like the farmer, use unctuous earths but the farmer prefers porous earths while they prefer those which are dense and semi-soft, never as hard as marl. Both Theophrastus and Dioscorides write that some of the earths from Samos were suitable for their needs. If dense earths are not available the intermediate varieties are superior to the porous. Intermediate or semi-hard clays are the best, the soft, next. Porous clays are rarely used and those which are incoherent are valueless. When porous varieties are
1 An ancient German people who dwelt on the east bank of the Rhine near Cologne.
Book II About different applications of earths (painting, medical) and their occurrences Page of 251 Book II About different applications of earths (painting, medical) and their occurrences
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