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Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth

Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Page of 251 Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Text size:minus plus Restore normal size   Mail page  Print this page
BOOK X
219
All these earths have the dual nature of both an earth and the congealed juice contained in them. Nature has given these congealed juices a fiery force. Pure earths dry and cool, saline earths dry and are also moder­ately astringent and cleansing. Alkali earths are more cleansing; alumi­nous earths more astringent; atramentiferous earths strongly astringent and also mordacious; sulphurous and bituminous earths discutient; and earths containing the juice that has no name are acrid. Chrysocolla, aerugo caeruleum, realgar, and orpiment make an earth mordacious. Thus earths possess variable properties depending upon the congealed juice they contain.
There are as many different compound substances as there are species of earths. For example, if any of the congealed juices are added to ocher, red ocher, or another species of earth they will change the nature of the compound substance. Since I have discussed the species of earths in Book II, it will not be necessary to mention them here.
Sometimes the same earth may contain several congealed juices. When the powdered rock from Pozzuolo is used in building walls in the sea it is soon converted into an impregnable stone by the waves, according to Pliny.30 It contains alum, bitumen, and sulphur and is found on the hills of Pozzuolo in the Baiae district and, according to Vitruvius, in the fields of free towns near Mt. Vesuvius. According to Pliny a similar earth is found in the Cyzicena district where it is quarried in great masses and the earth itself, not a powder, placed in the sea where it is converted into stone. Similar earth is reported to occur near Cassandria. Oropus writes that any earth will be changed to stone if placed in the sea. These earths possess within themselves a quality which changes them into stones al­though waters may have this same quality as I have mentioned else­where. It is necessary that this species of earth be either aluminous, bitu­minous, or atramentiferous.
I shall now take up the earths that enclose stones and adhere to them. Samian earth sometimes contains samius lapis and chalk often contains silicious nodules. Very often small pebbles adhere to lumps of earth. Large masses of earth sometimes contain whole rocks, marbles, and stones, sometimes fragments of these, so it is to be expected that small lumps of earth would contain and surround pebbles of rock, marble, and stone as well as gravel, sand, and even gems. For this reason, when describing a locality we say that the earth or soil contains rocks, marble, or stones, or is full of pebbles or gravel, or it is sandy, or, in some cases, gem-bearing, or full of calcareous nodules. Since there are so many species of stones, gems, marbles, rocks, pebbles, gravel, and sand it is apparent that this genus of compound substances has a very great variety of compositions. For example, if hematite occurs in a mass of earth it will have a very
80 This is the pozzuolana rock that is used today in the manufacture of hydraulic cement.
Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Page of 251 Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth
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