BOOK III	37
	between there and Arabia, in Cyrenaica. While all this latter salt can be called sal ammoniac, the name is usually given only to that from Cyre­naica. So much regarding the occurrence of natural halite within the earth. Natural halite is found also in springs, rivers, lakes and oceans on the surface of the earth. Springs, such as the hot springs at Pegasius, may carry salt. It is often produced from rivers when they are dried up by the sun's heat. The salt plain of Narbonne, France, is of this origin. The plain near the marshy spring at Schonbach in Elboganum becomes white with salt during the summer. A river may carry small grains of salt as do the Oxus and Ochus rivers where they flow out of the mountains opposite Balkh, or rivers may have a crust of salt on the surface and the water will flow out from under this crust as freely as does the water from under a glacier. An example of the latter is the river which flows into the Caspian Sea between Armenia and Mardos. Pliny has written extensively about salt, apparently having taken it from Theophrastus. A lake may be sat­urated with salt and even turn into solid salt. It turns into salt in dif­ferent ways. The entire lake may be so converted as at Taranto, Apulia, and at Tragasaeus, Aeolia, which is near Amaxitus not far from the temple of Apollo. One part of the lake may turn to salt as at Tuz Geul, Phrygia, from whence comes the Tattaeus salt; in Cappadocia; at Aspendus, Pam-phylia. Only the ends of some lakes are converted into salt as at Cocanicus and Gela, Sicily. The lake near Citium, Cyprus, and the Dead Sea of Palestine have become saturated with salt. The salt from the Dead Sea is called "Salt of Sodom." Other lakes that produce salt are two desolate lakes in Balkh, one near Scythia, the other near Arios; one near Memphis, Egypt; many in Africa. Salt forms in thin crusts on the shores of oceans. In summer when it is hot foam forms and this is driven onto the shore and rocks. This foam, cut off from the ocean, dries and is converted into salt. The material Dioscorides calls a\os άχνης, Pliny calls "foam" and we, usually, "dry sea foam" or more correctly "salt formed from sea foam." Younger writers call it salts spuma (foam of salt). Although they write in this poetic manner nevertheless they understood its origin as I shall explain elsewhere. I have said enough about the origin of halite and shall now take up briefly the manufacture of salt since I can explain the differences in its natural properties and formation more accurately this way. Salt is pro­duced from marine waters, saline springs, salt wells, and from alkaline solutions. I shall explain the methods of making salt in a book on mining. Halite varies in color. The natural mineral from Sarmatia is transparent and white. Similar material is found in the Carpathians and in Dacia while the mineral from the lakes near Taranto is the finest of all. Our salt works at Luneburg produce white salt. "Flowers of salt" whether it blossoms in mines or brine pits is usually white. Gray halite is often not transparent, as at Sarmatia and Dacia. In these various localities the halite may be white in one place and black or gray in another. Norwegian salt which is