All salt is either native or artificial;3106 both kinds being formed in various ways, but produced from one of these two causes, the condensation or the desiccation, of a liquid.3107 The Lake of Tarentum is dried up by the heat of the summer sun, and the whole of its waters, which are at no time very deep, not higher than the knee in fact, are changed into one mass of salt. The same, too, with a lake in Sicily, Cocanicus by name, and another in the vicinity of Gela. But in the case of these two last, it is only the sides3108 that are thus dried up; whereas in Phrygia, in Cappadocia, and at Aspendus, where the same phænomena are observable, the water is dried up to a much larger extent, to the very middle of the lake, in fact. There is also another marvellous3109 circumstance connected with this last—however much salt is taken out of it in the day, its place is supplied again during the night. Every kind of lake-salt is found in grains, and not in the form of blocks.3110

Sea-water, again, spontaneously produces another kind of salt, from the foam which it leaves on shore at high-water mark, or adhering to rocks; this being, in all cases, condensed by the action of the sun, and that3111 salt being the most pungent of the two which is found upon the rocks.

There are also three different kinds of native salt. In Bactriana there are two vast lakes;3112 one of them situate on the side of Scythia, the other on that of Ariana, both of which throw up vast quantities of salt.3113 So, too, at Citium, in Cyprus; and, in the vicinity of Memphis, they extract salt from the lake and dry it in the sun. The surface-waters of some rivers, also, condense3114 in the form of salt, the rest of the stream flowing beneath, as though under a crust of ice; such as the running waters near the Caspian Gates3115 for instance, which are known as the “Rivers of Salt.” The same is the case, too, in the vicinity of the Mardi and of the people of Armenia. In Bactriana, also, the rivers Ochus3116 and Oxus carry down from the mountains on their banks, fragments of salt. There are also in Africa some lakes, the waters of which are turbid, that are productive of salt. Some hot springs, too, produce salt—those at Pagasæ for example. Such, then, are the various kinds of salt produced spontaneously by water.

There are certain mountains, also, formed of native salt; that of Oromenus, in India, for example, where it is cut out like blocks from a quarry, and is continually reproduced, bringing in a larger revenue to the sovereigns of those countries than that arising from their gold and pearls. In some instances it is dug out of the earth, being formed there, evidently, by the condensation of the moisture, as in Cappadocia for example, where it is cut in sheets, like those of mirror-stone.3117 The blocks of it are very heavy, the name commonly given to them being “mica.”3118 At Gerrhæ,3119 a city of Arabia, the ramparts and houses are constructed of blocks of salt, which are soldered together by being moistened with water. King Ptolemæus discovered salt also in the vicinity of Pelusium, when he encamped there; a circumstance which induced other persons to seek and discover it in the scorched tracts that lie between Egypt and Arabia, beneath the sand. In the same manner, too, it has been found in the thirsting deserts of Africa, as far as the oracle of Hammon,3120 a locality in which the salt increases at night with the increase of the moon.

The districts of Cyrenaica are ennobled, too, by the production of hammoniacum,3121 a salt so called from the fact of its being found beneath the sands3122 there. It is similar in colour to the alum known as “schiston,”3123 and consists of long pieces, by no means transparent, and of an unpleasant flavour, but highly useful in medicine; that being held in the highest esteem, which is the clearest and divides into straight3124 flakes. There is one remarkable fact mentioned in connexion with it: so long as it lies under ground in its bed3125 it is extremely light, but the moment it is exposed to the light, it is hardly credible to what an extent its weight is increased. The reason for this is evident:3126 the humid vapours of the excavations bear the masses upwards, as water does, and so aid the workmen. It is adulterated with the Sicilian salt which we have mentioned as being found in Lake Cocanicus, as also with that of Cyprus, which is marvellously like it. At Egelasta,3127 in Nearer Spain, there is a salt, hewn from the bed in almost transparent blocks, and to which for this long time past most medical men, it is said, have given the preference over all other salt. Every spot in which salt3128 is found is naturally barren, and produces nothing. Such are the particulars, in general, which have been ascertained with reference to native salt.

Of artificial salt there are several kinds; the common salt, and the most abundant, being made from sea-water drained into salt-pans, and accompanied with streams of fresh water; but it is rain more particularly, and, above all things, the sun, that aids in its formation; indeed without this last it would never dry. In the neighbourhood of Utica, in Africa, they build up masses of salt, like hills in appearance; and when these have been hardened by the action of the sun and moon, no moisture will ever melt them, and iron can hardly divide them. In Crete, however, salt is made without the aid of fresh water, and merely by introducing sea-water into the salt-pans. On the shores of Egypt, salt is formed by the overflow of the sea upon the land, already prepared for its reception, in my opinion, by the emanations of the river Nilus. It is made here, also, from the water3129 of certain wells, discharged into salt-pans. At Babylon, the result of the first condensation is a bituminous3130 liquid, like oil, which is used for burning in lamps; when this is skimmed off, the salt is found beneath. In Cappadocia, also, both well and spring-water are introduced into the salt-pans. In Chaonia there is a spring, from the water of which, when boiled3131 and left to cool, there is an inert salt obtained, not so white as ordinary salt. In the Gallic provinces and in Germany, it is the practice to pour salt-water upon burning wood.3132