The soil itself, too, gives indications of the presence of water, by presenting white spots, or an uniformly green appearance: for where the stratum is black the springs are mostly not of a permanent nature. The presence of potter's clay always puts an end to all hopes of finding water, and the excavation is immediately abandoned; an eye being carefully kept to the strata[1] of the earth, to see whether, beginning with black mould, it successively presents the appearances above-mentioned. The water is always fresh that is found in argillaceous soils, but in a stratum of tufa it is colder than elsewhere; this, indeed, being a soil which is highly approved of, as having a tendency to make the water pure and extremely light to the stomach, and, by its action as a filter, to withhold all impurities. The presence of sand[2] gives indications of springs of but limited extent, and of water impregnated with slime; while that of gravel announces the presence of water of excellent flavour, but not to be depended upon for permanence. Male:[3] sand, fine sea[4]-sand, and charcoal[5] earth, yield a constant supply of water of a highly wholesome quality; but it is the presence of red stones that is the most to be depended upon, and the water found there is of the very finest quality. Craggy localities at the foot of mountains, and silicious soils, are equally good; in addition to which, the water found there is cooler than elsewhere.

In boring for water, the soil should always become more and more humid, and, the deeper the descent, with the greater facility the implements should penetrate. In deep-sunk wells, the presence of sulphureous[6] or aluminous substances is fatal to the sinkers; a danger that may be guarded against by letting down a lighted lamp, and ascertaining whether the flame is extinguished. When such is found to be the case, it is the practice to sink vent-holes on each side of the well, both right and left, in order to receive and carry off the noxious exhalations. Independently of these evils, the air becomes heavier, from the great depth merely of the excavation, an inconvenience which is remedied by keeping up a continual circulation with ventilators of linen cloth. As soon as water is reached, walls are constructed at the bottom, but without cement,[7] in order that the springs may not be intercepted.

Some waters, the sources of which do not lie on elevated ground, are coldest at the beginning of spring, being maintained by the winter rains in fact. Others, again, are coldest at the rising of the Dog-star—peculiarities, both of them, to be witnessed at Pella in Macedonia; for in front of that city there is a marsh-spring, which at the beginning of summer is cold, while in the more elevated parts of the city the water is ice-cold[8] in the hottest days of summer. The same is the case, too, at Chios, the water-supply of the harbour and of the city occupying the same relative positions. At Athens, the water of the Fountain Enneacrunos[9] is colder in a cloudy summer than the well there in the garden of Jupiter; while on the other hand, this last is ice-cold during the drought of a hot summer. For the most part, however, wells are coldest about the rising of Arcturus.[10]

(4.) The water-supply of wells never fails in summer, but in all cases it falls low during four days at the rising of the constellation above-mentioned. Throughout the whole winter, on the other hand, many wells entirely fail; as in the neighbourhood of Olynthus, for example, where the water returns in the early days of spring. In Sicily too, in the vicinity of Messana and Mylæ, the springs are entirely dry throughout the winter, while in summer they overflow and form quite a river. At Apollonia in Pontus there is to be seen, near the sea-shore, a fountain which overflows in summer only, and mostly about the rising of the Dog-star; should the summer, however, not be so hot as usual, its water is less abundant. Certain soils become drier in consequence of rain, that in the territory of Narnia for example: a fact which M. Cicero has mentioned in his "Admiranda," with a statement that drought is there productive of mud, and rain of dust.[11]