Page:Vitruvius the Ten Books on Architecture.djvu/267

229 and all conducted by means of subterranean channels into one place.

The mountains and districts with a northern exposure are the best spots in which to search, for the reason that springs are sweeter, more wholesome, and more abundant when found there. Such places face away from the sun's course, and the trees are thick in them, and the mountains, being themselves full of woods, cast shadows of their own, preventing the rays of the sun from striking uninterruptedly upon the ground and drying up the moisture.

7. The valleys among the mountains receive the rains most abundantly, and on account of the thick woods the snow is kept in them longer by the shade of the trees and mountains. Afterwards, on melting, it filters through the fissures in the ground, and thus reaches the very foot of the mountains, from which gushing springs come belching out.

But in flat countries, on the contrary, a good supply cannot be had. For however great it is, it cannot be wholesome, because, as there is no shade in the way, the intense force of the sun draws up and carries off the moisture from the flat plains with its heat, and if any water shows itself there, the lightest and purest and the delicately wholesome part of it is summoned away by the air, and dispersed to the skies, while the heaviest and the hard and un­pleasant parts are left in springs that are in flat places.

1. has, therefore, more wholesome qualities, be­cause it is drawn from the lightest and most delicately pure parts of all the springs, and then, after being filtered through the agi­tated air, it is liquefied by storms and so returns to the earth. And rainfall is not abundant in the plains, but rather on the moun­tains or close to mountains, for the reason that the vapour which