‹‹‹ Vitr. 5.9.5 | Table of Contents | Vitr. 5.9.7 ›››
6That this is the case, may be proved by observing, that from fountains in covered places, or those which are under ground, no moist vapours rise; whilst in open places exposed to the air, when the rising sun darts his rays upon the earth, he raises the vapours from humid and marshy places, and, gathering them into masses, carries them into the air. If, therefore, in open places, the noxious humours of bodies are carried off by the air, as they are from the earth by means of clouds, there can be no doubt of the necessity of making spacious and pleasant walks open to the air in every city.
6That this is so may be seen from the fact that misty vapours never arise from springs of water which are under cover, nor even from watery marshes which are underground; but in uncovered places which are open to the sky, when the rising sun begins to act upon the world with its heat, it brings out the vapour from damp and watery spots, and rolls it in masses upwards. Therefore, if it appears that in places open to the sky the more noxious humours are sucked out of the body by the air, as they obviously are from the earth in the form of mists, I think there is no doubt that cities should be provided with the roomiest and most ornamented walks, laid out under the free and open sky.