4In setting out the walls of a city the choice of a healthy situation is of the first importance: it should be on high ground, neither subject to fogs nor rains; its aspects should be neither violently hot nor intensely cold, but temperate in both respects. The neighbourhood of a marshy place must be avoided; for in such a site the morning air, uniting with the fogs that rise in the neighbourhood, will reach the city with the rising sun; and these fogs and mists, charged with the exhalation of the fenny animals, will diffuse an unwholesome effluvia over the bodies of the inhabitants, and render the place pestilent. A city on the sea side, exposed to the south or west, will be insalubrious; for in summer mornings, a city thus placed would be hot, at noon it would be scorched. A city, also, with a western aspect, would even at sunrise be warm, at noon hot, and in the evening of a burning temperature.
2Hence the constitutions of the inhabitants of such places, from such continual and excessive changes of the air, would be much vitiated. This effect is likewise produced on inanimate bodies: nobody would think of lighting his wine-cellar from the south or the west, but from the north, an aspect not liable to these violent changes. In granaries whose aspects are south of the east or west, the stores are soon ruined; and provisions, as well as fruits, cannot be long preserved unless kept in apartments whose aspects are north of the east or west.
3For heat, which acts as an alterative, by drying up the natural moisture of any body, destroys and rots those substances on which it acts. Iron, for instance, naturally of a hard texture, becomes so soft when heated in a forge as to be easily wrought into any form; but if, when heated, it is suddenly immersed in cold water, it immediately regains its original quality.
4Thus, not only in unwholesome, but also in salubrious districts, the summer heats produce languor and relaxation of body; and in winter, even the most pestilential situations become wholesome, inasmuch as the cold strengthens and restores the constitution of the inhabitants. Hence, those who change a cold for a hot climate, rarely escape sickness, but are soon carried off; whereas, on the other hand, those who pass from a hot to a cold climate, far from being injured by the change, are thereby generally strengthened.
5Much care, then, should be taken so to set out the walls of a city, that it may not be obnoxious to the pestilential blasts of the hot winds. For as, according to those principles which the Greeks call στοιχεῖα, all bodies are compounded of fire, water, earth, and air, by whose union and varying proportions the different qualities of animals are engendered;
6so, in those bodies wherein fire predominates, their temperament is destroyed, and their strength dissipated. Such is the case in exposure to certain aspects of the heavens whence the heat insinuates itself through the pores in a greater degree than the temperature of the system will bear. Bodies which contain a greater proportion of water than is necessary to balance the other elements, are speedily corrupted, and lose their virtues and properties. Hence bodies are much injured by damp winds and atmosphere. Lastly, the elements of earth and air being increased or diminished more than is consistent with the temperature of any given body, will have a tendency to destroy its equilibrium; the earthy elements by repletion, the aërial by the weight of the atmosphere.
7If any one doubt this, let him study the different natures of birds, fishes, and animals of the land, and he will easily perceive the truth of these principles, from the variety existing among them. For there is one flesh of birds, another of fishes, and another, very different, of land animals. Birds have a small proportion of earth and water in their nature, a moderate quantity of heat, and a considerable portion of air; whence, being light by nature, from their component elements, they more easily raise themselves in the air. Fishes, by nature adapted to the watery element, are compounded of but a moderate degree of heat, a considerable proportion of air and earth, and a very small portion of water, the element in which they live; and hence, easier exist in it. Wherefore, when removed from it, they soon die. Terrestrial animals, being constituted with much air, heat, and water, and but little earth, cannot live in the water, on account of the quantity of that element naturally preponderating in their composition.
8Since, then, we are thus constantly reminded, by our senses, that the bodies of animals are so constituted, and we have mentioned that they suffer and die from the want or superabundance of any one element not suitable to their temperament, surely much circumspection should be used in the choice of a temperate and healthy site for a city.
9The precepts of the ancients, in this respect, should be ever observed. They always, after sacrifice, carefully inspected the livers of those animals fed on that spot whereon the city was to be built, or whereon a stative encampment was intended. If the livers were diseased and livid, they tried others, in order to ascertain whether accident or disease was the cause of the imperfection; but if the greater part of the experiments proved, by the sound and healthy appearance of the livers, that the water and food of the spot were wholesome, they selected it for the garrison. If the reverse, they inferred, as in the case of cattle, so in that of the human body, the water and food of such a place would become pestiferous; and they therefore abandoned it, in search of another, valuing health above all other considerations.
10That the salubrity of a tract of land is discovered by the pastures or food which it furnishes, is sufficiently clear, from certain qualities of the lands in Crete, situate in the vicinity of the river Pothereus, which lie between the two states of Gnosus and Gortyna. There are pasturages on each side of this river: the cattle, however, pastured on the Gnossian side, when opened, are found with their spleens perfect; whilst those on the opposite side, nearer to Gortyna, retain no appearance of a spleen. Physicians, in their endeavours to account for this singular circumstance, discovered a species of herb eaten by the cattle, whose property was that of diminishing the spleen. Hence arose the use of the herb which the Cretans call ἄσπληνος, as a cure for those affected with enlarged spleen.
11When, therefore, a city is built in a marshy situation near the sea-coast, with a northern, north-eastern, or eastern aspect, on a marsh whose level is higher than the shore of the sea, the site is not altogether improper; for by means of sewers the waters may be discharged into the sea: and at those times, when violently agitated by storms, the sea swells and runs up the sewers, it mixes with the water of the marsh, and prevents the generation of marshy insects; it also soon destroys such as are passing from the higher level, by the saltness of its water to which they are unaccustomed. An instance of this kind occurs in the Gallic marshes about Altinum, Ravenna, and Aquileia, and other places in Cisalpine Gaul, near marshes which, for the reasons above named, are remarkably healthy.
12When the marshes are stagnant, and have no drainage by means of rivers or drains, as is the case with the Pontine marshes, they become putrid, and emit vapours of a heavy and pestilent nature. Thus the old city of Salapia, in Apulia, built, as some say, by Diomedes on his return from Troy, or, as others write, by Elphias the Rhodian, was so placed that the inhabitants were continually out of health. At length they applied to Marcus Hostilius, and publicly petitioned him, and obtained his consent, to be allowed to seek and select a more wholesome spot to which the city might be removed. Without delay, and with much judgment, he bought an estate on a healthy spot close to the sea, and requested the Roman senate and people to permit the removal of the city. He then set out the walls, and assigned a portion of the soil to each citizen at a moderate valuation. After which, opening a communication between the lake and the sea, he converted the former into an excellent harbour for the city. Thus the Salapians now inhabit a healthy situation, four miles from their ancient city.