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prevents the generation of marshy insects; it also soondestroys such as are passing from the higher level, by thesaltness of its water to which they are unaccustomed.An instance of this kind occurs in the Gallic marshesabout Altinum, Ravenna, and Aquileia, and other placesin Cisalpine Gaul, near marshes which, for the reasonsabove named, are remarkably healthy. When the marshesare stagnant, and have no drainage by means of riversor drains, as is the case with the Pontine marshes, theybecome putrid, and emit vapours of a heavy and pesti-lent 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 placedthat the inhabitants were continually out of health. Atlength they applied to Marcus Hostilius, and publiclypetitioned him, and obtained his consent, to be allowedto seek and select a more wholesome spot to which thecity might be removed. Without delay, and with muchjudgment, he bought an estate on a healthy spot close tothe sea, and requested the Roman senate and peopleto permit the removal of the city. He then set out thewalls, and assigned a portion of the soil to each citizen ata moderate valuation. After which, opening a communi-cation between the lake and the sea, he converted theformer into an excellent harbour for the city. Thus theSalapians now inhabit a healthy situation, four miles fromtheir ancient city.