Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
These alternating elevations and depressions of the surface lead to the formation of lakes in winter; and the exhalations proceeding in the heat of summer from the putrescent organic substances which they contain engender that noxious fever-laden atmosphere, which in ancient times tainted the district as it taints it at the present day. It is a mistake to suppose that these miasmata were first occasioned by the neglect of cultivation, which was the result of the misgovernment in the last century of the Republic and under the Papacy. Their cause lies rather in the want of natural outlets for the water; and it operates now as it operated thousands of years ago. It is true, however, that the malaria may to a certain extent be banished by thoroughness of tillage--a fact which has not yet received its full explanation, but may be partly accounted for by the circumstance that the working of the surface accelerates the drying up of the stagnant waters.
It must always remain a remarkable phenomenon, that a dense agricultural population should have arisen in regions where no healthy population can at present subsist, and where the traveller is unwilling to tarry even for a single night, such as the plain of Latium and the lowlands of Sybaris and Metapontum. We must bear in mind that man in a low stage of civilization has generally a quicker perception of what nature demands, and a greater readiness in conforming to her requirements; perhaps, also, a more elastic physical constitution, which accommodates itself more readily to the conditions of the soil where he dwells. In Sardinia agriculture is prosecuted under physical conditions precisely similar even at the present day; the pestilential atmosphere exists, but the peasant avoids its injurious effects by caution in reference to clothing, food, and the choice of his hours of labour. In fact, nothing is so certain a protection against the "aria cattiva" as wearing the fleece of animals and keeping a blazing fire; which explains why the Roman countryman went constantly clothed in heavy woollen stuffs, and never allowed the fire on his hearth to be extinguished. In other respects the district must have appeared attractive to an immigrant agricultural people: the soil is easily laboured with mattock and hoe and is productive even without being manured, although, tried by an Italian standard, it does not yield any extraordinary return: wheat yields on an average about five-fold.(3) Good water is not abundant; the higher and more sacred on that account was the esteem in which every fresh spring was held by the inhabitants.
3. A French statist, Dureau de la Malle (-Econ. Pol. des Romains-, ii. 226), compares with the Roman Campagna the district of Limagne in Auvergne, which is likewise a wide, much intersected, and uneven plain, with a superficial soil of decomposed lava and ashes--the remains of extinct volcanoes. The population, at least 2500 to the square league, is one of the densest to be found in purely agricultural districts: property is subdivided to an extraordinary extent. Tillage is carried on almost entirely by manual labour, with spade, hoe, or mattock; only in exceptional cases a light plough is substituted drawn by two cows, the wife of the peasant not unfrequently taking the place of one of them in the yoke. The team serves at once to furnish milk and to till the land. They have two harvests in the year, corn and vegetables; there is no fallow. The average yearly rent for an arpent of arable land is 100 francs. If instead Of such an arrangement this same land were to be divided among six or seven large landholders, and a system of management by stewards and day labourers were to supersede the husbandry of the small proprietors, in a hundred years the Limagne would doubtless be as waste, forsaken, and miserable as the Campagna di Roma is at the present day.
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Reference address : https://www.ellopos.net/elpenor/rome/1-03-settlements-latins.asp?pg=6