Only the central portion of that region between the Tiber, the spurs of the Apennines, the Alban Mount, and the sea--a district of about 700 square miles, not much larger than the present canton of Zurich--was Latium proper, the "plain,"(2) as it appears to the eye of the observer from the heights of Monte Cavo.

Though the country is a plain, it is not monotonously flat.
With the exception of the sea-beach which is sandy and formed in part by the accumulations of the Tiber, the level is everywhere broken by hills of tufa moderate in height though often somewhat steep, and by deep fissures of the ground.

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.