Amongst the changes effected by human agency in the basin of the Arno those referring to the Val di Chiana are, perhaps, the most important. This depression connects the basins of the Arno and Tiber, and may possibly have served as an outlet to the former river before it had opened itself a way through the {244} gorge below Florence. Formerly the water-parting between the two rivers was close to the Arno. A small portion of its drainage was carried to the Tuscan river, but by far the greater portion of the vale was occupied by stagnant pools, extending to the south as far as the latitude of Montepulciano, a distance of twenty miles. The whole of this region was a breeding-place of fever. Dante and other Italian writers speak of it as an accursed place. The inhabitants made vain attempts at drainage. The illustrious Galileo, when consulted on the subject, {245} declared that nothing could be done to mend this evil; and though Torricelli conceived that it would be possible to drain the valley, he took no steps to put his theories into practice.

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Fig. 86.—THE LAKE OF BIENTINA.

From the Austrian Staff Map. Scale 1 : 328,000.

About the middle of the eighteenth century the work of drainage was at length seriously taken in hand, directed by Fossombroni, the celebrated engineer. “Warps,” or colmate, were thrown up at the outlet of each lateral ravine between which the débris carried down from the flanks of the mountains was deposited. The swamps gradually filled up, and the soil became firm. By constructing a dam (argine) across the vale at the point chosen for the new water-parting, an outfall was created, and a line of stagnant swamps was thus converted into a pure rivulet. The valley, at one time a hotbed of fever, has now become one of the most salubrious districts of Italy. The newly won lands were at once taken possession of by agriculturists, and 500 square miles were thus added to the productive area of Tuscany. Villages, formerly inhabited by fever-stricken wretches, have become wealthy towns, and the success of this bonification, or reclamation, has been thorough. The torrents are under control now, and have already deposited 17,650 million cubic feet of alluvium over an area of 50,000 acres, as if they were intelligent workmen. The same system of drainage has been successfully applied in other parts of Italy, and particularly near Grosseto, on the right bank of the Ombrone.

Amongst the great drainage works which will evermore contribute to the glory of Tuscan engineers, the innumerable canals draining the plains of Fucecchio, {246} Pontedera, Pisa, Lucca, Leghorn, and Viareggio, each of which was formerly occupied by its lake, deserve to be noticed. One of the most difficult of these lakes is that of Bientina, or Sesto, to the east of the Pisan hills, which is supposed to have been formed by an overflow of the Serchio. In former times this lake had two effluents, one running north to the Serchio, the other south to the Arno. The outfall left nothing to be desired in ordinary times, but after heavy rains the two effluents were converted into inflowing rivers, and if the sluices had not been closed, the Arno and the Serchio would have rejoined each other in this inland sea. The Bientina, during such freshets, covered six times its ordinary area, and in order to save the fertile fields of Tuscany it became absolutely necessary to create a third effluent. The engineers conceived the happy idea of conveying this new effluent through a tunnel, passing beneath the Arno, three feet in width, into an ancient bed of that river, now supplanted by the Colombrone.

In most of these enterprises it was necessary to struggle on in spite of the miasmatic atmosphere, which hung more particularly over the littoral zone, where the fresh inland water mingles with the salt water of the Me­di­ter­ra­nean. The blending of the two waters destroyed the fresh-water plants and animals, and the deleterious gases arising from their decomposition poisoned the atmosphere. About the middle of last century an engineer, Zendrini, proposed to construct sluices separating the fresh from the salt water. This was done, and the fevers at once disappeared. In 1768, the sluices having been allowed to fall out of repair, the miasmatic scourge immediately reappeared, and it was not until they had been repaired that the sanitary condition of the villages along the coast was improved. Twice since neglect to keep the sluices in a proper condition has been punished with the same results; but from 1821 they have been maintained in thorough order, and the sanitary condition of the country has ever since been most satisfactory. Viareggio, in the centre of this malarial district, was up to 1740 hardly more than a hamlet, avoided on account of its insalubrity, but is now a seaside town, the favourite resort of numbers of visitors.

Much has been done, no doubt, in draining the land, but there is still room for many improvements. The Maremma, a track between Piombino and Orbetello, remains one of the most insalubrious regions of Europe, in spite of what has been done by sanitary engineers. The inhabitants never reach a high age, and though they descend to the plain only when it is absolutely required for cultivating their fields, they frequently carry away with them the germs of disease. In the two summers of 1840 and 1841 no less than 36,000 persons suffered from fever amongst a total population of 80,000 souls, most of whom reside in villages built on hills, and only rarely visit the pestilential plain. In order to escape the pernicious influence of the poisonous air, it is necessary to reside constantly at an elevation of 325 feet above the sea, and even that does not always suffice, for the episcopal city of Sovana is notoriously unhealthy, though built at that height. Fevers occur frequently at a distance from the swamps, and Salvagnoli Marchetti is of opinion that they are due to the nature of the soil. The malaria is said to creep up clayey hills permeated by empyreumatic substances; it likewise {247} poisons the air of districts abounding in saline springs, and still more that near deposits of alum. Southerly winds are likewise most pernicious, and fevers rise highest in the valleys which are exposed to them. Places, on the other hand, which are fully open to the sea breeze are quite free from malaria, even if swamps are near, as at Orbetello and Piombino.

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