Renewed in 1730 by Manfredi, and six years later by Zendrini, a mathematician of Bologna, the idea was finally carried into execution in 1740. The initial attempt was made upon the principal and most unhealthful basin. A sluice was constructed at the entrance of the canal of Burlamacca through which the waters of the sea penetrated into the basin to its central pond. The flood-gate was so arranged as to act like a valve, shutting by the pressure of the rising tide and opening when it fell. The success of this enterprise was so complete that in the following year the miasmatic diseases which had never failed to show themselves annually did not reappear, and the whole district was rendered salubrious. It was at this period that the village of Viarregio, previously abandoned and composed only of a few fishers' huts grouped at the foot of an old tower where galley-slaves were confined, became a place of fashionable resort during the summer for the aristocracy of Lucca. This fact of a region's being rendered healthy by the exclusion of sea-water is curious, but made more decisive still by its counter-proof. In 1768−'69 fevers suddenly sprang up again as bad as ever in the same territory. Upon the cause being investigated, it was found that the sluice had become deranged and the mixture of waters had been reestablished. Upon the flood-gate being repaired, the malaria was again extinguished. The same occurrence happened in 1784−'85. The sluice having been neglected, there took place in 1784, out of a population of 1,900, the enormous number of 1,200 cases of malarial fever and 92 deaths. In the following year there occurred 103 deaths. The trouble was remedied in the same manner as before. The other portions of the Maremma were rendered healthy later, by sluices successively established at different points. Such a remarkable result necessarily attracted public attention. Leopold II., Grand-duke of Tuscany, was particularly impressed by it, and he conceived the great idea of improving the whole Tuscan Maremma in the same manner. It was an immense undertaking which he contemplated—an actual transformation of a large part of his dominions—and it redounds to his glory that he succeeded, in the face of almost insurmountable obstacles, by the means described, and a properly-directed system of canalization and field-culture, in regenerating a very considerable portion of his territory.
It is not difficult to account for the generation of malaria under such circumstances as those just mentioned. The minute forms of vegetable life with which both fresh and salt water teem require their own special element for continued existence. The intermixture of salt with fresh water introduces a new element with which the life maintained in each separately is incompatible. The surface of the soil consequently after every invasion and retirement of the tide exposes to the action of the heat a mass of defunct vegetable material spread out over an extensive area, and in most favorable condition for speedy decomposition.