4 20 THE POPULAR SCIENCE MONTHLY. 



Renewed in 1730 by Manfredi, and six years later by Zendrini, a mathe- 

 matician of Bologna, the idea was finally carried into execution in 

 1740. The initial attempt was made upon the principal and most un- 

 healthful 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 open- 

 ing 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 Viar- 

 regio, 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 aris- 

 tocracy 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 l768-'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 oc- 

 curred 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 con- 

 ceived the great idea of improving the whole Tuscan Maremma in 

 the same manner. It was an immense undertaking which he contem- 

 plated 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 ex- 

 poses 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. 



