Natural History. 403 



by the old diseases. It appears, from the registers, that in these 

 two years, Viareggio had 170 deaths in a population of 1330, 

 making nearly 1 in 15 for each year, whilst in the year follow- 

 ing, the deaths were 32, or 1 in 40. The cause was found to exist 

 in the damaged state of the gates in those two years, which per- 

 mitted the passage of the sea; they were repaired, and the evil 

 disappeared. 



A similar circumstance happened in the years 1784 and 1785; 

 in the first year, the deaths were 92 out of 1898 inhabitants, or 

 1 in 20 ; and in 1785, they were, 103 in 1834 inhabitants, or 1 in 

 18. The government reports state, that in this population of 

 1898, there were 1200 sick persons. The epidemic was stopped, 

 in 1769, by repairing the gates. 



Notwithstanding the success of the precautions taken at thig 

 part of the coast, the neighbouring parts were long left a prey to 

 the destroying influence of the mixed marsh-waters ; and the 

 inhabitants around the basins of Montrone and Perrotto were not 

 considered until the year 1804. In the years 1809, 1810, 1811, 

 similar means were taken with the best effects to the inhabitants 

 of Montignosini, and the vicinity, and in 1812, a sluice was con- 

 structed on the Cinquale, which perfected the arrangements in 

 this part, and made a large portion of country equally healthy 

 with Viareggio. To complete the arrangement, it was now only 

 required to guard the ditches of Montrone and Tonfala with 

 sluices ; the former was finished in 1819, and the latter in 1821. 



Since that time the diseases of mal-aria have ceased so entirely 

 at all points, that no other dangers are now incurred, regarding 

 the insalubrity of the atmosphere, than such as may arise from 

 neglect of these sluices, which the inhabitants of the country 

 should regard as their palladium. 



Now that it has been well ascertained that the exclusion of 

 the sea from the marshes ensures salubrity and vice versd, a vast 

 field is opened to researches, which, though difficult, delicate, and 

 expensive, are of the highest importance and utility. The follow- 

 ing are three points put by the author : — 



1. Is the developement of the pestilential miasmata due to the 

 mere mixture of soft and sea water, or is it occasioned by the 

 destruction of vegetable and animal species in the marshes by the 

 introduction of the latter ? 



2. In the one or other case, what are the chemical changes 

 effected by the mixture, the nature of the deleterious emanations, 

 the degree of heat requisite for their production, the influence of 

 the sun, and the mud of the marsh, #c. fyc.? 



3. What was their action on the animal system ? To what 

 distance may they extend ? and in general, by what circumstances 

 are they modified ? #c. — Ann. de Chim. xxix. 225. 



