Insalubrity of the Air of the Maremma. 239 



Can Sulphuretted and Carhuretted Hydrogen either directly or 

 indirectly render the Air insalubrious ? 



The insalubrity of the air has lieen long attributed to these 

 gases; this observation has been questioned with respect to 

 sulphuretted hydrogen by many philosophers, who observed 

 that the emanations of the solfatcrras and lagoni of the Siennois 

 and Volterrano, which contain a considerable ^iroportion of this 

 gas, do not occasion the marsh diseases in those who breathe 

 the air of these localities. The same observation applies to 

 the air of the lagoons of Venice. These incontestable facts 

 prove that sulphuretted hydrogen is not always capable of 

 producing fevers; but as in all the localities of marshes in 

 which unwholesome air prevails, sulphuretted or carburetted 

 hydrogen, and especially the former, are generated, their for- 

 mation is naturally regarded as connected, at least, with the 

 cause of insalubrity. 



The author will not however affirm that insalubrity depends 

 on one cause only : several circumstances may concur to de- 

 velop noxjous influences, or much to increase their malignity- 

 Such is the effect already attributed by several philosophers 

 to winds from the south, and the sirocco, which, stemmed by 

 the chain of the Apennines, appear greatly to increase insalu- 

 brity, whilst the winds from the north produce favourable 

 effects on unhealthy countries. 



Conclusions. 



It appears to be proved that places exposed to the effects 

 of insalubrious air are- — 



1st. Lands containing collections of stagnant and salt water, 

 or lands which are not submerged, but which contain saline 

 matters and organic substances, when watered by the rains of 

 summer. 



2nd. Lands receiving mineral waters containing sulphates 

 and chlorides, which rest upon decomposing organic matter. 



3rdly. Shores on which masses of algae accumulate, which 

 are afterwards watered by fresh water, or by a mixture of iVesh 

 and salt water. 



As an hypothesis resulting from the facts observed, the au- 

 thor particularizes sulphuretted and carburetted hydrogen 

 gases, if not as the direct agents of deleterious infltuence, yet 

 as contributing to the production of malaria. In a word, the 

 origin of the insalubrious air is associated with the production 

 of these hydroj^uretted gases. 



