Insaluhrilif of the Air of the Maremma. 235 



moisture, &c. ; for other localities, very unfavourably circum- 

 stanced in these respects, are not subject to the same morbid 

 influences. 



He notices another opinion existing in Tuscany, which, 

 though absurd at first sight, appears to him not to be desti- 

 tute of some foundation. It is stated, that these lands, after 

 having been dried by the heat of the summer, and then sub- 

 jected to rain water, undei'go a kind of fermentation ; that the 

 earth hails {ribolle), as they commonly say ; and that, in conse- 

 quence of this ebullition, deleterious miasmata are disengaged, 

 which are the source of diseases, and particularly of intermit- 

 tent fevers. It is quite certain that diseases do not commence, 

 or at least do not become common, until after rain and inun- 

 dations have occurred. The greater the alternations of heat 

 and rain which occur in a year, the more are the ravages of 

 fever felt. This is a fact ascertained by experience, and which 

 no inhabitant of the maremma would deny. It is cited by many 

 authors, especially by the celebrated Brocchi*. 



It is also asserted, that these circumstances are productive 

 of fevers, not only in marshy soils, but also in certain situa- 

 tions that contain no marshes, such as that of the environs of 

 Volterra. Instead therefore of saying, as often happens, that 

 the morbid effects are derived from a mixture of rain and stag- 

 nant water, it would be more rational to say that they are due 

 to the action of water on certain parched lands. 



Examination of the Substratum of unhealthy Marshes. 

 M. Savi begins by observing, that all marshes do not appear 

 to be capable of evolving hurtful effluvia ; hence the necessary 

 distinction between unhealthy and indifferent marshes. It is, 

 ho\vever, well known that the latter contain scarcely any salts 

 in solution, and the substratum yields no marine mineral pro- 

 ducts. Such is the marsh of Bientina, and also that of Ma- 

 ciuccoli. The unhealthy marshes are those which hold in 

 solution a notable proportion of salts, and they may be divided 

 into three classes, according to the source of the salts : — 

 1. those of mineral waters (lake of Rimigliano, &c.) ; 2. those 

 of sea water ; 3. those of land formerly occupied by sea water 

 (marshes of Castiglion della Pescaja, of Scarlino, &c.). In 

 the Tuscan maremma the unhealthy marshes belong to the 

 two latter classes. They are for the most part small ancient 

 gulfs, at first changed into low lands by the alluvium of rivers, 

 and then more or less separated from the sea by an accumu- 

 lation of sand heaped up by the action of the winds and 

 waves. 



* Da C Elal I'lj^siqac du Sul Roman, page 27G. 



