On Tropical Miasmata. 29 
pieces of iron pyrites, surrounding different vegetable matters, 
as pieces of wood, stalks of plants, &e., have been found. 
This iron pyrites was partly crystallized, and, like the com- 
mon ore, so hard as to scratch glass. According to my ana- 
lysis, the composition of this iron pyrites agreed as nearly as 
possible with that examined by Berzelius. It is beyond a 
doubt that this sulphuret has been formed by the action of 
the vegetable matter contained in it, upon the sulphate of soda 
and the carbonate of protoxide of iron contained in the mi- 
neral water. It may be added that traces of the former only 
were present in it, whereby it may be shewn that even the 
smallest proportions of sulphates are sufficient to produce sul- 
phuretted hydrogen under the circumstances alluded to. 
“Besides the paper published by Signor Gaetano Giorgini, 
in the 29th vol. of the Annales de Chimie, there is another in 
the 57th vol. of that Journal, p. 148, by M. Bossingault. This 
philosopher also remarks, ‘ La cause qui peut influer sur V’in- 
salubrité de certaines contrées, se développe constamment 1a 
ov la matiére végétale morte est exposée a I’action de la 
chaleur et de Vhumidité. Elle est propre 4 tous les pays 
chauds et marécageux ou 4 ceux qui sont entourés de foréts 
étendues. Son action se manifeste surtout d’une maniére terri- 
ble 1a ow il se fait un mélange d’eaux douces et d’eaux salces, 
a embouchure de grands fleuves, ou sur le littoral des golfes.’ 
M. Boussingault alludes to many instances occurring within the 
tropics in America, whereby it is proved, that vegetable mat- 
ters putrefying by the influence of heat and humidity, spread 
infection over the neighbourhood of the most destructive kind. 
The resultsobtained by MM. Moscati, Rig awd, and Boussingault, 
prove sufficiently, that, in a marshy country, during the preci- 
pitation of dew, an organic matter is deposited with it, which 
blackens sulphuric acid. This matter is flocky, and, like an 
animal substance, contains nitrogen. M. Boussingault says, 
‘On peut méme congevoir l'efficacité de certaines précautions 
qui ont été indiquées pour se preserver de leurs effets, On a dit, 
par exemple, qu il suffisait de se couyrir la figure d’un voile. 
J'ai vu, en effet, plusieurs fois, dans les marais du Cauca, les 
personnes obligées de les parcourir, s’entourer le visage Vun 
mouchoir de maniére a ne respirer qu’a travers le tissu.” 
