340 dtalian Malaria. 
abundance in different parts of Italy and Sicily which are neverthe- 
less considered as very healthy. 
The effect has also been imputed to exhalations of azotic gas ; but 
this gas being lighter than atmospheric air would necessarily rise and 
thus render the heights more unhealthy than the vallies, while experi- 
ence proves that the contrary is the fact.* 
The Campagna of Rome is an extended country, cut up by little 
hills and mostly in an uncultivated state. During the rainy season, 
the water collects in the vallies and forms pools where it stagnates, 
and having brought with it all sorts of vegetable substances as well 
as animal refuse, it becomes corrupted. At the return of the warm 
season which augments the putrefaction, these ponds and marshes 
send forth their vapor, but as the process of evaporation goes on 
slowly, the heat being still moderate, the atmosphere is not much 
changed until the month of July brings with it a greatly increased 
temperature, which accelerates the evaporation, and which is accom- 
panied by fevers whose duration equals its own; that is to say, it is 
prolonged to September. 
If the Campagna were every where properly cultivated, as it was 
formerly, the air would not be subject to this alteration ; for the rains 
of winter would not then collect as they do in the low grounds, but 
would be absorbed by a mellowed soil, and evaporated by the influ- 
ence of the heat. 
Tt must not be urged against this opinion, that in Lombardy, espe- 
cially in the plains which extend from Bologna to Férrara, the vast 
fields of Rice are, during the whole winter, covered with water, and 
that the country is nevertheless not unhealthy, or at least not so much 
so as that of Rome. These artificial lakes or mundations, as I have 
myself observed, are first, on account of their extent, always agitated 
by the wind, like a lake of water, and also by the action of the sluices 
by which they are supplied and drained, the current of water is con- 
tinually entering and passing from them. ‘These two causes com- 
bined prevent putrefaction. 
* While we admit, with the author that azotic gas is not the probable cause of 
epidemic fever, we must object to the soundness of his conclusion, with respect to 
its elevation. Although somewhat lighter than atmospheric air, it is, we believe 
most conformable to established facts in chemistry, to conclude that the particles of 
any gas, if set free in the atmosphere, will [ultimately] arrange themselves in the 
same manner as if the atmosphere itself did not exist, provided they have no affinity 
for, or do not combine with constituents of the air. Such is the Daltonian theory, 
which we believe has never been disproved.— Trans. 
