154 
PROTECTION AGAINST MALARIA. 
of the Alps ; that fruit trees thrive well no longer, and that i* 
is difficult to raise young trees.* 
f. Trees as a Protection against Malaria . 
The influence of forests in preventing the diffusion of mias¬ 
matic vapors is a matter of less familiar observation, and per¬ 
haps does not come strictly within the sphere of the present 
inquiry, hut its importance will justify me in devoting some 
space to the subject. “ It has been observed ” (I quote again 
from Becquerel) u that humid air, charged with miasmata, is 
deprived of them in passing through the forest. Rigaud de 
Lille observed localities in Italy where the interposition of a 
screen of trees preserved everything beyond it, while the 
unprotected grounds were subject to fevers.” f Few European 
countries present better opportunities for observation on this 
point than Italy, because in that kingdom the localities ex¬ 
posed to miasmatic exhalations are numerous, and belts of 
trees, if not forests, are of so frequent occurrence that their 
efficacy in this respect can be easily tested. The belief that 
rows of trees afford an important protection against malarious 
influences is very general among Italians best qualified by 
intelligence and professional experience to judge upon the 
subject. The commissioners appointed to report on the meas¬ 
ures to be adopted for the improvement of the Tuscan Ma- 
remme advised the planting of three or four rows of poplars, 
Populus aZba, in such directions as to obstruct the currents of 
air from malarious localities, and thus intercept a great pro¬ 
portion of the pernicious exhalations.” % Lieutenant Maury 
even believed that a few rows of sunflowers, planted between the 
Washington Observatory and the marshy banks of the Poto¬ 
mac, had saved the inmates of that establishment from the 
intermittent fevers to which they had been formerly liable. 
* JJeber die Entwaldung der Gebirge , p. 28. 
t Becquekel, Des Climats, etc., p. 9. 
X Salvagnoli, Rapporto sul Bonijkamento delle Maremme Toscane, pp. 
xli, 124. 
