TREES AS A SHELTER. 
149 
e. Trees as a Shelter to Ground to the Leeward. 
The action of the forest, considered merely as a mechanical 
shelter to grounds lying to the leeward of it, would seem to be 
an influence of too restricted a character to deserve much 
notice ; but many facts concur to show that it is an important 
element in local climate, and that it is often a valuable means 
of defence against the spread of miasmatic effluvia, though, in 
this last case, it may exercise a chemical as well as a mechan¬ 
ical agency. In the report of a committee appointed in 1836 
to examine an article of the forest code of France, Arasro 
observes : “ If a curtain of forest, on the coasts of Normandy 
and of Brittany were destroyed, these two provinces would 
become accessible to the winds from the west, to the mild 
breezes of the sea. Hence a decrease of the cold of winter. 
If a similar forest were to be cleared on the eastern border 
of France, the glacial east wind would prevail with greater 
strength, and the winters would become more severe. Thus 
the removal of a belt of wood would produce opposite effects 
in the two regions.” * 
This opinion receives confirmation from an observation of 
Dr. Dwight, who remarks, in reference to the woods of New 
England : “ Another effect of removing the forest will be the 
free passage of the winds, and among them of the southern 
winds, over the surface. This, I think, has been an increasing 
fact within my own remembrance. As the cultivation of the 
country has extended farther to the north, the winds from the 
south have reached distances more remote from the ocean, and 
imparted their warmth frequently, and in such degrees as, 
forty years since, were in the same places very little known. 
This fact, also, contributes to lengthen the summer, and to 
shorten the winter-half of the year.” f 
It is thought in Italy that the clearing of the Apennines 
has very materially affected the climate of the valley of the 
Fo. It is asserted in Le Alpi che cingono ITtalia that: In 
* Beoquerel, Des Climate, etc., Discours Prelim, vi. t Travels , i, p. 61. 
