Year: 1873

cially large ones, have tendency to preserve
a temperature oe their own, more equable
than that of the surrounding atmosphere,
owing to the flow of sap through their cells,
or to some other cause. When nocturnal
radiation commences, if the sky be without
clouds, in proportion as the upper leaves and
branches become cool, those which are UNDER
meath yield up their heat in succession to
those above through the process of radiation.
From this it will be readily perceived that
the stratum of air which envelops the tree
retains, through greater part Of the night,
temperature higher than the strata Of air
which are remote from it. Thus a large
collection of trees preserves higher tenn
perature during the night and during the
winter, and lower temperature during the
summer, than the surrounding atmosphere
that is, produces a more equable tempera-
ture throughout the year Of the region in
which it is situated


Forests exert a marked influence on the
temperature of region, in proportion as
they shelter from the prevailing winds. The
laws of the motion Of the atmosphere are
similar to those Of water. A naked hill,
however high it may be, gives no protection,
for the wind passes over it as water pours over
Il DAM But if the hill be capped with trees,
the windy cascade will be broken as into
spray, and its violence will be sensibly di-
minished. A mass Of trees will of course, afford
protection in proportion to the density Of their
mass, and their height above the surrounding
country. Nevertheless, a single tree affords
shelter in almost any situation. 1t is well un.
derstood that forests principally act asa shelter
against the lower winds but this influence
is vast as will readily be seen, especially on
elevated regions or extensive plains and
prairies. This influence would depend much
upon the oblquity of the wind which would
be different in different parts Of the world.
We are scarcely aware on the now protected
and irregular surface of New England, how
important are the screens furnished by the
forests. Those who have Travelled in the
prairies Of that section the wind is almost
always fresh, and often blows gale before
which men can hardly stand Settlers there
are glad to shelter their habitations under
the lea of the spurs Of forests, when possible.
In any part of New England forest near
the coast protects those farther inland from
the chilling east winds


The value of trees as shelter 10 domestic
animals from the sum- is well known to farm
ers and herdsmen. In the breeding and
iattening of cattle, sheltered farm is
thing much priced; and in instances where
fields are taken by the season for this pur.
pose, those most sheltered never fail to bring
the highest rents. Large tracts OF pasture
should be subdivdcd into smaller lots,
which should have trees planted around their
borders, and over their surfaces. 1t is best
that trees OF some kind should be allowed to
grow in all parts Of a pasture, so that cattle
may not have far to GO, in sultry hour, to
obtain comfortable shade.


Small lots, thus sheltered suffer more
snow to remain upon their surfaces during
winter, and are not left bare so soon in the
spring, as larger lots without shelter; since
fences and trees cause more Of it to remain on
the ground.


OF not less value are trees as shelter to
crops from the wind and gardeners, horti-
culturists, and others, take advantage of this
by planting hedges to protect their tender
shrubs and fruit trees. A garden surround.
ed by tall trees, even in our severe climate,
admits Of the cultivation Of plants almost
tropical. The experiment Of Mr.. Tudor, Of
Nahant, which resulted in converting bar
rem piece Of land exposed to sea blasts into
fertile and productive garden, by means of
a screen formed OF high fences, shows the
value to crops of shelter from the winds.
Numberless such facts might be adduced,
were it necessary.


Another use of forests is to serve as con.
ductors of electricity between the clouds and
its great reservoir the earth, thus giving ac-
tivity to the vital powers of plants, and
causing the clouds to discharge their con-
tents upon the earth A few tall trees, even,
on the summit Off hill, are sufficient toproduce
this effect. A charged thunder cloud, which
passes unbroken over bare hill, will pour
down its moisture, il its electricity is drawn
off by these natural conductors.


| Continued Hfrt irftkJ