, 1912-10-12

world. In a wider sense, it is recognized
that the existence or planting of forests is
not concerned merely with the problem of
timber supply, but that each possesses q large
Importance arising from the employment of
forests as an aid in water conservation, and
for the purpose Of protecting certain local.
ties, such as catchment areas for water sup
ply, from pollution or other harm. The re-
lation of forests to water conservation gains
an additional interest when it IS viewed IN
the aspect Of the suggestion, supported by
some, that their presence increases ptecipi-
tatiOn.
A useful summary* of this part of the sub
iect that has appeared recently, commences
by drawing attention to the amount of in
v~estigation of the question of the influence
Of forests on rainfall that has been made III
France, Germany aud Austria, in the United
States, and more recently III India, and
points ont that the literature of the subject
is somewhat ~bewildering, both on account
Of it's extent aud Of the divergent views Of
the different authorities. One manner Of at
lacking the problem is the historical method.
In this the state of an area of country as re-
CARDS It's forest cover is compared Will the
amount of rainfall over a period for which
statistics are available, the latter being often,
in the absence of reliable rainfall records,
supplied by accounts Of the condition over a
long time of a stream or river which may be
considered to be influenced by the forest III
or near its basin. Among the objections to
this method is the ignoring Of effects due to
Secular climatic changes, and it is also open
to the criticism that forests are known to as
sist in increasing the amount of water, avail
able for streams, in ways other than that
which suppJses an increase III the rainfall.
Observations in India + have been consid-
cred to show that the presence of wooded
areas has II beneficial influence upon rainfall,
an increase of eight to fifteen pei cent,
having been suggested. Results bearing the
opposite Interpretation have been obtained
in the United States some of them are pre-
scented III ii paper contained IL q report to
the United States House Of Representatives
on the influence Of forests on climate and
floods. The conclusions in the paper indi-
cate that there is strong evidence for Lhe in
ability Of the removal Of forests to influence
rainfall it is that the latter controls the rate
of forest growth rather than that the amount
of forest cover influences the rainfall the
conditions thut affect rainfall exist at such
an altitude as to prevent the way in which
the land is covered locally from possessing
any influence. Actual, careful observations
show that there has been no noticeable
change in the rainfall in the United States,
during the time that such observations have
been possible.
The advocates Of the theory that forests
induce rainfall try to find confirmation of
their views IN the results that have been OBJ
tanned by making simultaneous observations,
ut stations called parallel stations, in q forest
urea and IN the open surrounding country.
In nearly every place where these obser-
vations have been carried out, o larger rain
tall has been indicated on the land under
forest 50 that it is held that forests increase
precipitation. II this conclusion could be
proved definitely to be correct, the circum-
stance would be of the greatest Importance,
for it is easy t+4oe-thaT the effect would ex-
tend beyond the forest area, because the
wind would bear away the r0in-carrying
clouds that had been formed. The oppo-
hents have been interpreted correctly ex-
perimeuts, they say, have demonstrated that
gauges situated in the forest register d
great r rainfall than those in the open be-
cause they are sheltered from the wind. At
tempts to allow for this influence have been
made, but the matter is SO uncertain that
those who hold the theory cannot be said
IN