Light Science for Leisure Hours: A series of familiar essays on scientific subjects, natural phenomena, &c.Proctor, Richard A. (Richard Anthony)
Science
Light Science for Leisure Hours: A series of familiar essays on scientific subjects, natural phenomena, &c.
Proctor, Richard A. (Richard Anthony)
Science
I may point out in this place the important connection which exists
between the rainfall of a country and the amount of forest land. I
notice that in parts of America attention is being paid—with markedly
good results—to the influence of forests in encouraging rainfall. We
have here an instance in which cause and effect are interchangeable.
Rain encourages the growth of an abundant vegetation, and abundant
vegetation in turn tends to produce a state of the superincumbent
atmosphere which encourages the precipitation of rain. The consequence
is, that it is very necessary to check, before it is too late, the
processes which lead to the gradual destruction of forests. If these
processes are continued until the climate has become excessively dry,
it is almost impossible to remedy the mischief, simply because the
want of moisture is destructive to the trees which may be planted to
encourage rainfall. Thus there are few processes more difficult (as
has been found by experience in parts of Spain and elsewhere) than
the change of an arid region into a vegetation-covered district. In
fact, if the region is one of great extent, the attempt to effect
such a change is a perfectly hopeless one. On the other hand, the
contrary process—that is, the attempt to change a climate which is too
moist into one of less humidity—is in general not attended with much
difficulty. A judicious system of clearing nearly always leads to the
desired result.
The dryness of the past year has not been due to the want of moisture
in the air, nor to the exceptionally unclouded condition of our
skies. I believe that, on the whole, the skies have been rather more
cloudy than usual this year. The fact that so little dew has fallen
is a sufficient proof that the nights have been on the whole more
cloudy than usual, since, as is well known, the presence of clouds,
by checking the radiation of the earth’s heat, prevents (or at least
diminishes) the formation of dew. The fact would seem to be that the
westerly and south-westerly winds which usually blow over England
during a considerable part of the year, bringing with them large
quantities of aqueous vapour from above the great Gulf Stream, have
this year blown somewhat higher than usual. Why this should be it
is not very easy to say. The height of the vapour-laden winds is
usually supposed to depend on the heat of the weather. In summer, for
instance, the clouds range higher, and therefore travel farther inland
before they fall in rain. In winter, on the contrary, they travel
low, and hence the rain falls more freely in the western than in the
eastern counties during winter. A similar relation prevails in the
Scandinavian peninsula—Norway receiving more rain in winter than in
summer, while Sweden receives more rain in summer than in winter. But
this summer the rain-clouds have blown so much higher than usual as to
pass beyond England altogether. Possibly we may find an explanation
Public-domain text, read in full here on John Shaqi.
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