Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1866-08-30
The Origin of Esrairies.

At the annual meeting of the t" American
Scientific Association" held at Buffalo last
week, Prof. ]. S. Newberry read an in
structive paper on this subject, Of which
the following is an abstract:
DIR. Newberry said that great diversity
Of opinion existed as to the causes which
had produced over half our continent a
growth of forests, and over the other half
only an herbacious vegetation, but in this,
as in so many other questions that divided
the scientific world, if the disputants could
meet on common ground, and each study
the phenomena observed by others, and not
exclusively his own data, there would be
comparatively little discord. He had spent
some years on the prairies in various parts
of the far West, and he fell confident that
any one who would go over the ground he
had traversed would agree with him that
the presence or absence of forests as a gen.
eral rule depended on the amount of pre-
cipitated moisture. The central portions
of this continent, as others, are compare
lively dry, and were consequently treeless,
except on the mountain belts, which acted
as condensors, and precipitated an amount
of water which sustained a forest growth.
The rainfall was greaterin that part of the
continent east of the Mississippi, and here
we have an almost unbrOken forest.
Along the line where the treeless and for
est districts meet, local causes determine
the presence or absence of trees. Belts of
timber bordered the streams and covered
the more porous and absorbent soil-while
level surfaces, with q fine unporous soil
sometimes very wet and sometimes very
dry, sustained only growth of grass, which
could endure, their alterations, fatal to
trees. Annual fires had their influence in
extending the area of grassy surface, and
over much of this grassy surface, aud over
much of this middle GROUND, by mans in
vention, the causes limiting the growth of
trees could be removed and their forest area
extended. The forces Of nature we're here
nicely balanced, and slight causes would
make one or the other preponderate. The
many theories which attributed prairies to
other causes than want Of water were
wholly erroneous, of only local value. On
the great prairies west of the Mississippi,
every variety of soil and surface failed to
sustain trees, and there only change of
climatic conditions would change the grass
covered surface to forest.
CLEARNEss OF THE AIR IN CoLoRADo.-A
Colorado correspondent gives the following
illustrations of The extreme limpidity of the
atmosphere in Colorado:
Immediately in front of US rise the two
shattered and worn fragments of what was
once an immense ball of red stone they
look 100 feet distant, and 80 feet high, when
in point of fact they are not less than 1000
feet off, with an elevation of something like
800 feet. Perhaps you say, What is the
matter with your eyes? Can't you tell 100
feet from 1000, or see the difference be-
tween so and 300?' Why, yes, can under
ordinary circumstances, but here, in this
wonderful atmosphere, distance is lost. To
continue. Beyond the red stone fragments
rises a hill, beyond that two mountains, the
second higher than the first, obscuring from
our view all the peak below a point higher
than the line of vegetation. The peak
appears to be so near as to be fully within
the range of cannon shot. Very well. Now
the distance TO the peak is just % miles"