The Manitowoc pilot. [volume] (Manitowoc, Wis.) 1859-1932, 1884-03-27
Rain.


Various theories have been advanced
to account for the formation of rain
drops, but the most satisfactory ex-
planation is that proposed by Professor
Osborne Reynolds. The minute parti-
cles of which clouds are composed are
moving downward in consequence of
the attraction of gravity; but, by rea-
son OF the resistance which the air of
ters to their descent, they are only mov-
ing very slowly. Since, however, the
resistance offered TO the passage of
large drops is much smaller in proper
| ton to their weight than that offered
to small drops, il follows that the large
| drops will descend faster than the
smaller ones, and will overtake them,
| coming into collision with any which
are in the direct line of their descent.
| When two drops collide they will
unite to form larger drop, which
will descend with increased velocity,
sweeping up smaller drops in its path,
| and thus increasing in size until it
emerges from the cloud. Since MANY
clouds are several miles in thickness. it
is easy to see that Il particle descending
from the upper part of the cloud may
become drop OF considerable size be-
lore 1t emerges from the cloud. In
thelr passage from the cloud to the
earth the larger raindrops will overtake
the small ones in precisely similar
way. AT the same time the size of the
drops may be slightly increased by the
condensation of water from the air
through which they are falling, r..
may be Slightly diminished by rsrtiaI
nV1nnTq tlnn frnr1, bn
drops.
A falling raindror descends with a
velocity which ir.creases until the ac-
celetsuoh y balanced by the resistance
" eae ar, after which the drop de-
soS,-ds with uniform velocity. 1t is, of
, course, well known that large clouds
may exist without any rain falling
| from them. IL some cases rain is act
ually formed, but eyaporates and is
I again converted into vapor before it
can reach the ground; in many cases
the non-formation of rain is possibly
| due to the fact that under certain un-
known atmospheric or other conditions
| the particles forming the clouds do not
unite when they collide. As an agent
| of geological change rain is of the
greatest Importance. 1t plays large
| part in the disintegration of rocks and
the formation of soils, washes the
smaller particles into streams and riv-
ers, and is in fact one of the important
of the various denuding agents. In
| deed, since rain is the ultimate source
of all our brooks, rivers, etc., it may
be said to be the principal agent of
| geological change on the earth's sur
face. The amount of the rainfall
varies very considerable in different
| parts of the same country, depending
on geographical position, the confor-
nation of the surface of the ground.
the proximity of large lakes and the
| sea, etc. The heaviest annual fall of
rain occurs in the zone OF calms over
| the equatorial region of the Atlantic
| and Pacific Oceans and on the west
coasts of the British Isles, India, Nor
| way, North and South America and
| New Zealand. In all these latter dis
tricts the west wind blows over a large
tract of ocean and becomes heavily
charged with moisture, which it de-
posits when forced upward by the ac-
ton of the mountains on the coasts.
The driest districts in the world are
| desert regions of Africa and Asia.
The amount of rain which falls in sim
gle showers is sometimes enormous,
| especially IN the tropics. In the Brit
ish Isles one of the heaviest falls on
record is a fall of Sc inches in TWEEN
| ty four hours, in Monmouthshire, July
ID, 1875. On October 25, 1886, at Gil
braltar, there was fall of 80 II inches,
-C0SSetPS Concise CuciOpe0ia