Sacramento daily record-union. [volume] (Sacramento [Calif.]) 1875-1891, 1884-02-16
FORMATION OF RAIND1oPs.

Various theories have been advanced to
account for the formation OF raindrops, but
the mos. satisfactory explanation is that
proposed by Professor Osborne Reynolds.
The minute particles of which clouds are
composed are moving downward in conse-
ouence OF the attraction of gravity ; but
by reason of the resistance which the air
offers to their descent, they are only NOV
ing very slowly. Since, however, the re.
sistance offered to the passage Of large
drops is much smaller in proportion to
their weight than that offered to small
drops, it 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 all 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 a particle descending
from the upper part of the cloud
may become rsindrop of consid-
cradle size before it energies from the
cloud. In their 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, or may be slightly diminished
by partial evaporation from the surfaces of
the drops. a falling raindrop descends
with velocity which increases until the
acceleration is balanced by the resistance
of the air, after which the drop descends
with uniform velocity. It is, Of course,
well known that large clouds may exist
without any rain falling from them. In
some cases rain is actually formed, but
vapor before it can reach the ground in
many cases the transformation of rain is
possibly due to the fact that under certain
unknown 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
disintegrstion OF rocks and the formation
of soils, washes the smaller particles into
streams and rivers, and is, in fact, one
of the most important OF the various de-
nuding agents. Indeed, 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 earta's surface. The amount of the
rainfall varies very considerably in differ.
ent countries and in different parts of the
same country, depending on geographical
position, the conformation 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 Gains over the
equatorial region of the Atlantic and Pa.
cific Oceans and on the west coasts of The
British Isles, India, Norway, North and
South America and New Zealand. In all
these latter districts the west wind blows
over large tract of ocean and becomes
heavily charged with moisture, which it
deposits when forced upward by the a. on
of the mountains on the coasts. The driest
districts in the world are the desert regions
of Africa and Asia. The amount of rain
which falls in single showers is sometimes
enormous, especially in the tropics. In
the British Isles one of the heaviest falls
on record is fall of SO inches in "A hours
in Monmouthshire, July IA, 1875. On o.
tober %, 1886, at Gibraltar there was a
fall of 80 IL inches [Cassells Concise
CvcIorpdia