The times., 1901-06-09

ers" and "thunderstorrns may be used.
Local rain and showers are almost iden-
teal in meaning. The word thunder
storm" of course. carries its own signfi-
canoe. Any one of these terms indicates
that the rain will not be general over
the whole State or district. The most
marked feature of precipitation in the
warm season, as compared with the cold,
, is its unequal distribution over relatively
| small areas. A shower cloud may form
| and pass over several counties or it may
| diSSipate within five miles of its origin.
! Indeed. we may say that it is only in eN-
| CeDtional cases that general and contlnu-
| Gus rains fall in the summer season. In
| some seasons local rains may occur in
| some part of a State every day of the
month. but the science of meteorolngy is
I not yet far enough advanced to delimit
the path Of local shower and the exact
! time ef its occurrence. Forecasts of local
rains, showers. or thunderstorms indicate
| that the conditions are favorable for the
| occurrence Of precipitation in the district
and for the given period.
Clearing is a word frequently used,
! which carries a broader meaning than
! the word itself signifies, viz, the occur
| of the period, thus. Clearing tonight
would indicate that rain or snow, which
| ever might be falling at the beginning of
| the period. would cease shortly there
after, and the weather would he clear
during the greater part of the time.
Persons whose working hours are large
| " spent in the open air soon become IA
IniIiar with the changing aspects OF the
SKY. and the condition Of the atmosphere
as to its moisture content. viz. whether
relatively dry or humid. If careful OBJ
| servers Of natural phenomena. they note
also the shift of the wind. and the Sc
queDCe Of weather which follows In
these and without special effort a fund of
weather wisdom is soon acquired which
needs only 10 be properly correlated in
order to serve most useful purpose. The
greatest advantage will naturally accrue
to the individual who reads and accu-
ratCiy interprcts, not only the Govern
mcnt forecasts, but also the local wealth
er signs.
CLOUDS AND THEIR FORMATION
Clouds are formed from the moisture
that is always i'm the air, in varying guam
titles, even over the desert. Like the air
itself the moisture that is within it is
invisible so long as it remains in the form
of u gas When mass of air is cooled
by any means whatsoever. a portion of
its water VapOr IS condensed and becomes
visible-a mist or cloud is formed A IA
miliar illustration of cloud formation in
nature is affOrGed when a current of
warm moist air strikes a cloud mountain.
iht colder surface OF the mountain con-
denseS some of the moisture that is in
the air. forming cloud which frequent
lE ObScures the top of the mountain and
floats away in the prevailing winds This
simple phenomenon indicates to an obseTv-
ct on the leeWard side of the mountain
that a warm, moist current of air. with
probably rain or snow is approaching. In
some parts Of the world the formation of
a cloud cap on mountain top is not an
indication of precipitation. yet in the ma
iorIrN of cases u IS believed to be re-
liable prCguOStic of falling weather. In
general rhe formation of cloud after a
clear spell is the sign of coming rain.
Unfortunately there is no definite inter
val between the time Of the first appear
ance OF clouds and the occurrence of rain.
Rain may not fall for several days after
the first appearance of clouds. and, on
the other hand. it may begin within two
or three hours after the first cloud makes
its appearance
An increase in the amount of moisture
in the air is indicated in various ways
it is especially noticeable in the senses
when coupled with a high temperature.
Man does not need a thermometer to tell
him that the air is oppressiyely warm,
nor a hySrOmttcr to tell him that there |
is an unusual amount of moisture pres
ent- pitcher of ice water on a hot |
summer day is not a bad sort OF hy-
grometer- The pitcher is naturally cooler |
than the surrounding air. and conse-
QUently some Of the water TapOr in the |
air is condensed and collects on the out
side of the pitcher. The water vapor !
changes 10 the liquid state when the air |
is cooled TO below q certain point. The |
principle illustrated IN the pitcher of ice |
water is repeated on a grand scale in |
ma ture every time rain or snow fails. |
First. there is the cooling of the air and |
eiis loi NAHUM u d t.vuu' tit idLlef Ne
ing composed of minute particles of |
water, second, there is the further cool |
ing Of the cloud mass, so that its parti- |
cles Join to form small raindrops, which |
fan TO the earth by their own weight. |
When the rain cloud strikes the top of |
a mountain rain does not necessarily /
fall. but small mist-like particles Of |
water are deposited on the relatively |
colder surfaces of the rocks and other |
objects on the mountain sides and top.
These particles coalesce and run down l
the sides Of the objects on which they
are deposited precisely as frequently hap |
pens on a pitcher of ice water on a
warm. humid day. If the mountain were |
warmer than the cloud mass there would |
be no condensation. but some of the
moisture Of the cloud would be eVap- !
)Tated and float away in the wind
An unusual amount OF moisture in the