Rogue River courier. (Grants Pass, Or.) 1886-1927, 1909-04-30

cept that the air retards the diffu-
sion of the vapor particles. II is
more correct to say that the space is
partly saturated with moisture, or
that the moisture is in a partly sat
urated condition. Whenever water
vapor begins to precipitate from the
atmosphere 1t is an indication that
the temperature of the dew point has
been reached The temperature of
the dew point, therefore, simply
means that point, or that tempera-
ture, where precipitation will take
place. Supposing that we observe
with our pyschrometer that the dew
point is S5 degrees; then we know
that If the atmosphere were to cool
so that thermometer would regis
ter 80 degrees, dew would begin to
form Again, suppose that the dew
point was found to be twenty de-
grees, then if the atmosphere cool
ed to 20 degrees frost would appear,
and not at any temperature above 20
degrees. BY this we see that al
though freezing would take place
long before the thermometer regis
tered 20 degrees, there would be no
vidence of it through the appear
ance of white frost. This pheno-
menon is often termed black
frost" The important considera-
tion, of course, is the connection be-
tween the temperature of the dew
point and the occurrence OF frost, or
freezing temperatures. When the
dew point temperature is low, we
know that the amount of water va
por in the atmosphere is small. We
also know that the amount Of water
vapor in the atmosphere governs, to
a very large extent, the temperature
of the atmosphere. When the at
mosphere contains a considerable
amount Of water vapor, which, of
course, means a high dew point,
rapid changes Of temperature do not
usually occur, especially when there
are no winds. When the dew point
temperature is low, rapid changes
do occur, since the point at which
the water vapor may give up some of
its heat is low. Water vapor, as well
as other substances, has that prop
erty which is known as latent heat
For instance, we know that water at
the boiling point has temperature
at sea level, of 212 degrees. We also
know that steam, which Is nothing
more than water vapor, at the same
pressure, also has temperature OF
PIP degrees. However, in causing
steam to form, considerabl,
amount of heat has been used. TIL,
steam in cooling so as to form water
lets so Of this heat. Now, whel
water yapor condenses at any dev
point temperature, heat Is liberated
II there Is a considerable amount o
water vapor in the atmosphere the
there is, In proportion, more hea
which may be liberated. This ex
plains the reason why, when the dey
point is high, killing frosts rarely oc
cur. In speaking of low dew poin
temperatures, ! may state that W
may consider for this section, at thi
season Of the year, any temperatur
below 35 degrees as near the DANCE
point, providing the sky is clear an
there is no wind.
, In closing, may say that thl
years work has shown the effective
ness Of smudge fires. With a
abundance of cheap material, It hg
been found to be very ineXpensiN
when compared with the results
be obtained. It is certain that u
. one should fear frosts in this vale
when 1t is so easy to protect again
=, them. At most the frosts have n,
, been severe as compared with mo
Of The fruit sections Of the countr
and there is no reason for any unce
- tain feeling as regards the future
~ the fruit industry in the Rogue Riv
, valley. Another year, with a loc
- weather bureau official in the Va
- ley, and with the proper sort
preparation, anticipate no furth
;, difficulties =. j. O'GARA,
Assistant Pathologist, T. S. Depal
+, ment OF Agriculture.
More Hose Remnants Sc and /
- foot at Cramer Bros.