The Florida agriculturist. [volume] (DeLand, Fla.) 1878-1911, 1881-03-16
Atmospheric Humidity.
Written for the Ftorid0 Agriculturist, By Dr. C
j. KensoorthY. M. ID.
(CO1atineled from poge 337.)

r.
j. KenscOrtha. M. ID.
(CO'etinsted from poge 337.
The term relative humidity is a
convenient one to express the COM
parative dryness of the atmosphere.
Complete saturation being assumed
TO be 100 per cent. absolute dryness
0. Hence any degree of saturation
may be expressed as a per centage OF
saturation--it one quarter, or one
halt saturated it is said to contain 25
or 90 per cent. of moisture. The
health OF any given section (more
especially if warm climate) is to a
great extent dependent on the dry
ness or moisture Of the atmosphere.
Professor Tyndall's observations
have shown how greatly the humidity
OF the atmosphere influences climate,
by hindering the transmission of the
suns rays to the earth, and from the
earth to space. A certain amount of
moisture IN the air is an important
factor OF climate. Perfectly dry air
allows heat.to pass through it with
out being sensibly warmed thereby !;
but moisture i'll the air presents an
obstruction to the free passage OF the
heat of solar and terrestrial radiation.
This is undoubtedly one OF the most
important and conservative functions
OF the invisible moisture OF the at
mosphere. For if the moisture was
removed from it, and its diather.
NANCY rendered complete the suns
rays would burn up everything by
their tierceness, and during the night
the escape of heat by radiation to the
cold stellar space would be so swift
and the cold SO intense, that the
whole living creation would be
blighted by its wilhering touch.
The earth would ..feel by turns the
bitter change of fierce extremes, ex.
tremes by changemTe fierce frombeds
{, of raging fire 10 etarye in ice. The
spread of certain diseases is supposed
to be intimately related to humidity
of the air. Malarious diseases, it is
said, never attain their fullest epi-
demic influence unless the humidity
approaches saturation. Recent re-
searches tend to prove that autumn
nal fevers are Of germinal origin and
dependent upon fungus named
Bacillus mdLdriGL Heat and moisture
are necessary tor the development of
germs, and may we not account for
the intrequency and mildness of au-
tumnal ievers in a large portion of
this State. Plague and small pox
are checked by very dry atmos,
phere. The cessation of the Bubo
plague in upper Egypt, after a certain
date has been considered to he more
owing to the dryness, than to the
heat of the air. In the southern por.
ton of Australia, extensive marshes
exists, and dry up during the sum-
mer months. The thermometer
range is very high {; and all factors
except a moist atmosphere exists tor
the production of autumnal fevers,
and yet they are almost unknown.
The atmosphere is remarkable for
its dryness, and it is probable that
the germinal cause OF autumnal
tevers cannot be propagated in a dry
and dessicating climate. In the dry
Harmattan wind, on the west coast
OF Africa, small pox cannot be inocu-
lated; and it is well known with
what difficulty supply OF vaccine
virus is kept up in very dry seasons
in India. Thermometric range SO
much relied on by persons when
they discuss climates, has less to do
with health, and suffering from heat
than the moisture contained in the
atmosphere. One of the most i'm
portant consequences of evaporation
Is the loss OF heat which accompanies
it. During the conversion OF a
liquid into the gaseous form, very
large quantity of heat disappears !;
and since it becomes imperceptible
10 the senses, or to the thermometer
as long as the gaseous state is re.
tanned, the heat is said to become la
tent. The change OF water to vapor
by evaporation, is productive OF cold,
and the conversion OF vapor to water
productive OF heat. II the atmos-
\ phere contains much moisture, heat
! is oppressive, it il is comparatively
dry, persons do not suffer from a