Evening star., 1901-08-24
Weather Expert Dunn Gives Hot
Weather Advice.
THROW AWAY THE THERMOMETERS
How to Regulate Your Living and
Avoid Suffering.
DEATHS FROM EXHAUSTION
Written for The Evening star by r. b. Dunn.
0lnnrrichf 1any

written Tor The Evening star by r. B. Dunn.
Copyright. I90l)
1t requires no great prophetic power or
distinctive weather judgment to arrive at
the determination OF what causes most
discomfort during the summer months.
Most people would say offhand that the OBJ
jectionable element is heat, and that per-
sona comfort is In inverse ratio to the
changes of the thermometer. but lit
| tie thought will bring out the fact that the
element which causes the actual suffering
during hot weather is humidity
From the term humidity we understand
| II to be moisture in the air. and its pres
| ence is determined by means of hygro-
meters, the amount being expressed In per
cent form. The hygrometer is formed of
| two ordinary thermometers, one being dry
and the other having a piece OF linen
wrapped around the bulb and kept thor
oughly saturated with water. especially be-
fore taking an observation. To get the
true readings. both instruments should be
whirled around so that evaporation may
| be more rapid than when the instruments
are motfonless, and at the same rate OF
| speed at each reading, so as to obtain the
true amount of moisture present and elm
mate q. difference in the force of evapora-
| ton. II the whirling Of the thermometers
| did not take place the wind force and evap-
oratton would be different at each reading,
4
lutte amount of moisture present.
BY relative humidity we understand the
condition OF the air when considered in
connection with the temperature. Thus it
| will be seen that humidity involves two
| elements; first. the amount of vapor pres
| ent; second, the amount which would thor
| oughly saturate the air at the actual tenn
| perature when the reading is made. It Is
upon the ratio Of these elements that our
sensations Of dryness and moisture are ex-
| perienced. The greater the difference OBJ
served in the reading Of the dry and wet
thermometers the greater the dryness of
the air: the closer the reading, the greater
the moisture IL they read exactly the
same 1t would mean that the air was thor
| oughly saturated and held all the moisture
it was possible to contain at that tempera-
ture, that is, 100 per cent. When 1t reaches
that point. however. condensation In the
shape Of rain. snow, sleet or fog must
| take place. either heavy or light, to make
place for the moisture that Is being con-
stantly taken up by the force of evapora-
ton, which goes on at all times under all
temperatures and conditions. It is not to
be understood that 1t Is necessary for the
humidity to reach 100 per cent before con-
densation takes place; rain or snow may
fau when the humidity registers 40 per
cent or even less. but condensation inva-
riably takes place in some form when 100
per cent of humidity is registered.
In New York city the average humidity
high on the seacoast and decreases as the
distance into the interior increases.
A Simple Illustration.
The air In a room heated by a hot stove
may contain as much vapor, weight for
weight. as the open air outside, but 1t is
dryer, because warm air expands, making
its capacity for holding moisture greater
In like manner, the air at noon Is dryer
than at midnight, though the amount of
yapor present be the same, and it is dryer
in summer than in winter, though the
l. amount Of nrpSqnf q When
air containing aqueous vapor is gradually
cooled its density gradually increases and
the rate of increase is sensibly the same
for yapOr as for dry air, with which 1t Is
mixed, until point Is reached at which
the density of the vapor becomes equal to
the maximum density possible at a given
temperature. This temperature is called
the dew point, and any further reduction Of
temperature will cause condensation OF q
portion Of the vapor in the shape of rain,
snow, dew. fog, frost or sleet, according to
1t is found that many of our storms pro-
ducing rain along or near the seacoast
occur in the evening or shortly after the
warmest part Of the day. The winds blow
from the ocean, carrying in excessive
amount OF moisture. until the humidity
registers from normal to the point OF sat
uration. Then, as the GOODNESS Of night
comes on, the atmosphere contracts and its
capacity for holding all the moisture which
1t has taken up during the day Is dimin-
ished, and there Is partial condensation:
this condensation may not anQrd much
relief, as Is often found to be the case. for
the atmosphere has only thrown on its
surplus caused by contraction. and Is still
charged to its full capacity according to the
temperature prevailing at the time. How
ever, 1t Is usually found that after we
have been boiled or steamed through a hot
summer day. there is usually some relief
from thunder storms OF this kind, even II
the air Is sti11 moisture laden: the streets
and houses have been partially cooled by
the rain It is seldom ON our coast that
some relief Is not afforded by thunder
storms during the heated terms in less than
three days: in this respect we are better
off than our neighbors in the interior OF
the country; they do not suffer from hu-
midity as we on the coast do. but their
heated spells last much longer than ours,
and very little relief Is afforded In thun-
der storms
What We Caa Stand.
Human beings can stand a temperature OF
from 100 to 125 degrees for a long period
without any great discomfort II the air is
dry but inject into that same air enough
moisture to increase the humidity from Is
to 20 per cent above its normal amount
and the people who are subjected to It
would die of from exhaustion in few
days. A good Illustration OF what nature
will stand in the line Of dry heat is DEM
onstrated every day by the stokers on the
large steamers and some OF the firemen in
Dur large factories and buildings. Their
fire rooms are heated up to more than 100
degrees for days and months. and still there
is no more injury to health complained Of
than from people who are walking the
streets during the hot days Why? Sim
ply because the moisture In the overheated
fire room has been taken up by the exces-