Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1885-06-17

How Discrepancies I'm Thermometer Marks
May Be Explained.
The general fact that the tempera-
ture of the air varies with different
levels above the earth's surface has
long been recognized. Meteorologists
tell us that there is usually fall of
one degree Fahr. for every 800 feet of
ascent above the sea level, with certain
variations for local causes. We may
call this a meteorological thermal fuc-
tuation, and it is always marked by
fall of temperature with increased ele-
vation. But there is an equally i'm
portant change of temperature in the
opposite direction, of great Importance
to the farmer and fruit-grower, name
ly, loss of temperature as we descend
into valleys. In early years 1 was
country doctor. and had to take many
long ride in the night The road
passed from a high bluff into deep
valley, with another bluff on the oppo-
site side. When the air was still I
could detect by the change of temper
ature the transition from the warm air
of the bluffs to the chilly air of the val
ley. 1t was like passing into a cold
stream of water, and the change was
equally abrupt on passing into the
warm air on the opposite bluff.
l appreciate the fact that ones feel
ings can hardly be accepted as re-
liable test of temperature, and thai
thermometer is better than sensation
to furnish reliable physical data. The
temperature of the open air. for any
given locality. and for the same time,
is supposed by most persons to be
definite and uniform quantity. If two
persons in the same neighborhood re-
port different temperatures for the
same hour, it is supposed that such
difference must arise from a difference
n the correctness of the thermometers,
or some accidental variation of ex-
posure, it being assumed that the
temperature of the open air" for a
given locality and Identical time would
be the same. Many persons suppose it
IS very simple thing to determine the
temperature Of the open air; it is only
necessary to hang the thermometer out
doors till it has reached point of no
iuctuation and then read off the tenn
Derature by the thermometer scale.
! But when trial is made even with ther-
nometers that compare favorably with
each other under identical conditions, a
marked d screpancY is often observed
| rlaccs near Weigh hborhOo@
This is especially true if the sher-
mometerS are at different levels and
there is no nd. We treat of air un-
| der the head of pneumatics, whereas it
sometimes comes rather under the
head of hydraulics, for cold air fows IN
| currents the same as tfa1ids. In the alb
sence of wind VIII ch mixes up the
strata of air of different temperatures,
and consequently of different specific
| gravity, the cold air of the night will
flow in streams and gather in ponds or
lakes the same as water. Under such
circumstances the temperature will
vary tn the level, and the subject of
thermal levels becomes matter of m
portance. have made many observa-
tions to determine the difference of
temperature with slight dffere ces of
elevation. An open air thermometer
hangs at the north door of my labora-
tory, adjusted to avoid accidental va
riations of temperature. Aravine runs
through the college lawn near the lab
oratory. A thermometer was placed
in he ravine $50 feet from the one by
the laboratory door and twenty-five
feet below its level In very cold
weather, when the air was very still, I
have occasionally seen the thermome-
ter IN the ravine mark eight degrees
below the thermometer at laboratory
door.
During the cold weather of last
month I again examined the relative
temperature at these two points, select
ing mornings with little wind for such
observations and reached the following
results: