Sounding the Ocean of Air: Being Six Lectures Delivered Before the Lowell Institute of Boston, in December 1898Rotch, Abbott Lawrence
Science
Sounding the Ocean of Air: Being Six Lectures Delivered Before the Lowell Institute of Boston, in December 1898
Rotch, Abbott Lawrence
Atmosphere; Balloons; Clouds; Kites (Meteorology)
Some of the deductions from the observations with kites at Blue Hill
follow. Plate VIII. is a facsimile of the record of the
baro-thermo-hygrograph during two flights on October 8, 1896, when for
the first time the height of a mile and a half was attained. The
record-sheet, it may be said, is wrapped around a cylinder that turns
on its axis in twelve hours, and the curved lines in each of the three
horizontal sections divide them into quarter hours. The lower section
contains the trace of the barometer, the horizontal lines being the
heights in metres and feet that correspond to the barometric
pressure with a temperature of 32∞ Fahrenheit; in the middle section
is the trace of the hygrometer on a scale of relative humidity in
percentages, and in the upper section is the trace of the thermometer
on a scale of temperatures in Fahrenheit and Centigrade degrees. It
will be observed that the record of the barometer is reversed, _i.e._
the trace rises for falling pressure, and in the second flight when
the unexpected height of 8697 feet above Blue Hill was reached, the
limit of the altitude scale was exceeded.
[Illustration: PLATE VIII.--METEOROGRAM FROM THE KITE-FLIGHT OF
OCT. 8, 1896, AT BLUE HILL.]
In order to study the changes of these elements with height during the
higher flight, in Plate IX., Figs. 4 and 5, the temperature and
humidity of the automatic record are plotted as abscissÊ, with the
heights above sea-level in metres as ordinates. For those not familiar
with this unit of length, it may be said that 100 metres are about 330
feet, and that 1600 metres equal one mile approximately. When the
meteorograph was ascending, dots indicate the recorded temperatures
and humidities, which are each connected respectively by continuous
lines; when the meteorograph was descending, crosses indicate the
observations, which are connected by broken lines. Lines inclining
upwards to the left indicate decreasing temperature and humidity with
increase of height, and lines inclining to the right increasing
temperature and humidity with height. The straight dotted lines show
the adiabatic decrease of temperature for ascending dry air. The
ascent was made during the warmest part of the day, and the descent
for the most part after sunset. The two branches of the
temperature-lines typify the temperature change with height which
usually occurs in fair weather during the day and the night
respectively. The continuous line, representing the day observations,
shows a uniform fall of temperature at the adiabatic rate to the cloud
level. During the night, the lower part of the broken line bends
decidedly to the left, showing a body of relatively cold air near the
ground, caused by radiation. There is a rise of temperature with
increasing altitude above the ground up to a certain height, and
afterwards a comparatively uniform fall as high as the clouds, if they
exist; but the rate of fall with increasing altitude, shown by the
Public-domain text, read in full here on John Shaqi.
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