Height of the Atmosphere
المؤلف:
GEORGE A. HOADLEY
المصدر:
GEORGE A. HOADLEY
الجزء والصفحة:
p-176
2025-11-11
34
The compressibility of the air is so great that the layer in contact with the surface of the earth is denser than the layers above it. Though the density constantly decreases as the distance. from the earth increases, no uniform rule can be given that will show the relation between barometric readings and the corresponding heights of the atmosphere. However, a fall of one inch in the mercury column, from the reading at sea level, indicates an elevation of about 900 ft
Figure 1 is a graph showing the relation (in fair weather) between height above the surface of the earth in feet and the pressure of the atmosphere as measured by inches of mercury. It is seen from this curve that at a height of 20,000 ft. the pressure is reduced from 31 in. of mercury to less than 15, which means that the density of the air is not half so great at that height as at the surface.
Balloon ascensions have exceeded this height, notably that of Mr. James Glaisher, undertaken for the purpose of making scientific observations for the British Association for the Advancement of Science. Both Mr. Glaister and his aeronaut, Mr. Coxwell, became unconscious, but before losing consciousness succeeded in letting enough gas escape to bring the balloon down into the denser atmosphere. The pressure recorded by the instruments indicated height of 37,000 ft. The height of 36,020 ft. was reached on February 27, 1920, by Major R. W. Schroeder, who drove an airplane from McCook field, Dayton, Ohio. The extreme cold at this height rendered him temporarily blind. His machine fell five miles but was righted at 2000 feet and made a safe landing.
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