Pressure 



27 



density are important differences in the pressure, inertia, viscosity, 

 and mobility of tlie media. 



PRESSURE 



The difference in the densities of the media results in a great 

 difference in the rate of change of pressure at increasing altitudes in 

 the atmosphere and at increasing depths in the water. Near the 

 earth's surface a rise of 300 m ( 1000 ft ) in altitude results in a reduc- 

 tion of pressure of about 25 mm Hg, or a relatively slight change in 



AIR 



Rates of change: 

 25 mm Hg/300 m 



22 mm Hg 



235 mm Hg 



310 mm Hg 



367 mm Hg 

 413 mm Hg 



760 mm Hg = 1 Atmos. 



|- 25,400 m - Rocket-powered plane 

 22,000 m ■ Stratosphere balloon 



8840 m (29,000 ft) - Mt Everest 



— 7000 m ■ Vultures and eagles 



— 5800 m - Wild sheep and ibex 



4860 m • Highest human settlement, Tibet 

 4420 m - Mt Whitney. California 



1920 m ■ Mt Washington, N. H. 

 Sea level 



1 Atmos/ 10 m 



WATER 



370 Atmos. 



625 Atmos. 



925 m Deepest dive of bathysphere (Beebe) 

 1400 m Deepest dive of benthoscope (Barton) 



3700 m Average depth of oceans 



4050 m Deepest dive of bathyscaphe (Houot) 



6250 m Ten species of animals taken by 

 "Challenger" 



— 10,500 m Various invertebrates taken by "Galathea" 

 1086 Atmos. L io,860 m (35,640 ft) ■ Greatest ocean depth 



(Mariana Trench) 

 Fig. 2.3. Range of pressure in air and water in relation to the distribution of life. 



