Smithsonian miscellaneous collections . II. ON THE MAINTENANCE OF A DIFFERENCE OFPRESSURE BY THE ADDITION OF HEAT (7.) STEADY CIRCULATION IN A DRY ATMOSPHERE During movements of the air out of regions of higher pressureinto regions of lower pressure, work is being expended continuouslyby the pressural forces drawing from a previously accumulatedsupply. The potential energy of the system must exhaust itselfand the differences of pressure at any level must disappear, unlessthere be compensation from some source. Movements againstthe gradient could indeed reconvert kinetic energy into potentialen
Smithsonian miscellaneous collections . II. ON THE MAINTENANCE OF A DIFFERENCE OFPRESSURE BY THE ADDITION OF HEAT (7.) STEADY CIRCULATION IN A DRY ATMOSPHERE During movements of the air out of regions of higher pressureinto regions of lower pressure, work is being expended continuouslyby the pressural forces drawing from a previously accumulatedsupply. The potential energy of the system must exhaust itselfand the differences of pressure at any level must disappear, unlessthere be compensation from some source. Movements againstthe gradient could indeed reconvert kinetic energy into potentialenergy, but then the process would develop some sort of waveaction and even then the loss by friction must be replaced. So far as the study of energy is concerned, one can imagine ascheme for a steady circulation between regions of differing pres-sures as explained in the following diagram and text. MECHANICAL EQUIVALENT OF PRESSURE MARGULES 521 Heat abstracted Temperature . . r« xPressure p. Pressure . higher P xTemperature .... 7. Heat added (i) At the lower level the air flows from the higher pressure Pvto the lower P2 and at the same time receives an increase of the sake of the analysis we assume that the adiabatic changeof condition prevails in the passage from Pt to P2 and that therehas therefore been a cooling from Tl to T2 but that then anaddition of heat under the pressure P2 suddenly takes place, pro-ducing a rise from T2 to T2. (2) An adiabatic ascent at the location of lower pressure P2 andabove it a vertical equilibrium prevails or a condition inappreciablydifferent therefrom, so that the pressure falls to p2 and the tem-perature falls to t2. (3) A horizontal movement along the upper level from p2 to p1together with cooling by radiation or conduction; this process willfor convenience in analysis be decomposed into adiabatic changeof condition from p2 z2 to pl r2 then abstraction of heat and coolingfrom z2 to tx under the pressure px to such an extent that,
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