4. Dependent on the atmosphere. "In am so atmospherical a creature." (Pope) Atmospheric engine, a steam engine whose piston descends by the pressure of the atmosphere, when the steam which raised it is condensed within the cylinder.
<engineering> Atmospheric line, the equilibrium line of an indicator card. Steam is expanded "down to the atmosphere" when its pressure is equal to that of the atmosphere. (See Indicator card) Atmospheric pressure, the pressure exerted by the atmosphere, not merely downwards, but in every direction. In amounts to about 14.7 Ibs. On each square inch. Atmospheric railway, one in which pneumatic power, obtained from compressed air or the creation of a vacuum, is the propelling force. Atmospheric tides. See Tide.
Origin: Cf. F. Atmospherique.
(01 Mar 1998)
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