Part 424

At*mol"o*gist (&?;), n. One who is versed in atmology.

At*mol"o*gy (&?;), n. [Gr. &?; vapor + - logy.] (Physics) That branch of science which treats of the laws and phenomena of aqueous vapor. Whewell.

At*mol"y*sis (&?;), n. [Gr. &?; vapor + &?; a loosing, &?; to loose.] (Chem.) The act or process of separating mingled gases of unequal diffusibility by transmission through porous substances.

At`mol*y*za"tion, n. (Chem.) Separation by atmolysis.

At"mo*lyze (&?;), v. t. (Chem.) To subject to atmolysis; to separate by atmolysis.

At"mo*ly`zer (&?;), n. (Chem.) An apparatus for effecting atmolysis.

At*mom"e*ter (&?;), n. [Gr. &?; smoke, vapor + -meter: cf. F. atmomètre.] An instrument for measuring the rate of evaporation from a moist surface; an evaporometer. Huxley.

At"mos*phere (&?;), n. [Gr. &?; vapor (akin to Skr. tman breath, soul, G. athem breath) + &?; sphere: cf. F. atmosphère. See Sphere.] 1. (Physics) (a) The whole mass of aëriform fluid surrounding the earth; -- applied also to the gaseous envelope of any celestial orb, or other body; as, the atmosphere of Mars. (b) Any gaseous envelope or medium.

An atmosphere of cold oxygen. Miller.

2. A supposed medium around various bodies; as, electrical atmosphere, a medium formerly supposed to surround electrical bodies. Franklin.

3. The pressure or weight of the air at the sea level, on a unit of surface, or about 14.7 Ibs. to the sq. inch.

Hydrogen was liquefied under a pressure of 650 atmospheres. Lubbock.

4. Any surrounding or pervading influence or condition.

The chillest of social atmospheres. Hawthorne.

5. The portion of air in any locality, or affected by a special physical or sanitary condition; as, the atmosphere of the room; a moist or noxious atmosphere.

{ At`mos*pher"ic (&?;), At`mos*pher"ic*al (&?;), } a. [Cf. F. atmosphérique.] 1. Of or pertaining to the atmosphere; of the nature of, or resembling, the atmosphere; as, atmospheric air; the atmospheric envelope of the earth.

2. Existing in the atmosphere.

The lower atmospheric current. Darwin.

3. Caused, or operated on, by the atmosphere; as, an atmospheric effect; an atmospheric engine.

4. Dependent on the atmosphere. [R.]

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. Tomlinson. -- Atmospheric line (Steam Engin.), 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 under Tide.

At`mos*pher"ic*al*ly (&?;), adv. In relation to the atmosphere.

At`mos*phe*rol"o*gy (&?;), n. [Atmosphere + -logy.] The science or a treatise on the atmosphere.

At"o*kous (&?;), a. [Gr. &?; barren; 'a priv. + &?; offspring.] (Zoöl.) Producing only asexual individuals, as the eggs of certain annelids.

A*toll" (&?;), n. [The native name in the Indian Ocean.] A coral island or islands, consisting of a belt of coral reef, partly submerged, surrounding a central lagoon or depression; a lagoon island.

At"om (&?;), n. [L. atomus, Gr. &?;, uncut, indivisible; 'a priv. + &?;, verbal adj. of &?; to cut: cf. F. atome. See Tome.] 1. (Physics) (a) An ultimate indivisible particle of matter. (b) An ultimate particle of matter not necessarily indivisible; a molecule. (c) A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.

These three definitions correspond to different views of the nature of the ultimate particles of matter. In the case of the last two, the particles are more correctly called molecules. Dana.