vapor, vapour, wapure

[Fr. vapeur, from Lat. vaporem, acc us. of vapor =vapor; Sp. & Port. vapor; Ital. vapore.] I. Ordinary Language: 1. Literally: (1) In the same sense as II. (2) Any visible diffused substance floating in the atmosphere and impairing its transparency, as fog or mist; hazy matter. "From the damp earth impervious vapors rise." Pope: Statius; Thebaid, i. 486. *(3) Wind, flatulence. "Ointments, if laid on anything thick, by stopping up the pores, shut in the vapors , and send them to the head extremely." -Bacon . 2. Figuratively : (1) Something unsubstantial, fleeting, or transitory; unreal fancy; vain imagination. "He hath the grace of hope, though it be clouded over with a melancholy vapor ." - Hammond . *(2) ( Pl .): A hectoring or bullying style of conversation or mode of behavior, indulged in by swaggerers for the purpose of bringing about a real or mock quarrel, consisting in flatly contradicting whatever was said by a speaker, even if the bully had granted what was a erted just before. "They are at it still, sir; this they call vapors ."- Ben Jonson: Bartholomew Fair , iv. 3. *(3) ( Pl .): A disease of nervous debility, in which a variety of strange images float in the brain, or appear as if real; hence, hypochondriacal affections; depre ion of spirits; dejection, spleen; the blues. II. Physics: An aëriform fluid into which some volatile substance is changed by the action of heat. Vapor is e entially the same as gas, but the word vapor is conventionally limited to the gaseous state of a body which is liquid or solid at ordinary temperatures, while the term gas is applied to aeriform bodies which are in that rarefied state at ordinary temperatures. Thus we speak of hydrogen gas, but of watery vapors. Vapors, like gases, have a certain elastic force, by which they exert a pre ure on every part of any ve el in which they are enclosed. Vapors are formed instantly in a vacuum; in the atmosphere they are generated more slowly. When not saturated they exactly resemble gases in their action; when saturated and in contact with the liquid by which they were generated, they can neither be compre ed nor expanded, but remain constant, both in their elastic force and in their density. Vapors of different composition vary in density. Thus if atmospheric air be taken as unity, the vapor of water=0-6235, that of alcohol 1.6138, that of sulphur 6.6542, and that of mercury 6.9760.