DAMP  , a

common Teutonic word, meaning vapour or mist (cf . Ger . Dampf, steam), and hence moisture . In its primitive sense the word persists in the vocabulary of coal-miners . Their " firedamp " (formerly fulminating damp) is marsh gas, which, when mixed with air and exploded, produced " choke damp," "after damp," or " suffocating damp " (carbon dioxide) . " Black damp " consists of accumulations of irrespirable gases, mostly nitrogen, which cause the lights to burn dimly, and the term " white damp " is sometimes applied to carbon monoxide . As a verb, the word means to stifle or check ; hence damped vibrations or oscillations are those which have been reduced or stopped, instead of being allowed to die out naturally; the " dampers " of the piano are small pieces of felt-covered wood which fall upon the strings and stop their vibrations as the keys are allowed to rise; and the " damper " of a chimney or flue, by restricting the draught, lessens the rate of combustion .