at the approach of difficulty or danger. One who is fluctuating in his feelings is usually vacillating in
resolve, and wavering in execution.
(Fluc"tu*ate), v. t. To cause to move as a wave; to put in motion. [R.]
And fluctuate all the still perfume.Tennyson.
(Fluc`tu*a"tion) n. [L. fluctuatio; cf. F. fluctuation.]
1. A motion like that of waves; a moving in this and that direction; as, the fluctuations of the sea.
2. A wavering; unsteadiness; as, fluctuations of opinion; fluctuations of prices.
3. (Med.) The motion or undulation of a fluid collected in a natural or artifical cavity, which is felt when
it is subjected to pressure or percussion. Dunglison.
Flue boiler. See under Boiler. - - Flue bridge, the separating low wall between the flues and the
laboratory of a reverberatory furnace. Flue plate (Steam Boiler), a plate to which the ends of the
flues are fastened; called also flue sheet, tube sheet, and tube plate. Flue surface (Steam
Boiler), the aggregate surface of flues exposed to flame or the hot gases.
(Flue) n. [Cf. OF. flue a flowing, fr. fluer to flow, fr. L. fluere (cf. Fluent); a perh. a corruption
of E. flute.] An inclosed passage way for establishing and directing a current of air, gases, etc.; an air
passage; esp.: (a) A compartment or division of a chimney for conveying flame and smoke to the outer
air. (b) A passage way for conducting a current of fresh, foul, or heated air from one place to another.
(c) (Steam Boiler) A pipe or passage for conveying flame and hot gases through surrounding water in
a boiler; distinguished from a tube which holds water and is surrounded by fire. Small flues are called
fire tubes or simply tubes.
(Flue) n. [Cf. F. flou light, tender, G. flau weak, W. llwch dust. &radic84.] Light down, such as
rises from cotton, fur, etc.; very fine lint or hair. Dickens.
(Flu"ence) n. Fluency. [Obs.] Milton.