Fluid

a. and sb. Also 7 fluide. [a. Fr. fluide, ad. L. fluid-us, f. fluĕre to flow; see -ID.]

  A.  adj.

  1.  Having the property of flowing; consisting of particles that move freely among themselves, so as to give way before the slightest pressure. (A general term including both gaseous and liquid substances.)

1603.  Holland, Plutarch’s Mor., 1361. To comprehend a substance and essence thereof, you shal doe as much good as if you would cluch water in your hand with a bent fist; for the more you seeme to gripe and presse together that which of the owne nature is fluid and runneth out, so much the more shall you leese of that which you will claspe and hold.

1638.  Wilkins, New World, I. xii. (1640), 178. The appearance of the milky way dos not arise from some fluider parts of the heaven (as he supposes) but from the light of many lesser starrs which are thereabouts.

1667.  Milton, P. L., VI. 344.

1711.  Pope, Temp. Fame, 446.

1756.  C. Lucas, Ess. Waters, III. 315. The salt fuses readily, and runs very fluid.

1845.  Darwin, Voy. Nat., xxi. (1852), 493. Volcanic bombs, that is, masses of lava which have been shot through the air whilst fluid, and have consequently assumed a spherical or pear-shape.

  b.  fig. and of non-physical things: Flowing or moving readily; not solid or rigid; not fixed, firm, or stable.

1642.  H. More, Song of Soul, I. II. iv.

1672.  Cave, Prim. Chr., II. ii. (1673), 31. The fluid and transitory condition of mans life (says he) calls for a daily reparation of the decays of nature.

1719.  De Foe, Crusoe, II. i. 290. I mean the French; whose Temper is allow’d to be more volatile, more passionate, and more sprightly, and their Spirits more fluid than in other Nations.

1873.  M. Arnold, Lit. & Dogma (1876), p. xv. To understand that the language of the Bible is fluid, passing, and literary, not rigid, fixed, and scientific, is the first step towards a right understanding of the Bible.

1885.  Academy, XXVII. 6 June, 400/1. Indicating a time when the evangelical tradition was still fluid.

  2.  Of speech, etc.: Flowing easily and clearly. † Of a speaker: Fluent.

1691.  Wood, Ath. Oxon., II. 355. He [Edmund Bunney] was the most fluid Preacher in the Reign of Qn. Elizabeth, for he seldom or never studied for what he was to deliver, but would preach and pray extempore.

c. 1789.  Gibbon, Mem., Misc. Wks. 1796, I. 159. Monsignor Stonor, a prelate of the same nation, who discovers much venom in the fluid and nervous style of Gibbon.

  B.  sb.

  1.  A substance whose particles move freely among themselves, so as to give way before the slightest pressure.

  Fluids are divided into liquids, which are incompletely elastic, and gases, which are completely so.

1661.  Boyle, Spring of Air, I. iv. (1682), 10. The Air being a fluid as well as a heavy body.

a. 1721.  Keill, Maupertuis’ Diss., iii. (1734), 19. Descartes to account for the Revolutions of the Planets around the Sun, supposes them imerged in a Fluid, which circulating around that glorious Star, forms the vast Vortex which sweeps them along, just like a Vessel when left to the Tide of a River.

1807.  Med. Jrnl., XVII. 275. From the first he swallowed fluids with difficulty, more so at some times than at others, as the spasms were more or less violent.

1813.  Sir H. Davy, Agric. Chem. (1814), 13. The true use of water in vegetation was unknown till 1785; when Mr. Cavendish made the grand discovery, that it was composed of two elastic fluids or gases, inflammable gas or hydrogene, and vital gas or oxygene.

1882.  Minchin, Unipl. Kinemat., vi., heading. Kinematics of Fluids.

  b.  spec. Any liquid constituent or secretion of the body (or of a plant).

1704.  F. Fuller, Med. Gymn., Preface. Moderate exercise, by Augmenting the Natural Heat of the Body, will enrich the Fluids.

1732.  Arbuthnot, Rules of Diet, 259. By which Principles they are heating, and act strongly both on the Fluids and Solids.

1804.  Knight, in Phil. Trans., 186. Gravitation will act on the fluid descending from the leaves; and these will, of course, absorb from the atmosphere with increased activity.

1831.  R. Knox, Cloquet’s Anat., 3. The fluids constitute the greater part of the organs, their quantities varying, however, according to circumstances.

1844.  Hoblyn, Dict. Med. Terms, Fluid of Cotunnius. A thin gelatinous fluid, found in the bony cavities of the labyrinth of the ear; so called from the name of the anatomist who first distinctly described it.

1878.  L. P. Meredith, Teeth, 49. They decay on account of the bad condition of the fluids of the mouth, caused by the giving away of the temporary teeth and the little attention paid to cleanliness.

  2.  One of several subtle, imponderable, all-pervading substances, whose existence has been assumed to account for the phenomena of heat, magnetism, and electricity.

1750.  Franklin, Lett., Wks. 1840, V. 246. The pores are so narrow, that the particles of the electrical fluid, which enter both surfaces at the same time, cannot go through.

1832.  Nat. Philos., Magnetism, iv. § 152. 36 (Useful Knowl. Soc.). The theory with respect to magnetism which has of late more generally prevailed, is founded on the supposition, that its phenomena are occasioned by the agency of two magnetic fluids, residing in the particles of iron…. They have been denominated respectively the Austral and Boreal fluids.

1881.  Maxwell, Electr. & Magn., I. 38. In most expositions of this theory the two electricities are called ‘Fluids,’ because they are capable of being transferred from one body to another, and are, within conducting bodies, extremely mobile.

  3.  Comb. as fluid-containing adj.; also fluid compass, lens (see quots.).

1753.  N. Torriano, Non-Naturals, 50. The Fluid-containing Vessels.

1867.  Smyth, Sailor’s Word-bk., Fluid compass, that in which the card revolves in its bowl floated by alcohol.

1874.  Knight, Dict. Mech., I. 891/1. Fluid-lens. One in which a liquid is imprisoned between circular glass disks of the required curvatures.