Also 5 torcion, 6 -syon, 7 tortion, [a. F. torsion (1314 in Littré, in sense 2 below), ad. late L. torsiōn-em (Vulg.), by-form of tortiōn-em, n. of action from L. torquēre, tort-um to twist, wring. Cf. Pr. torsio, Sp. torsion, Pg. torsão; also It. torzione, ad. L. tortiōnem.]
1. The action of twisting, or turning a body spirally by the operation of contrary forces acting at right angles to its axis; also the twisted condition produced by this action; twist.
Angle of torsion, (a) the angle through which one end of a rod or other body is twisted while the other end is held fast; (b) Geom. the infinitesimal angle between two consecutive osculating planes of a tortuous curve. Balance of torsion = torsion-balance: see 3.
1543. Traheron, Vigo’s Chirurg., VI. i. 180. Yf the dislocation be lytle, so that the bone be not out all togyther, it is called dislocation not complete, and it is it which commonly is called torsion, or wresting.
1658. Phillips, Torsion, a wresting, or wringing of any thing.
1807. T. Young, Lect. Nat. Phil., I. 140. Torsion, or twisting, consists in the lateral displacement, or detrusion, of the opposite parts of a solid, in opposite directions, the central particles only remaining in their natural state. Ibid., 141. The force of torsion, as it is determined by experiment, varies simply as the angle of torsion.
1814. R. Buchanan, Shafts Mills, 24, note. Journals, or journeys, are gudgeons subject to torsion.
1834. Nat. Philos., III. Hist. Astron., xxi. 105/2 (Usef. Knowl. Soc.). By means of a delicate instrument, called the balance of torsion, the attraction of a leaden sphere, eight inches in diameter, was made sensible.
1835. Ure, Philos. Manuf., 106. With very short filaments like those of wool, cotton, and cachemire, a thread of the greatest length may be formed by torsion.
1859. J. Tomes, Dental Surg., 163. Torsion, or twisting of the central incisors upon their axis, is far from rare.
1867. Thomson & Tait, Nat. Phil., I. I. § 608. The fundamental principle that spiral springs act chiefly by torsion seems to have been first discovered by Binet in 1814.
b. A twisting of the body or a part of it; contortion, distortion. rare.
1660. F. Brooke, trans. Le Blanc’s Trav., 89. They ejulate, weep, and lament with exotick gestures, and tortions.
1899. Allbutt’s Syst. Med., VII. 242. During the flexions and torsions of the vertebral column.
c. Surg. The twisting of the cut end of an artery to stop hæmorrhage.
1835–6. Todd’s Cycl. Anat., I. 224/2. The successful employment of torsion of the arteries as a means of suppressing hæmorrhage.
1878. T. Bryant, Pract. Surg. (1879), II. 5. Any bleeding taking place can usually be checked by cold styptics, or torsion.
d. Bot. The condition of being twisted spirally.
1875. Bennett & Dyer, trans. Sachs’ Bot., 772. A distinction must be drawn between two kinds of torsion; firstly, that of erect organs; and secondly, that of organs … in a horizontal or oblique position. In the former case the torsion results from internal conditions of growth, and especially from the outer layers growing more rapidly than the inner ones.
† 2. Path. A wringing or griping of the bowels; tormina. Obs. (The earliest sense in Eng.)
c. 1425. trans. Arderne’s Treat. Fistula, 78. It availeþ … to euery inflacion of þe wombe, and to ventosite of it, and torcions, i.[e] gryndyng.
1543. Traheron, Vigo’s Chirurg., III. Wounds, I. ii. 100. Knowen by the greate payne, and torsyon or grypynge of the bellie.
1626. Bacon, Sylva, § 39. All Purgers have in them a raw Spirit, or Winde; which is the principall Cause of Tortion in the Stomach, & Belly.
1689. Moyle, Sea Chyrurg., III. vii. 109. Sometimes there is … intolerable tortion of the Bowels.
3. attrib. and Comb., as torsion arm, axis, circle, pendulum, screw, spring; torsion-balance, an instrument for measuring minute horizontal forces, consisting of a wire or filament having a horizontal arm to the end of which the force is applied so as to make it revolve and twist the wire, etc., through an angle proportional to the twisting moment of the force; torsion-basin Geol., a basin formed by torsion of the earth’s crust in any region; torsion-curve, a curve caused by torsion; torsion electrometer, an electrometer that measures by means of a torsion-balance.
1831. Holland, Manuf. Metal, I. 199. It does not appear that these torsion nails have ever found much favour.
1837. Brewster, Magnet., 15. The torsion balance, for measuring small forces.
1873. Maxwell, Electr. & Magn., § 38. The torsion-balance was devised by Michell for the determination of the force of gravitation between small bodies, and was used by Cavendish for this purpose. Ibid., § 215. The angle through which the electrical force twisted the torsion-arm. Ibid., § 725. The torsion-screw, which turns the torsion-head round a vertical axis.
1884. F. J. Britten, Watch & Clockm., 265. Small clocks … are made with torsion pendulums.
1899. Mar. M. Ogilvie-Gordon, in Nature, 7 Sept., 445/1. Two great internal torsion-basins, within the Alpine systems of southern Europe, are the Hungarian and the west Mediterranean. Ibid. (1901), 24 Jan., 294/1. I wrote my paper on the ‘Torsion-structure of the Dolomites’ in 1898. Ibid., 295. The torsion-curves round the northern periphery of the Adriatic crust-basin.
Hence Torsionless a., not subject to torsion.
1858. Herschel, Outl. Astron., I. iv. (ed. 5), 160. A metallic arc … supported from its middle … by a torsionless suspension.
