a. and sb. [f. L. longitūdin-, longitūdo LONGITUDE + -AL.]

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  A.  adj.

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  1.  Of or pertaining to length as a dimension; (extent) in length.

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1765.  Blackstone, Comm., I. 275. Oar antient historians inform us, that a new standard of longitudinal measure was ascertained by king Henry the first.

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1796.  Morse, Amer. Geog., II. 270. The real depth, or longitudinal extent of the mine.

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1810.  D. Stewart, Philos. Ess., II. I. i. 223. To express a limited portion of longitudinal extension in general.

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1818.  Cobbett, Pol. Reg., XXXIII. 182. The number of longitudinal inches of the foot measure.

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  2.  Extending or proceeding in the direction of the length of a body; running lengthwise.

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  Longitudinal elevation: one showing the side of a structure, as distinguished from an end view; a side elevation.

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1715.  Cheyne, Philos. Princ. Relig., I. (ed. 2), 134. These Vesiculæ are distended, and their Longitudinal Diameters … straitned, and so the length of the whole Muscle shortned. Ibid., 518. The oblique Fibres which make but few turns serve to propagate gently the included Fluid, the Longitudinal ones to move the Vessel.

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1794.  Sullivan, View Nat., II. 3. The great longitudinal vallies of the Alps.

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1807.  M. Baillie, Morb. Anat. (ed. 7), 394. A longitudinal section was made with a saw completely through its substance.

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1825.  J. Nicholson, Operat. Mechanic, 564. If two pieces of timber are connected, so that the joint runs parallel with the fibres of both, it is called a longitudinal joint.

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1839.  Murchison, Silur. Syst., I. xxviii. 529. By longitudinal valleys is meant those which range parallel to the ridges or general strike of the mountains.

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1845.  Darwin, Voy. Nat., ii. (1879), 7. Several of the species are beautifully coloured with longitudinal stripes.

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1860.  Tyndall, Glac., I. xii. 88. The glacier … is in a state of longitudinal strain.

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1861.  Beresf. Hope, Eng. Cathedr. 19th C., 81. I have selected … the longitudinal elevation and the longitudinal and transverse sections … for their intrinsic merit.

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  b.  Anat. and Zool.

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1706.  Phillips (ed. Kersey), Longitudinal Suture (in Anat.), the cross Seam of the Scull, that goes from one Side to the other.

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1826.  Kirby & Sp., Entomol., IV. 298.

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1840.  W. J. E. Wilson, Anat. Vade M., 361. The longitudinal fissure is the space separating the two hemispheres.

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1854.  Owen, Skel. & Teeth (1855), 3. The head of the sturgeon is defended by a case of superficial bony plates, and the body by five longitudinal rows of similar plates.

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1863.  Huxley, Man’s Place Nat., iii. 142. The two depressions for the lateral sinuses, sweeping inwards towards the middle line of the roof of the skull, to form the longitudinal sinus.

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1870.  Rolleston, Anim. Life, 1. The longitudinal fissure in which is lodged the longitudinal sinus.

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  c.  Bot.

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  Longitudinal system, ‘an old term for fibro-vascular system’ (Jackson, Bot. Terms, 1900).

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1787.  Linnæus’ Fam. Plants, I. 76. Petals four, egg’d, sessile, with a longitudinal pit at the base.

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1884.  Bower & Scott, De Bary’s Phaner., 565. The beginning of the formation of lenticels takes place … before longitudinal extension is complete.

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1888.  Syd. Soc. Lex., Longitudinal system.

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  d.  Acoustics. Of vibrations: Produced in the direction of the length of the vibrating body; also (see quot. 1869).

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1867.  Tyndall, Sound, v. 159. The sounds produced by the longitudinal vibrations of a string are, as a general rule, much more acute than those produced by its transverse vibrations. Ibid. (1869), in Fortn. Rev., 1 Feb., 239. In the case of sound, the vibrations of the air-particles are executed in the direction in which the sound travels. They are therefore called longitudinal vibrations.

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1879.  W. H. Stone, Sound, 13. Longitudinal Vibrations. Every string which vibrates transversely between two points must also vibrate longitudinally.

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  3.  Pertaining to longitude; measured from east to west.

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1874.  Coues, Birds N. W., 360. Its longitudinal dispersion is thus quite restricted, contrary to the rule among our birds of this … continent.

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  B.  sb.

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  † 1.  Anat. A name for two muscles of the epigastrium. Obs.

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1541.  [see LATITUDINAL sb.].

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  2.  Ship-building. In iron and steel ships, a plate parallel or nearly so to the vertical keel.

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1869.  Sir E. Reed, Shipbuild., i. 10. To preserve the continuity of their longitudinals.

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1883.  Nares, Constr. Ironclad, 5. Longitudinals are plates of iron, which run fore and aft between the frames, to strengthen the ship lengthways.

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1900.  Engineering Mag., 678. The stiffening angles for longitudinals.

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  3.  A railway sleeper lying parallel with the rail (Webster, 1864).

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