Also 6 eroysion. [a. Fr. erosion, a. L. ērōsiōn-em, n. of action f. ērōdĕre: see ERODE.]
1. The action or process of eroding; the state or fact of being eroded. Spec. in Geol.: cf. ERODE v. 2.
1541. R. Copland, Guydon’s Quest. Chirurg., 2 A ij b. Holowe vlceres … procede of two causes, that is to wete of excysyon and of eroysion. Ibid., 2 A iij b. Erosion.
1612. Woodall, Surg. Mate, Wks. (1653), 383. Or by extream erosion or corrosion of caustick Medicines or corrosive humours.
1753. N. Torriano, Gangr. Sore Throat, 60. The Erosion or Rupture of the Vessels.
1774. Goldsm., Nat. Hist. (1862), I. xiv. 75/2. And it is happy for man that bounds are thus put to the erosion of the earth by water.
1813. J. Thomson, Lect. Inflamm., 369. The phenomena which it [ulcerative absorption] exhibits were denominated erosion by Galen.
1836. Todd, Cycl. Anat., I. 450/2. The erosion or absorption of the cartilages.
1851–9. Darwin, Geol., in Adm. Man. Sci. Enq., 294. Where ranges of cliffs exist the marks of the erosion of the waves may sometimes be expected to occur.
1854. Woodward, Mollusca, iv. (1856), 41. We can often recognise fresh-water shells, by the erosion of those parts where the epidermis was thinnest.
b. An instance of erosion.
1710. T. Fuller, Pharm. Extemp., 133. It [i.e., the Electuary] is very profitable against … erosions of the Mouth.
1725. Bradley, Fam. Dict., Ulcer, a Solution of Continuity made by an Erosion of the soft Parts.
1744. Berkeley, Siris, § 21. 11. Ulcerous erosions of the inward parts.
1880. Kinglake, Crimea, VI. viii. 184. Scurvy, disclosed by the tumours, the erosions of the gums, [etc.].
2. transf. and fig. Also concr.
1804. W. Taylor, in Ann. Rev., II. 352. The expenders of rents are the most unproductive and useless class of citizens; their income is a fairer object of erosion, than that of the industrious … classes.
1817. H. T. Colebrooke, Algebra, 311. The erosion being subtracted from both diameters [etc.].
1889. Sat. Rev., 23 March, 331/1. About twenty per cent. of the Government majority has disappeared by the natural erosion of bye-elections.
3. attrib. Erosion Theory: the theory that regards the contour of the land as due to superficial denudation rather than to subterranean agencies.
1879. Le Conte, Elem. Geol., 251. Erosion inequalities, once commenced, tend to increase.
