Pl. strata; 9 rarely stratums. [a. mod.L. use of L. strātum, lit. something spread or laid down (in classical use with the senses ‘bed-cover,’ ‘horse-cloth,’ ‘pavement’), neut. pa. pple. of sternĕre to throw down, lay prostrate, spread out. Cf. F. strate fem. (1865 in Littré).]
1. gen. A quantity of a substance or material spread over a nearly horizontal surface to a more or less uniform thickness; a layer or coat; esp. one of two or more parallel layers or coats successively superposed one upon another.
The mod.L. phrase stratum super stratum (cf. quot. 1699) was often used in Eng. context by writers of the 17th c.: see e.g., quot. 1617 s.v. STRATIFICATION 1.
a. sing.
1599. A. M., trans. Gabelhouer’s Bk. Physicke, 54/1. Take a Copper basen,… insparge on the bottome therof a stratum of sault, and on that sault a row of mature Strawberryes.
1677. Plot, Oxfordsh., 249. [He] first laid at the bottom green Black-thorn bushes, and on them a stratum of large round stones.
1699. Evelyn, Acetaria, App. P 4. Cover the Bottom of the Jar with some Dill, an Handful of Bay-Salt, &c. and then a Bed of Nuts; and so stratum upon stratum as above.
1799. Phil. Trans., LXXXIX. 154. The stratum of soil, sixteen feet thick, placed above the decayed trees, seems to remove the epoch of their sinking and destruction, far beyond the reach of any historical knowledge.
1800. trans. Lagrange’s Chem., II. 338. Scrape off … the stratum of verdigrise which covers each side of the plate.
1816. T. L. Peacock, Headlong Hall, viii. Covering the whole with a stratum of turf.
1834. J. Dalton, Meteorol. Observ. (ed. 2), App. 197. The thickness of a stratum of clouds … is also variable from a few yards to three or four hundred or more.
1846. J. Baxter’s Libr. Pract. Agric. (ed. 4), I. 313. To prevent the attacks of slugs and worms, some cultivators recommend a stratum of lime … to be placed at the bottom of the bed.
1851. Nichol, Archit. Heav., 22. In the midst of a stratum or bed of stars.
1860. Tyndall, Glac., I. xviii. 132. The blue gleams which issued from the broken or perforated stratum of new snow.
1867. S. W. Baker, Nile Trib., vi. (1872), 79. It had been entirely denuded of the loam that had formed the upper stratum.
b. pl. strata.
a. 1700. Ken, Hymnotheo, Poet. Wks. 1721, III. 46. Thus of each Age … The Strata there of Graves distinct remain.
1777. Robertson, Hist. Amer., x. Notes, Wks. 1851, VI. 301. According to M. de Condamine, there were regular strata of building in some parts of Atun-Cannar, which he remarks as singular.
1807. T. Thomson, Chem. (ed. 3), II. 418. Thus there were three strata of liquids in the vessel: the acid lowermost, and the alcohol uppermost, separated from each other by the water.
1837. Barham, Ingol. Leg., Spectre of Tappington. Rescued from the grave in which they [his breeches] had been buried, like the strata of a Christmas pie.
¶ c. The form strata used as sing., with pl. stratas. Obs.
1735. Dyche & Pardon, Dict., Strata, a Layer or Bed of different Soil or Matter.
1766. J. Bartram, Jrnl., 9 Jan., 29. A high bluff of sand … under which was a strata four foot thick, of a brownish soft sand stone.
1768. Hamilton, Vesuvius, in Phil. Trans., LIX. 20. The soil consists of stratas of lavas, ashes, pumice, and now-and-then a thin stratum of good earth.
2. A bed of sedimentary rock, usually consisting of a series of ‘layers’ or ‘laminæ’ of the same kind, representing continuous periods of deposition.
The precise application of the term has varied, some geologists having used it as equivalent to ‘layer’ or ‘lamina.’ In the collective plural strata, which is much the most frequent use, the distinction between the different uses commonly disappears.
a. sing.
1699. J. Brewer, in Phil. Trans., XXII. 485. This Stratum of green Sand and Oyster-shells is … nigh 2 foot deep.
1709. T. Robinson, Nat. Hist. Westm. & Cumberl., v. 27. Flints … make up no particular Stratum of this Earth, but are a sort of Mundick.
1772. Pennant, Tours Scot. (1774), 267. This whole stratum lies in an inclined position.
1804. J. Barrow, Trav. S. Africa, II. 82. In the same stratum … I discovered several large masses of pyramidal crystals of quartz.
1830. Lyell, Princ. Geol., I. 203. One stratum, composed of many layers, is of a compact nature and fifteen feet thick; it serves as an excellent building stone.
1863. Dana, Man. Geol., 91. A stratum, the collection of layers of one kind which form a rock as it lies between beds of other kinds…. A stratum may consist of many layers.
1872. Jenkinson, Engl. Lake Distr. (1879), 36. When ascending from Long Sleddale the stratum of limestone is observed in the gill on the left.
b. pl. strata.
1671. H. O., trans. Steno’s Prodr. Diss. Solids, 37. To the Sediments of Fluids do belong the Strata or Beds of the Earth.
1695. Woodward, Nat. Hist. Earth (1702), 29. Shells … fell to the bottom at the same time that the Chalky Particles did, and so were entombed in the Strata of Chalk.
1706. Phillips (ed. Kersey), Strata … the Layers or Beds of different kind of Earthy Matter, that lie one over another without any regular Order, in the most part of the whole Globe of Earth.
1730–46. Thomson, Autumn, 1359. The mineral strata there, Thrust blooming thence the vegetable world.
1738. T. Story, in Mem. J. Logan (1851), 155. Scarborough … at whose high cliffs and the great varieties of strata therein and their present positions, I further learned and was confirmed in some things.
1784. Cowper, Task, III. 151. Some drill and bore The solid earth, and from the strata there Extract a register by which [etc.].
1842. Penny Cycl., XXIII. 105/2. In Geology, both the separately deposited layers of rock, and the rocks formed of these similar layers, accumulated together, have received the name of strata.
1847. Tennyson, Princess, iii. 154. That afternoon the Princess rode to take The dip of certain strata to the North.
1875. J. W. Dawson, Dawn of Life, ii. 9. The … Laurentian strata … are seen to underlie … the Silurian beds.
1877. Huxley, Physiogr., ii. 24. The successive layers of rock, or as they are technically called strata.
c. pl. stratums. (Not in scientific use )
1843. Mr. & Mrs. S. C. Hall, Ireland, III. 170. The black irregular rocks, the stratums of many colours and the débris of a sloping bank.
3. A region of the atmosphere, of the sea, or of a quantity of fluid, assumed for purposes of calculation as bounded by horizontal planes.
a. sing.
1796. H. Hunter, trans. St.-Pierre’s Study Nat. (1799), I. 38. That vast stratum of frozen air which surrounds our Globe, about a league above the surface.
1834. Mrs. Somerville, Connex. Phys. Sci., § xiii. (1847), 113. Sir James Ross, who found a stratum of constant temperature in the ocean at a depth depending on the latitude.
1842. Grove, Lect. Progr. Phys. Sci., 18. No action is perceptible in the intervening stratum of liquid.
1850. Rankine, Misc. Sci. Papers (1881), 22. A portion of a spherical stratum of atmosphere surrounding an atomic centre.
1877. Huxley, Physiogr., vi. 84. The carbonic acid … would tend to settle down in a stratum near the ground.
b. pl. strata.
1787. Crit. Rev., LXIV. 302. It was found that the change really arose from the drier air above, mixing with the inferior strata.
1812–6. Playfair, Nat. Phil. (1819), I. 245. If, therefore, the heights from the surface be taken increasing in arithmetical progression, the densities of the strata of air will decrease in geometrical progression.
1854. Tomlinson, trans. Arago’s Astron., 163. But gases being extremely compressible, the lower strata … are necessarily more compressed.
1858. Jenyns, Observ. Meteorol., 204. The temperature of the lower strata of the air.
4. Biol. etc. One of a number of layers composing an animal or vegetable tissue.
a. sing.
1846. G. E. Day, trans. Simon’s Anim. Chem., II. 99. If a normal stratum of epithelium is no longer formed,… the changes impressed on the fluid must be different from those which it would undergo during the ordinary secretion of healthy mucus.
1866. Treas. Bot., 1102/2. Stratum, a layer of tissue.
1884. Bower & Scott, De Bary’s Phaner., 554. The cells of the endodermis … often form the outermost stratum of the cork-layer.
1899. Allbutt’s Syst. Med., VIII. 600. The collagenous tissue of the uppermost stratum of the cutis may now undergo a distinct sclerotic change.
b. pl. strata.
1741. A. Monro, Anat. (ed. 3), 3. The … Strata or Layers, of which the Periosteum is composed.
1860. Laycock, Mind & Brain, II. 359. Under certain circumstances the [ganglionic] cells are arranged in layers or strata.
1884. Bower & Scott, De Bary’s Phaner., 83. The strata or crusts are superposed on the cuticle in the form of a continuous membrane.
5. Electr. (Cf. STRATIFICATION 2 d.)
1856. T. R. Robinson, in Proc. R. Irish Acad., VI. 428. The meniscoid strata were at first very distinct, but faded away in a few seconds.
6. fig. in various applications (chiefly after sense 2): A portion of a body of institutions, beliefs, etc., proceeding from one historical period or representing one stage of development; a level or grade in social position or culture; the part of a population belonging to a particular level in station or education; and the like. a. sing.
1807. G. Chalmers, Caledonia, I. 229, note. The first stratum of names on the map of North-Britain is Cambro-British;… the second stratum … superinduced on the former, was the Gaelic.
1850. Carlyle, Latter-day Pamph., iii. 39. From the lowest and broadest stratum of Society … there was born,… a Robert Burns.
1862. Stanley, Jew. Ch. (1877), I. xix. 369. In modern times they have practically been drawn from one stratum of society.
1870. Max Müller, Sci. Relig. (1873), 318. Odin belongs to the same stratum of mythological thought as Dyaus in India.
1877. Miss Yonge, Cameos, I. ii. 17. The Caroline race were Franks,… a mixture of Roman and Gallic, with only an upper stratum of the true Frank.
1902. L. Stephen, Stud. Biogr., IV. vii. 261. The habit of reading spread to a lower social stratum.
1914. Blackw. Mag., Oct., 505/2. He sprang from that stratum of the middle class … which owes its immediate fortunes to commercial enterprise.
b. pl. strata.
1850. Carlyle, Latter-day Pamph., iii. 38. In the lowest broad strata of the population … are produced men of every kind of genius.
1867. A. Barry, Sir C. Barry, ii. 43. The superimposed strata of Greek, Roman, Saracenic and Gothic architecture.
1876. Birch, Monum. Hist. Egypt, 15. Leaving as open questions the contemporanity or sequence of the dynasties, but recognising them as representing strata of time.
1890. Blackie, Ess. Mor. & Soc. Int., 298. In fact a large proportion of the upper strata of English is merely Latin and Greek in a very thin disguise.
1913. Sir T. Barlow, in Times, 7 Aug., 8/2. The … study of small variations in the ordinary diets of adults and children … in different social strata and in different countries.
7. attrib. (in pl. form.) ? Obs.
1814. Jameson, in Mem. Wernerian Soc., II. 223. Two contiguous portions of rock, whether separated by strata-streams or not.
1839. Ure, Dict. Arts, 748. The flat veins, or strata veins, seem to be nothing else than expansions of the matter of the vein between the planes of the strata.
1842. Selby, Brit. Forest Trees, 351. The strata-like form the branches naturally assume.
