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stratum|ˈstrɑːtəm, ˈstreɪtəm|
Pl. strata |ˈstrɑːtə, ˈstreɪtə|; 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.
1599A. M. tr. 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. 1677Plot Oxfordsh. 249 [He] first laid at the bottom green Black-thorn bushes, and on them a stratum of large round stones. 1699Evelyn 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. 1799Phil. 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. 1800tr. Lagrange's Chem. II. 338 Scrape off..the stratum of verdigrise which covers each side of the plate. 1816T. L. Peacock Headlong Hall viii, Covering the whole with a stratum of turf. 1834J. 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. 1846J. 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. 1851Nichol Archit. Heav. 22 In the midst of a stratum or bed of stars. 1860Tyndall Glac. i. xviii. 132 The blue gleams which issued from the broken or perforated stratum of new snow. 1867Baker Nile Trib. vi. (1872) 79 It had been entirely denuded of the loam that had formed the upper stratum.
b. pl. strata.
a1700Ken Hymnotheo Poet. Wks. 1721 III. 46 Thus of each Age..The Strata there of Graves distinct remain. 1777Robertson 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. 1807T. 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. 1837Barham 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.
1735Dyche & Pardon Dict., Strata, a Layer or Bed of different Soil or Matter. 1766J. Bartram Jrnl. 9 Jan. 29 A high bluff of sand..under which was a strata four foot thick, of a brownish soft sand stone. 1768Hamilton 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 dissappears.
a. sing.
1699J. Brewer in Phil. Trans. XXII. 485 This Stratum of green Sand and Oyster-shells is..nigh 2 foot deep. 1709T. Robinson Nat. Hist. Westmorld. & Cumb. v. 27 Flints..make up no particular Stratum of this Earth, but are a sort of Mundick. 1772Pennant Tours Scot. (1774) 267 This whole stratum lies in an inclined position. 1804J. Barrow Trav. S. Africa II. 82 In the same stratum..I discovered several large masses of pyramidal crystals of quartz. 1830Lyell 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. 1863Dana 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. 1872Jenkinson 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.
1671H. O. tr. Steno's Prodr. Diss. Solids 37 To the Sediments of Fluids do belong the Strata or Beds of the Earth. 1695Woodward 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. 1706Phillips (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. 1730–46Thomson Autumn 1359 The mineral strata there, Thrust blooming thence the vegetable world. 1738T. 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. 1784Cowper Task iii. 151 Some drill and bore The solid earth, and from the strata there Extract a register by which [etc.]. 1842Penny 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. 1847Tennyson Princess iii. 154 That afternoon the Princess rode to take The dip of certain strata to the North. 1875Dawson Dawn of Life ii. 9 The..Laurentian strata..are seen to underlie..the Silurian beds. 1877Huxley Physiogr. ii. 24 The successive layers of rock, or as they are technically called strata.
c. pl. stratums. (Not in scientific use.)
1843Mr. & A. M. 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.
1796H. Hunter tr. St. Pierre's Study Nat. (1799) I. 38 That vast stratum of frozen air which surrounds our Globe, about a league above the surface. 1834M. Somerville Connex. Phys. Sci. §xiii. (1849) 113 Sir James Ross, who found a stratum of constant temperature in the ocean at a depth depending on the latitude. 1842Grove Lect. Progr. Phys. Sci. 18 No action is perceptible in the intervening stratum of liquid. 1850Rankine Misc. Sci. Papers (1881) 22 A portion of a spherical stratum of atmosphere surrounding an atomic centre. 1877Huxley Physiogr. vi. 84 The carbonic acid..would tend to settle down in a stratum near the ground.
b. pl. strata.
1787Crit. Rev. LXIV. 302 It was found that the change really arose from the drier air above, mixing with the inferior strata. 1812–16Playfair 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. 1854Tomlinson tr. Arago's Astron. 163 But gases being extremely compressible, the lower strata..are necessarily more compressed. 1858Jenyns 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.
1846G. E. Day tr. 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. 1866Treas. Bot. 1102/2 Stratum, a layer of tissue. 1884Bower & Scott De Bary's Phaner. 554 The cells of the endodermis..often form the outermost stratum of the cork-layer. 1899Allbutt'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.
1741A. Monro Anat. (ed. 3) 3 The..Strata or Layers, of which the Periosteum is composed. 1860Laycock Mind & Brain II. 359 Under certain circumstances the [ganglionic] cells are arranged in layers or strata. 1884Bower & 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.)
1856T. 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, as social stratum; and the like.
a. sing.
1807G. 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. 1850Carlyle Latter-d. Pamph. iii. 39 From the lowest and broadest stratum of Society..there was born,..a Robert Burns. 1862Stanley Jew. Ch. (1877) I. xix. 369 In modern times they have practically been drawn from one stratum of society. 1870Max Müller Sci. Relig. (1873) 318 Odin belongs to the same stratum of mythological thought as Dyaus in India. 1877C. M. 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. 1886T. H. S. Escott in P. Bailey Leisure & Class in Victorian England (1978) iii. 58 A social movement..is now steadily progressing on a lower social stratum. 1902L. Stephen Stud. Biogr. IV. vii. 261 The habit of reading spread to a lower social stratum. 1914Blackw. Mag. Oct. 505/2 He sprang from that stratum of the middle class..which owes its immediate fortunes to commercial enterprise. 1927P. Sorokin Social Mobility 141 There has never existed a society in which vertical social mobility has been absolutely free and the transition from one social stratum to another has had no resistance. 1973E. Berckman Victorian Album 50 This murder..must have been in too drab a social stratum..to attract even contemporary attention.
b. pl. strata.
1850Carlyle Latter-d. Pamph. iii. 38 In the lowest broad strata of the population..are produced men of every kind of genius. 1867A. Barry Sir C. Barry ii. 43 The superimposed strata of Greek, Roman, Saracenic and Gothic architecture. 1876Birch Monum. Hist. Egypt 15 Leaving as open questions the contemporaneity or sequence of the dynasties, but recognising them as representing strata of time. 1890Blackie 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. 1890W. James Princ. Psychol. I. iv. 121 Habit..keeps different social strata from mixing. 1913Sir 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. 1937R. H. Lowie Hist. Ethnological Theory vi. 57 It is hard to understand how Morgan could have missed the social strata of the caste-ridden Oceanians. 1968G. D. Mitchell Dict. Sociol. 182 In theory social strata are made up of individuals and families.
c. Statistics. Each of the groups into which a population is divided in the technique of stratified sampling.
1920A. L. Bowley Elements of Statistics (ed. 4) ii. iv. 332 It may happen..that the universe consists of different regions or strata in which the chances are different, and the question arises whether we should proceed at random.., or..partially arrange the choice so as to take the same proportion out of each region or stratum. 1952A. Hald Statistical Theory with Engin. Applications xvii. 495 In sampling investigations of industrial products stratified sampling is often useful. For example, when a lot is being loaded a random sample of items may be taken from every truckload, the truckloads being the strata. 1960Jrnl. Amer. Statistical Assoc. LV. 105 If the sample is allocated to the strata in proportion to the number of elements in the strata, it is virtually certain that the stratified sample estimate will have a smaller variance than a random sample of the same size. 1980Hawkins & Weber Statistical Analysis xi. 295 Stratified sampling is appropriate only if the variable of interest is relatively homogeneous within strata and heterogeneous among strata.
¶d. The form strata used as sing., with pl. stratas.
1937Times Lit. Suppl. 27 Nov. 910/2 He marries a penniless girl of a lower social strata than himself. 1946M. Peake Titus Groan 159 The mixture of cunning and honesty which he did not yet perceive to be a still deeper strata of Steerpike's cleverness. Ibid. 177 The abstract language with which they communicated their dizzy stratas of conjecture. 1971Timber Trades Jrnl. 14 Aug. 20/2 The era of the family business is now a complex structure of top, middle and lower stratas. 1980Good Housekeeping Nov. 181/4 After this comes a strata of accessories.
7. a. attrib. (in pl. form.)
1814Jameson in Mem. Wernerian Soc. II. 223 Two contiguous portions of rock, whether separated by strata-streams or not. 1839Ure 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. 1842Selby Brit. Forest Trees 351 The strata-like form the branches naturally assume. 1955T. H. Pear Eng. Social Differences i. 23 Within the wholesale trade there are interesting strata-differences. 1962Conveyancing (Strata Titles) Act in Statutes of New S. Wales 1961 129 ‘Strata plan’ means a plan which..shows the whole or any part of the land comprised therein as being divided into two or more strata, whether or not any such stratum is divided into two or more lots. 1977[see b below]. 1982Polit. Sci. Q. XCVII. 482 The manipulation of ethnicity or of strata-local forces.
b. (in sing. form.)
1955T. H. Pear Eng. Social Differences vi. 144 Neighbouring families for whom class-consciousness..was usually submerged below stratum-consciousness. 1977Dædalus Fall 73 Country-wide strata consciousness and a less pronounced stratum formation of ethnic, religious, or regional elements.
c. Special Combs.: strata-bound a., confined to a single stratum or group of strata; strata title Austral. and N.Z., the freehold or leasehold of or title to a stratum or storey (or more than one) of a building.
1962Econ. Geol. LVII. 272 It is..reasonable to expect that a majority of strata-bound ore fields will be readily explainable on explicit grounds of tectonic history. 1979Nature 15 Nov. 247/1 Uranium mineralisation, for the most part, is strata-bound and occurs in breccia matrix and vugs.
1962Statutes of New S. Wales 1961 128 (title) Conveyancing (strata titles) act. 1977Courier-Mail (Brisbane) 7 Apr. 17/2 Many strata title (home units) property owners risk serious financial loss because of inadequate legal insurance on their units. 1977N.Z. Herald 5 Jan. 2–16/2 (Advt.), Home unit, Avondale, as new, strata title, 2 brms, internal garage. |