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stratification|strætɪfɪˈkeɪʃən|
[ad. med.L. strātificātiōnem, n. of action f. strātificāre: see stratify v. and -fication. Cf. F. stratification (1656 in Hatz.-Darm.).]
1.
†a. The action of depositing something in layers; spec. (see quots.). Obs.
1617Woodall Surg. Mate (1639) 274 Stratification, or stratum superstratum well knowne to Chymists, and used in cementation, is strewing of corroding powder, or the like, upon plates of metall by course. Ibid. 266 Stratifigations [sic]. 1669tr. Benguinus' Tyroc. Chym. 25 Stratification is a corrosion by corrosive powders. It is thus made, [etc.]. 1669Rowland Schroder's Chym. Disp. i. xiv. 21 Stratification in Beguin comprehends the whole Art of Calcination, by which the Plates are made brittle, this they say is Cæmenting. 1704J. Harris Lex. Techn. I, Stratification, or stratum super stratum, as the Chymists call it, is putting different Matters Bed upon Bed, or one layer upon another, in a Crucible in order to Calcine a Metal or Mineral. 1787R. Watson Chem. Ess. V. 251 Copper combined with sulphur by stratification and cementation... æs ustum. 1815J. Smith Panorama Sci. & Art II. 301 Stratification, an operation in which bodies are placed alternately in layers, in order that they may act upon each other when heat is applied to them. 1882Encycl. Brit. XIV. 385/1 It was formerly the practice in England..to tan by the process of stratification, for which purpose a bed of bark is made..; upon this is laid the hide, then bark, then a hide, and so on.
b. The placing of seeds close together in layers between layers of moist sand, peat, or the like in order to preserve them or promote germination; also extended to the placing of seeds in such a medium other than in layers.
1914Moon & Brown Elem. of Forestry vi. 103 Commercial houses rarely practice stratification, because they have storehouses where moisture conditions are kept uniform. 1928Jrnl. Forestry XXVI. 775/2 Stratification of these seeds for one to four months previous to planting has been found to hasten greatly their germination. 1976H. L. Edlin Nat. Hist. Trees xiv. 181 The seeds of ash trees..and many other common genera..require stratification for sixteen months.
2. The formation, by natural process, of strata or layers one above the other; the fact or state of existing in the form of strata, stratified condition; also, the manner in which something is stratified.
a. Geol. The formation of strata in portions of the crust of the earth by successive deposits of sedimentary matter; the manner in which a portion of the crust of the earth is stratified.
1795J. Hutton Theory Earth ii. ix. II. 307 This summit is of solid granite, a mass in which there is no stratification. 1796Kirwan Elem. Min. (ed. 2) I. 420 A total absence of stratification near the crater. 1802Playfair Illustr. Huttonian Theory 500 Thus by the waste and subsequent stratification of the land the direction of gravity is continually altered. 1830Lyell Princ. Geol. I. 203 The planes of stratification are perfectly parallel. 1838Poe A. Gordon Pym xviii. Wks. 1865 IV. 146 The very rocks were novel in their mass, their color, and their stratification. 1851Richardson Geol. (1855) 135 There are three distinct forms of structure frequently present in rocks of this nature: stratification, joints, and slaty cleavage. 1878A. C. Ramsay Phys. Geog. iv. 38, I have shown how aqueous rocks may generally be known by their stratification.
b. concr. A stratum produced by this process.
1808W. Richardson in Phil. Trans. XCVIII. 220 Regular stratifications on the summits of hills and mountains, have been long a stumbling block to theorists. 1822J. Parkinson Outl. Oryctol. 267 The matrix of these fossils is evidently a portion of the same stratification which occurs at Pappenheim.
c. Biol. and Path. The thickening of a tissue by the deposition or growth of successive thin layers.
1875tr. De Bary in Jrnl. Bot. Oct. 301 In Chara fragilis,..this membrane shows a copious tender stratification after the carbonate of lime has been dissolved. 1876tr. Wagner's Gen. Pathol. 200 The form, color, and stratification of the impacted piece. 1880Bessey Bot. 32 During the increase of the cell-wall in thickness, an appearance of stratification arises in it. 1887T. W. Shore Elem. Biol. Vegetable 10 Observe..Stratification of the cuticle, i.e. the appearance of lines in it, parallel to the surface of the section. 1899J. Cagney tr. von Jaksch's Clin. Diagn. iv. (ed. 4) 115 In some diseases, as in abscess and gangrene of the lung there is marked stratification of its [i.e. the sputum's] parts.
d. Electr. The striated appearance assumed by an electric discharge passing through a highly rarefied gas.
1856T. R. Robinson in Proc. R. Irish Acad. VI. 429 When a Leyden jar (each coating about a foot) was connected with the terminals, the stratification was well seen in each direction of the current. 1858J. P. Gassiot in Phil. Trans. 1 The phenomenon of stratifications in the discharge in vacuo were subsequently observed in Paris by M. Ruhmkorff. 1866R. M. Ferguson Electr. (1870) 193 The cause of this stratification is as yet a matter of speculation.
e. transf. and fig. Chiefly with reference to the geological use, and spec. in Sociol., the formation and establishment of social or cultural levels resulting from differences in occupation and political, ethnic, or economic influence.
1860Maury Phys. Geog. (Low) xxii. §885 Let us, in imagination, divide these depths..into any number of stratifications or layers of equal thickness. 1862Burton Bk. Hunter (1863) 113 The library is the great intellectual stratification in which the literary investigator works. 1879Baring-Gould Germany I. 2 The stratification of the German classes, and of the aristocracy, is most peculiar. 1889A. Sidgwick in Jrnl. Educ. Feb. 117 That there is not a chance of saving much time by improved methods and proper stratification. 1910D. G. Hogarth in Encycl. Brit. I. 248/2 (Aegean Civiliz.), By exact observation of stratification, eight more periods have been distinguished by the explorer of Cnossus. 1927P. Sorokin Soc. Mobility ii. 13 Unstratified society..is a myth which has never been realized in the history of mankind... The forms and proportions of stratification vary, but its essence is permanent. 1944S. Putnam tr. da Cunha's Rebellion in Backlands ii. 117 It was natural that the deep-lying layers of our ethnic stratification should have cast up so extraordinary an anticlinal as Antonio Conselheiro. 1962Guardian 22 June 20/2 The so-called gulf between science and literature..led to no social stratification. 1981R. Fletcher Sociol. vii. 200 Specific interest groups and a changing ethnic composition are the elements most likely to be troublesome in..problems of social stratification.
f. The existence in a lake or other body of water of two or more distinct layers differing in temperature, density, or the like.
1898Amer. Naturalist XXXII. 26 It is in a condition of ‘inverse stratification’, as Forel calls it, when the colder water is above the warmer. 1935P. S. Welch Limnology iv. 51 Exceptional meteorological conditions may..prevent stratification completely. 1952Phil. Trans. R. Soc. B. CCXXXVI. 355 (heading) Water movements in lakes during summer stratification. 1972M. G. Gross Oceanography vii. 191 Well-developed density stratification of the open ocean inhibits strong vertical currents. 1973P. A. Colinvaux Introd. Ecol. xviii. 249 If a lake is highly productive, thermal stratification has some interesting consequences for the bottom water.
g. Variation in the richness of the fuel-air mixture during the period of its introduction into the cylinder of an internal-combustion engine.
1922H. R. Ricardo Internal-Combustion Engine I. v. 75 In order to increase the range of power as far as possible, every effort is made to encourage stratification. 1981Sci. Amer. May 45/1 The stratification also makes it possible to burn fuel-air mixtures so lean in fuel that they would not burn if the fuel were uniformly mixed with the air.
3. Statistics. The (usu. notional) division of a population into distinct groups from each of which a proportion of an overall sample may be taken.
1920A. L. Bowley Elements of Statistics (ed. 4) ii. iv. 336 The stratification of a universe of measurable objects is also treated by Mr. Yule. 1934Jrnl. R. Statistical Soc. XCVII. 608 This method of stratification..gives an improvement in precision. 1957Kendall & Buckland Dict. Statistical Terms 282 The process of stratification may be undertaken on a geographical basis, e.g. by dividing up the sampled area into sub-areas on a map. 1966Rep. Comm. Inquiry Univ. Oxf. II. 420 In drawing the sample stratification by college and subject was used to the greatest possible extent. 1967G. Wills in Wills & Yearsley Handbk. Management Technol. 187 This process of stratification..can only be carried out if you have details of the relevant population of shops by region, type, etc. 1977Lancet 28 May 1142/2 With stratification for hospital, age, and year of admission, the maximum-likelihood estimate of uniform risk ratio was 3·3.
4. attrib.
1884A. Geikie in Nature 13 Nov. 30/1 These thrust-planes..could not be distinguished from ordinary stratification-planes. |