EROSION 



Erosion (Lat. erosio, eating 

 away). The wearing down of the 

 earth's surface through the action 

 of the atmosphere, rain, rivers, ice, 

 and the sea and its tides. Atmo- 

 spheric erosion is either chemical 

 or mechanical. Wind transports 

 particles and polishes surfaces over 

 which they are carried, e.g. in 

 deserts. Sudden changes of tem- 

 perature cause particles of rock 

 to split off, subsequently to be 

 removed by wind or water. Atmo- 

 sphere acts chemically through 

 rainfall, in causing decomposition 

 of rocks. Disintegration of rocks 

 being thus effected, the products 

 are afterwards removed by running 

 water, in most cases the water erod- 

 ing the boundaries of its course by 

 abrasive action of materials carried. 



Erosion beneath the surface of 

 the ground is chiefly chemical, 

 and often results in formation of 

 caves and caverns, especially in 

 limestone districts. Glacial erosion 

 takes place over large areas and on 

 an extensive scale, ice being, under 

 certain conditions, a powerful 

 scouring agent. Marine erosion is 

 in continuous progress along coasts, 

 the sea often using debris broken 

 from cliffs by waves as battering- 

 rams for further destruction. The 

 burrowing of animals, e.g. worms, 

 and penetration of roots of plants 

 assist also in disintegration of land 

 surfaces. The general result of all 

 erosion is to lower the level of land. 

 See Coast ; Glacier ; River. 



Erotic Literature (Gr. erotikos, 

 amatory). Literature inspired by 

 the theme of love. The name is 

 generally applied to poetry, and 

 latterly more especially to poetry 

 of a warmly impassioned character. 

 The classical erotic poets include 

 Anacreon, Callimachus, Sappho, 

 and Theocritus among the Greeks ; 

 and Catullus, Horace, Ovid, and 

 Tibullus among the Latins. The 

 troubadours of the Middle Ages 

 carried on the erotic tradition in 

 France, and at the Renaissance this 

 form of literature had a revival on 

 the continent of Europe. In Eng- 

 lish literature it reached a high 

 level in the lyrical work of poets of 

 the 17th century, such as Donne, 

 Cowley, Herrick, Waller, Lovelace, 

 and Suckling. In the 19th century, 

 more especially in the latter half, it 

 had a recrudescence in the poems 

 of Rossetti and Swinburne, and in 

 France in the writings of Baude- 

 laire and others. 



Er Ram. Village of Palestine. 

 It is situated on a hill on the Jeru- 

 salem -Nablus road. Identified as 

 the ancient Ramah (q.v.) of Ben- 

 jamin (1 Kings xv, 17), it formed a 

 kind of frontier castle between the 

 N. and S. kingdoms of Palestine, 

 and was repeopled after the return 



2966 



from captivity. The modern vil- 

 lage was captured by Allenby, Dec. 

 28, 1917, in the advance following 

 the capture of Jerusalem. , See 

 Palestine, Conquest of. 



Erratics (Lat. errare, to wan- 

 der). In geology, portions of rock 

 of varying size which have been 

 moved from their original home by 

 natural agencies. They commonly 

 consist of rock-fragments torn 

 away by glaciers, and often bear 

 scratches resulting from move- 

 ment under great pressure. They 

 occur in great profusion in glacial 

 boulder-clays, and are often spread 

 over high levels by glacial tor- 

 rents. See Glacier ; Rock. 



Errigal OB ABIGAL. Mountain 

 of Donegal, Ireland, the highest 

 point in Ulster. It is 5 m. S.E. of 

 Gweedore and is 2,460 ft. high. 



Enroll, EARL OF. Scottish title 

 borne since 1452 by the family 

 of Hay. William Hay, hereditary 

 constable o f 

 Scotland, a n 

 honour given 

 in 1315 to his 

 forefather, Sir 

 Gilbert, was 

 made an earl 

 in 1452. The 

 first earls 

 were not very 

 prominent, but 

 Francis, the 

 9th earl, was 

 active in the 16th century, being 

 constantly in rebellion against 

 James VI. He was then a Roman 

 Catholic, and in league with Spain : 

 in 1594 he led a small rising, after 

 which his residence, Slains Castle, 

 was destroyed. Later he became a 

 Protestant. 



A dispute as to whether Erroll 

 or the earl marischal was the right- 

 ful constable was decided in favour 

 of the former, and so the earls take 

 precedence in Scotland just after 

 the royal family. When the 13th 

 earl died unmarried his sister suc- 

 ceeded to the title. The great- 

 nephew who followed was a son of 

 the earl of Kilmarnock who was 

 executed for his share in the rising 

 of 1745, but this did not affect his 

 earldom, and from him the later 

 earls are descended. The 18th earl, 

 lord steward of the household, was 

 made a peer of the United King- 

 dom as Baron Kilmarnock in 1831, 

 and in 1891 his grandson, Charles 

 Gore Hay (b. 1852), became the 

 20th earl. The earl's estates are 

 in Aberdeenshire, where is his seat, 

 Slains Castle. His eldest son is 

 - called Lord Kilmarnock. 



Erromanga. One of the S. 

 group of the New Hebrides. It 

 measures 30 m. long by 20 wide. 

 The chief anchorage is Dillon's 

 Bay ; the chief product, copra. 



20th Earl of Erroll, 

 British soldier 



Lafayette 



Here John Williams, the mission- 

 ary, was killed and eaten in 1839, 

 since when most of the natives have 

 been Christianised. Est. pop. 2,500. 



Error. False idea which is re- 

 garded as true. Errors are due to 

 an appearance of truth, which de- 

 ceives the subject. When referring 

 to the logical form of the judge- 

 ment, they are formal, and contra- 

 dict the laws of thought ; when to 

 its content they are material, and 

 contradict the facts. 



There are two important classes 

 of error : those which are of so 

 little consequence that they may be 

 neglected, and those which are in- 

 evitable, but must be allowed for. 

 Error in Mechanics 



Most munition workers were in- 

 troduced to the necessity for ex- 

 treme accuracy of measurement in 

 dealing with delicate machinery, 

 and brought to realize that errors 

 of small magnitude but important 

 consequences were unavoidable. 

 They learnt something of the deli- 

 cacy of modern scientific measure- 

 ments, and, in many cases, found 

 that the instruments which they 

 used were subject to a constant 

 error, for which allowance had to 

 be made. No scientific investiga- 

 tor uses an instrument for precise 

 measurement without first finding 

 the constant error to which it is 

 subject. Consequently a piece of 

 metal reputed to be 31 ins. in length 

 is almost certainly not precisely 31 

 ins. If the ruler used is accurately 

 graduated to tenths of an inch the 

 possible error may be ^ in. too 

 much or too little ; this error is 

 solely due to the fact that the ruler 

 only shows tenths of an inch. It be- 

 comes a matter of importance to 

 investigate the character of such 

 errors, and statisticians have for- 

 mulated the " law of error," from 

 which the probable error in the 

 measurement can be calculated. 



It is found mathematically that 

 the likelihood that the actual error 

 will exceed the probable error is 

 small, there is only one chance in 

 six that the actual error will be 

 double, and one in 1,388 that it will 

 be five times the probable error. 

 Scientists, consequently, express 

 numerical results in the form 6'17 

 '02, which means that the mea- 

 sured value is probably 6*17, and 

 certainly not more than 6'19, nor 

 less than 6 '15, and, further, that 

 there is a very great probability 

 that the error is less than (V01, 

 although the potable erroris 0'02. 



Errors are sometimes conveni- 

 ently expressed as percentages, 

 e.g. 1 p.c. ; and when calcula- 

 tions are made with quantities, 

 each of them subject to a possible 

 error, the final result is subject 

 to a much larger error, e.g. if A, B, 



