DYKE 



2749 



DYNAMICS 



be applied to wool. They are used 

 in large quantities, especially sul- 

 phide blacks. At present a good 

 range of sulphide dyestuffs is not 

 available, a bright red being absent. 

 These colours are not soluble in 

 water, and have to be dissolved with 

 the aid of sodium sulphide. On cot- 

 ton they produce shades of extreme 

 fastness to washing,vary in fastness 

 to light, but are poor to bleaching. 



VAT DYESTUFFS. This is now an 

 important class of colours, al- 

 though indigo was the only one 

 known up to comparatively recent 

 times. They are all insoluble in 

 water, and are made soluble by a 

 process of reduction, whereby they 

 become soluble in an alkaline bath. 

 Only indigo and its derivatives are 

 used for wool dyeing on account 

 of the strongly alkaline bath re- 

 quired for the other classes (Indan- 

 threnes, Algoles, etc.). All are used 

 for cotton dyeing, and the class 

 contains some of the fastest colours 

 existing. They are used for cur- 

 tains, etc., where great fastness to 

 light is required. 



INSOLUBLE COLOURS. To this 

 group belong aniline black, Para 

 red, etc. Aniline black is formed 

 on the cotton fibre by the oxida- 

 tion of aniline, previously applied 

 to the fibre in the form of a soluble 

 salt. It is a very fast black, and 

 recognized as a standard for cotton 

 goods, but it has been replaced to a 

 considerable extent by sulphide 

 blacks, which are easier of applica- 

 tion. Para red is obtained by actu- 

 ally forming an insoluble colour 

 on the fibre by the successive com- 

 bination of its components. 



Before 1914, 90 p.c. of the total 

 quantity of artificial dyestuffs was 

 produced in Germany. After 

 1918, however, large factories were 

 erected in Great Britain, America, 

 and France. 



Bibliography. Dictionary of Dyes, 

 Mordants and other Compounds, 

 C. Rawson and others, 1901 ; A 

 Treatise on Colour Manufacture, G. 

 Zerr and R. Riibencamp, Eng. trans. 

 C. Mayer, 1908 ; A Manual of 

 Dyeing, E. Knecht and others, 2nd 

 ed. 1910. 



Dyke OR DIKE. Defensive earth- 

 work or its adjacent ditch, especi- 

 ally in early Britain. Dykes may te 

 promontory forts, or protective 

 works as used in Holland, and in 

 Great Britain as fenland causeways. 

 Some were made or re -used for na- 

 tional or tribal boundaries. Red 

 Earl's Ditch, along the Malvern 

 Hills, was feudal. The greatest, 

 Wansdyke, 80 m. long, from the 

 Severn to Inkpen Beacon, Berks, 

 was pre-Roman. Black Dyke, from 

 Richmond, Yorks, across the Ro- 

 man Wall to Peel Fell, Northum- 

 berland, continues as the Catrail 

 for 48 m. to Galashiels, Selkirk- 



shire. Roman Dyke, Rushmore, 

 Wilts, was Romano-British. There 

 are 25 in Dorset, and, perhaps, 50 

 elsewhere, some being of Common- 

 wealth date. (See Devil's Dyke ; 

 Orim's Dyke. ) 



In geology, dykes are wall-like 

 masses of rock formed in vertical or 

 highly inclined fissures in older for- 

 mations. The name arose from 

 their resemblance, when the softer 

 enveloping rocks have been wea- 

 thered away, to the structures made 

 by man ; in W. Scotland they are 

 actually utilised as enclosures. 



The most typical dykes com- 

 prise basalts and similar rocks in- 

 truded by igneous action. They 

 often form ribs spreading radially 

 from volcanic craters. When the 

 molten lava has receded from the 

 inner part before cooling, hollow 

 dykes result. A vast system, cover- 

 ing 40,000 sq. m. from Orkney to 

 Yorkshire, comprises dykes vary- 

 ing from a few inches to 70 ft. in 

 breadth, and up to 100 m. long, 

 notable examples being the Cleve- 

 land and Acklington dykes. The 

 long line of fissure -eruptions occur- 

 ring in Iceland in 1783 formed a 

 new subterranean dyke 20 m. long. 



Sedimentary dykes have been 

 formed in all geological ages, such 

 as the pre-Cambrian sandstone 

 dykes at Ben Slioch, Ross -shire, and 

 those of limestone near San Fran- 

 cisco. These are sometimes due to 

 the filling-up of fissures caused by 

 submarine earthquakes. 



Dykes, JAMES OSWALD (1835- 

 1912). British theologian. Born 

 at Port Glasgow, Aug. 14, 1835, 

 and educated at 

 Dumfries Acad- 

 emy, Edin- 

 burgh Univer- 

 sity, and New 

 College, Heidel- 

 berg, and Er- 

 langen, he was 

 ordained at East 

 Kilbride, 1859. 

 Colleague of Dr. James Oswald Dykes, 

 Candlish (q.v.), British theologian 

 at Free S. W 



George's, Edinburgh, 1861-64, he 

 resigned through ill-health. After 

 spending three years in Melbourne, 

 Australia, he was minister of Regent 

 Square Presbyterian Church, Lon- 

 don, 1869-88 : and principal, 1888 

 -1907, of the English Presbyterian 

 College, Queen Square, London, 

 afterwards removed to Cambridge, 

 and known as Westminster College. 

 His works include The Beatitudes 

 of the Kingdom, 1872 ; The Gospel 

 According to S. Paul ; studies in 

 the first 8 chapters of his Epistle 

 to the Romans, 1888; and The 

 Divine Worker in Creation and Pro- 

 vidence, 1909. He died Jan. 1,1912. 



Dykes, JOHN BACCHUS (1823- 

 76). British musician and church- 



man. Born at Hull, Mar. 10, 1823, 

 he studied music at Cambridge and 

 became a clergyman. In 1849 he 

 was appointed precentor of Dur- 

 ham Cathedral and vicar of S. 

 Oswald's, Durham. He was one of 

 the editors of Hymns Ancient and 

 Modern, and composed a large 

 amount of church music, including 

 many hymn tunes ; some of these 

 Nearer my God to Thee, and 

 Jesu, Lover of my Soul have 

 attained immense popularity. He 

 died Jan. 22, 1876. See Life and 

 Letters, ed. J. T. Fowler, 1897. 



Dykh-Tau. One of the heights 

 of the Caucasus (17,000 ft.) in the 

 highest part of the range. 



Dymoke. English family in 

 which the ancient office of king's 

 champion is hereditary. The origin 

 of the Dymokes is variously traced 

 to the village of Dymoke, in Glou- 

 cestershire, and to a place of that 

 name on the Welsh border. Sir 

 John Dymoke (d. 1381) was cham- 

 pion at the coronation of Richard 

 II, the earliest recorded perform- 

 ance of the ceremony, and based 

 his right on his ownership by grand 

 serjeanty of the manor of Scri- 

 velsby, in Lincolnshire. Henry 

 Dymoke (d. 1865) was champion 

 at George IV's coronation, after 

 which the ceremony was dis- 

 continued, though the office re- 

 mained. In the reign of George V 

 the champion was Frank Seaman 

 Dymoke. See Champion. 



Dynamical Equivalent of 

 Heat. Whenever work is con- 

 verted into heat, or vice versa, 

 there is an unchanging relation 

 between the work done and the 

 heat produced or lost. The quan- 

 tity of work exerted to produce the 

 unit quantity of heat energy is 

 called the dynamical equivalent of 

 heat. The first to determine this 

 equivalent was Joule, whose first 

 method consisted in measuring the 

 heat developed when a known 

 amount of work was done in stir- 

 ring water. It has been found that 

 the energy converted into sufficient 

 heat to raise the temperature of one 

 gramme of water one degree (from 

 14'5 to 15'5) is 4-182 centigrade 

 times 10,000,000 ergs, where the erg 

 is the unit of work. See Heat; 

 Thermodynamics. 



Dynamics (Gr. dynamis, power). 

 Branch of the science of mechanics 

 which investigates the action of 

 fores. It therefore includes the 

 investigation of the conditions of 

 bodies which are in a state of 

 equilibrium owing to the forces 

 acting upon them, although this 

 special branch of the science is 

 often referred to as " statics." 

 The investigations depend ulti- 

 mately on the Newtonian Laws 

 of Motion. The various depart- 



