D O L 



14 



DOM 



; ! 



13+5 



Male*, '. ; 



Females, , 



Total population in 1811 806* 



Do. in 1801, '_'!>W 



Increase since 1801, 115 



See Evans's Tonr through Xor/A Wale.-; ; and Evans's 

 Beauties of England and ll'n>r.\, \ol.xvii.p.915. (A 



DOLICHOS, a genus of plants of the class Diadel- 

 phia, and order Decandria. See BOTANY, p. 'J77. 



DOI.I.f )N1), JOHN, a celebrate<l optician, who has 

 immortalise<l his name bv the great discovery of the 

 achromatic telescope. He was born in Spitalfields, 

 London, on the 10th of June 1706, of French parents, 

 who had fled from Normandy in consequence of the 

 revocation of the edict of Nantes. In the early part of 

 his life, Mr Dollond wrought at the loom, but before 

 the age of I .">, he had acquired a taste for philosophical 

 and mathematical pursuits, and spent his leisure hours 

 in studying elementary works of science, and in the 

 construction of sun-dials and geometrical figures. In 

 this way he acquired a knowledge Of geometry and al- 

 gebra ; and though his opportunities for study were 

 diminished by an early marriage, and the cares of an 

 increasing family, yet his ardour for knowledge was un- 

 extinguished, and he contrived, by abridging his hours 

 of repose, to acquire a profound knowledge of optics 

 and astronomy. His attention was also directed to ana- 

 tomy and divinity; and he even found leisure to acquire 

 the \Mtln and Greek languages, in order that he might 

 apply himself more successfully to his favourite pur- 

 tlits. 



Mr Dollond, along with his son Mr Peter Dollond, 

 carried on for some time the business of manufacturers; 

 but the extensive information which the son had acqui- 

 red from his father's instructions, induced him to com- 

 mence optician. The success with which this plan was 

 attended, prompted his father to join him in his new pro- 

 fession, an event which happened in the year 1752. 



After acquiring a practical knowledge of optics, Mr 

 John Dollond directed his attention to the improvement 

 of the eye-glasses of refracting telescopes ; and he suc- 

 ceeded in producing an eye-piece of four glasses, and 

 sometime afterwards an eye-piece of five glasses, which 

 greatly surpassed those in common use. An account of 

 these eye-pieces was read before the Royal Society in 

 1 753, and afterwards published in the 48th volume of 

 their Transactions. 



The next effort of Mr Doflond, was an improvement 

 of the double image micrometer, or hcliometer, which 

 was invented by Savory and Bouguer. This improve- 

 ment consisted in using two semilenses instead of two 

 whole object glasses, and has already been fully descri- 

 bed in our article ASTRONOMY. See Vol. II. p. 734. 



Mr Dollond's attention was now turned to the im- 

 provement of the retracting telescope, and his labours 

 were crowned, by the invention of one of the finest in- 

 struments that has ever been constructed. The various 

 by which he was conducted to this splendid re- 

 sult, have already been fully detailed in our history of 

 the AC.HROMATIC TKLERCOPK, so that we must refer our 

 readers to that article for farther information. In ho- 

 nour of this invention, the Royal Society of London 

 presented Mr Dollond with Sir Godfrey Copley's medal. 

 This learned body also elected him a fellow of their So- 

 in 1761, and in the Fame year he was appointed 

 optician to his majesty. These honours, however, he 

 did not live long to enjoy. While reading Clairaut's the- 

 ory of the moon, with which he had been intensely oc- 



cupied for several hours, he was struck with apoplexy, 

 of which he died in a lew hour-, on the .'!P;!i nf Novem- 

 ber I 7<il . in the :V.th year of his age. Mr Dollond left 

 behind him two sen.-, ami three daughters ; and his bu- 

 siness was carried on by his sons and his nephew Mi- 

 George I luiTL/i'iis, who took the name of Dollond. 



Mr Dollond was a man highly respected in his moral 

 and religious character. " In his appearance," says l)r 

 Kelly, "he was grave, and the strong line- of his face 

 were marked with deep thought and reflection ; but in 

 his intercourse with his family and friends he v .1- cheer- 

 ful and affectionate ; and his language and sentiment - 

 are distinctly recollected, as always making a M< 

 impression O n the minds of those with whom he con- 

 versed. Mis memory was extraordinarily retentive; and. 

 amidst the variety of his reading, he could recollect and 

 quote the most important i 'c\cry lx>k which 



he had at any time perused." See Dr Kelly's I.i/'c nf 

 John Dnllond, and the articles ACHROMATIC TELESCOPE. 

 ASTRONOMY, CI.MHUT, OPTUS, and TELESCOPE. (*) 



DOLPHIN. See ICHTHYOLOGY. 



DOM K, or CI-POLA, a kind of vaulted roof or cover- 

 ing, employed in architecture, in the 1 .shape of 

 portion of a sphere, ellipsoid, &c. and frequently con- 

 structed of masonry. Domes differ in some respect- 

 from common arches, which are cylindric concavitie-. 

 resting on parallel walls, and having therefore a curva- 

 ture only in one direction ; whereas domes, as al.-o 

 groins, have a double curvature, and derive a degree of 

 stability from this circumstance, which is ] >ecu I iarly de- 

 serving the attention of the architect. We shall treat 

 of this subject under the article GROINS, comprehend- 

 ing therein roofs formed upon curvilinear as well as up- 

 on polygonal plans. See GROINS; andCARPENTRY, Part 

 II. p. 528. (A. N.) 



DOME A, is the name of a town, situated on a river 

 of the same name, which is the principal branch of the 

 Tunkin Kivcr. and discharges itself into the Gulf of Tun- 

 kin, about 20 leagues north-east of the former, in North 

 I. at. 'JO' 1 SO'. The town of Domea is about six or se- 

 ven leagues from the mouth of the river, is situated 

 on the right hand side close to the shore, ami is a hand- 

 some place, containing about 100 houses. The Dutch 

 \e. -els that trade here generally lie before the town, 

 while the English vessel.- proceed about three miles far- 

 ther up, and erect bank-halls during the time that they 

 remain. As pilots are necessary to conduct vessels over 

 the bar at the mouth of the river, a number of them 

 live at a village called Batsha, situated near its mouth. 

 The vessels should anchor, and wait for a pilot, when 

 a small island, called Pearl Island, on the east side of 

 the road, is about N.N.E. and three miles distant ; and 

 when a mountain island, called the Elephant, is about 

 \.\V. by W. The river is about a mile wide at its 

 mouth. Its depth, in the northerly monsoon, is 26 

 feet, and in the southerly not above 1 8. See Millmrn's 

 (Mental Commerce, vol. ii. p. 458. (if) 



DOMESDAY-BOOK, contains a survey of most of 

 the lands in England, made by the orders of William 

 the Conqueror. The etymology of the name is rather 

 uncertain ; some suppose it to be derived from the cir- 

 cumstance that the survey was deposited in a place 

 called Dornu* ilei ; but the more probable derivation is 

 from dom, or doom, judgment ; because by this survey 

 all disputes rcc|tecting landed property, and the tenure 

 by which it was held, were to be decided. The origi- 

 nal and proper name seems to have been Dam 

 There is also some difference of opinion concerning the 

 object which W>Uiam hud in. view, in causing this sur- 



i y 



