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IIALLEY HAMBURG. 



Daughter, on tle Truth of the Christian religion, 

 were translated into English ; and lie also wrote Let- 

 ters on Free-Thinking, designed to confute the rea. 

 tonings of French sceptical philosophers, who had 

 borrowed arguments in favour of their speculations 

 from his physiological theories. 



HALLEY, EDMUND, a distinguished mathemati- 

 cian and astronomer, was born in London, in 1656, 

 ;iinl was sent first to St Paul's school, and then to 

 (Queen's college, Oxford, of which he became a com- 

 moner in his seventeenth year. Before he was nine- 

 teen, he published A direct and geometrical Method 

 of finding the Aphelia and Eccentricity of Planets, 

 whic-h supplied a defect in the Keplerian theory of 

 planetary motion. By some observations on a spot 

 which appeared on the sun's disk in July and August, 

 1676, he established the certainty of the motion of 

 the sun round its own axis. August 21st, the same 

 year, he fixed the longitude of the cape of Good 

 Hope, by his observation of the occupation of Mars 

 by the moon. Immediately after, he went to St Hel- 

 ena, where he staid till 1678, making observations on 

 the fixed stars of the southern hemisphere, which he 

 formed into constellations. In 1679, he published 

 Catalogus Stellarum Australium, sive Supplementum 

 Catalog! Tychonici, &c., which procured him the ap- 

 pellation of the southern Tycho. He then went to 

 Dantzic to settle a dispute between the English phi- 

 losopher Hooke, and the famous Hevelius, relative 

 to the use of optical instruments in astronomical re- 

 searches, deciding in favour of the latter. In 1680, 

 he set off on a continental tour, and at Paris made 

 acquaintance with Cassini. After visiting Italy, in 

 1681 he returned to England, and settled at Isling- 

 ton, where he fitted up an observatory for his astro- 

 nomical researches. In 1683, he published his Theory 

 of the Variation of the magnetical Compass, in which 

 he endeavours to account for that phenomenon, by 

 the supposition of the whole globe of the earth being 

 one great magnet, having four circulating magneti- 

 cal poles, or points of attraction. His theory, though 

 unsatisfactory, is ingenious. The doctrines of Kep- 

 ler relative to the motions of the planets next en- 

 gaged his attention ; and finding himself disappoint- 

 ed in his endeavours to obtain information on the 

 subject from Hooke and sir Christopher Wren, he 

 went to Cambridge, where Newton, then mathema- 

 tical professor, satisfied all his inquiries. In 1691, 

 he was a candidate for the Savilian professorship of 

 astronomy at Oxford, which was obtained by doctor 

 David Gregory. According to Whiston, he lost this 

 office in consequence of his character as an infidel 

 in religion. For the purpose of making further ob- 

 servations relative to the variation of the compass, 

 lie set sail on a voyage in 1699, and, having travers- 

 ed both hemispheres, arrived in England in Septem- 

 ber, 1700. The spot at St Helena, where he erect- 

 ed a tent for making astronomical observations, is 

 distinguished by the appellation of Halley's Mount. 

 As the result of his researches, he published a gene- 

 ral chart, showing at one view the variation of the 

 compass in all those seas where the English naviga- 

 tors were acquainted. He was next employed to 

 observe the course of the tides in the English chan- 

 nel, with the longitudes and latitudes of the principal 

 headlands ; in consequence of which, he published a 

 large map of the channel. In 1703, he was engaged 

 by the emperor of Germany to survey the coast of 

 Dalmatia ; and, returning to England hi November 

 f that year, he was elected Savilian professor of 

 geometry on the death of doctor Wallis ; and he was 

 also honoured with the diploma of LL.D. He sub- 

 sequently published a Latin translation from the 

 Arabic of a treatise of Apollonius Pergaeus,a Greek 

 geometer, to which he made additions, to supply the 



place of what was lost. He next assisted his colleague, 

 doctor Gregory, in preparing for the press Apollonius 

 On Conic Sections. In 1719, he received the ap- 

 pointment of astronomer royal at Greenwich, where 

 he afterwards chiefly resided, devoting his time to 

 completing the theory of the motion of the moon, 

 which, notwithstanding his age, he pursued with en- 

 thusiastic ardour. In 1721, he began his observa- 

 tions, and, for the space of eighteen years, he scarcely 

 ever missed taking a meridian view of the moon 

 when the weather was not unfavourable. In 1729, 

 lie was chosen a foreign member of the academy ot 

 sciences at Paris. He died January 14, 1742, at 

 Greenwich ; and he was interred at the church of 

 Lee, in Kent. In 1752 appeared his Astronomical 

 Tables, with Precepts, in English and Latin, for com- 

 puting the places of the Sun, Moon, Planets and 

 Comets (4to); and he was the author of a vast mul- 

 titude of papers in the philosophical Transactions. 



HALO is an extensive luminous ring, including a 

 circular area, in the centre of which the sun or moon 

 appears ; whose light, passing through an interven- 

 ing cloud, gives rise to the phenomenon. Those 

 about the moon are most common. When the sun 

 or moon is seen through a thin cloud, a portion of 

 the cloud round the sun or moon appears lighter than 

 the rest, and this luminous disc is called a corona. 

 Coronas are of various sizes, but they seldon exceed 

 10 in diameter ; they are generally faintly coloured 

 at their edges. Frequently, when a halo encircles 

 the moon, a corona surrounds it. Parhelia, or 

 mock suns, vary considerably in general appearance : 

 sometimes the sun is encircled by a large halo, in the 

 circumference of which the mock suns usually appear, 

 which have often small halos round them. 



HAMADRYADS, in mythology ; eight daughters 

 of Hamadryas, by her brother. They received their 

 names from trees, and are the same as the Dryads, 

 (q. v.) They were conceived to inhabit each a parti- 

 cular tree, with which they were born, and with 

 which they perished. Whoever spared a tree to their 

 entreaties, they rewarded, while the destroyer of 

 groves was sometimes severely punished. See 

 Erisichthon. 



HAMAH ; a place in Syria, famous as Abulfeda's 

 birthplace. It has, according to Burckhardt, from 

 60 to 100,000 inhabitants, who live chiefly by manu- 

 facturing silk and cotton. 



HAMAN ; a name meaning full of grace. See 

 Esther. 



H AMANN, JOHN GEORGE, who called himself the 

 Northern Magian, was born at Konigsberg, in 1730, 

 travelled about in different parts of his native coun- 

 try, was private tutor in several places, received an 

 office in the customs at Konigsberg, in 1777, and 

 died at Munster, in 1788. Between 1759 and 1784, 

 he published several humorous works, whose value 

 the public did not then appreciate ; but since Herder, 

 Jacobi, Goethe and Jean Paul Richter have spoken of 

 them with approbation, they have been republished 

 (Leipsic, 18211825.) 



HAMBURG, the most considerable of the free 

 cities of Germany, is situated about eighty miles from 

 the mouth of the Elbe, upon the northern bank of the 

 river, which is navigable for large vessels as far as 

 this port. The circuit of the city is about 22,000 

 feet. In the northern part is a lake, formed by the 

 small river Alster, which runs through the city into 

 the Elbe, and turns several mills. An arm of the 

 Elbe enters the city from the east, and is there divid- 

 ed into a number of canals, which take various direc- 

 tions, till they unite, and join the Alster in the sou- 

 thern part of the city, where they form a deep har- 

 bour for ships, which communicates with the main 

 branch of the river. Here is a large space enclosed 



