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who is dill better known for his admiraUc invention of the 

 reflefliiig quadrant or fcftor, now called by his name, and 

 which is univcrfally iifcd at fea, and in all nice obfcrvations. 

 Mr. Bird alfo, about the middle of the eighteenth centurVi 

 rendered great fervices to aftrouomy, by his method of con- 

 ftriifling and dividii'g large aflroMomicalinlltumentS ; which 

 has fince been carried to the greatcil degree of perfeClion 

 by that admirable artill Mr. John Ramfden, whofe recent 

 death will be long regretted by aftronomers, and men of 

 fcience in general. RefleAing telefccpes were likewife not 

 lefs improved by Mr. Short, \vho alio firil executed the di- 

 vided objed-glafs micrometer, which had been propofcd and 

 defcribed by M. Louville and others. 



Thus the aftronomical improvements in the laft cen- 

 tury, have been chiefly owing to the greater perfeftion of 

 inttruments, and to the eftablilhment of regular obfervatories 

 in various parts of Europe. Romer, a celebrated Daniih 

 aftronomer, firil made \ife of a meridian teleicope ; and by 

 obferving the eclipfes of Jupiter's fatellites, was led to his 

 difcoveryof the motion of light, vvhich he communicated 

 to the academy of fciences at Paris, in 1 675. Mr. Flamlleed 

 was alfo appointed the firil aftronomer royal at Greenwich, 

 about the fame time, where he obferved all the celeftial phje- 

 nomena for more than forty-four years ; and as the fruits of 

 his labours, publifhed a catalogue of 3000 ftars, with their 

 places, to the year 1688, as alfo new folar tables, and a 

 theory of the moon according to Horrox. Caffini, alfo, 

 the firil French aftronomer royal, greatly didinguifhed him- 

 felf by his numerous obfcrvations on the Am, moon, and 

 planets, and by the improvements he made in the elements 

 of~their motions. 



In 1 7 19, Mr. Flamfteed was fucceeded by Dr. Halky, 

 the friend of Newton, and a man of the firft eminence in all 

 the claffes of literature and fcience ; who had been fent at 

 the early age of twenty-one, to the ifland of St. Helena, to 

 cbferve the fou them liars, a catalogue of which hepubliflicd 

 in 1679 ' ^"'^ ^ ^^^^ years afterwards he gave to the public, 

 his " Synopfis AllronomiiE Cometica^," in which he ven- 

 tured to predift the return of a comet in 1758, or 1759. 

 He was thefirft who difcovered the acceleration of the moon's 

 mean motion; and is the author of a very ingenious method 

 for finding her parallax, by three obferved places of a folar 

 eclipfe : he alfo fhewed the ufe that might be made of the 

 approaching tranfit of Venus, in 1 76 1, in determining the di- 

 ftance of the fun from the earth ; and recommended the 

 method of determining the longitude by the moon's ditlauce 

 from the fun and certain fixed ftars, which has fince been 

 carried into execution at the inftance of the prefent aftro- 

 nomer royal. Dr. Halley alfo compofed tables of the fun, 

 moon, and planets, with which he compared the obfcrva- 

 tions he made ot the moon at Greenwich, amounting to 

 near 1500, and noticed the differences. About this time, 

 an attempt was made in France, to meafure a degree of the 

 earth, which was the occafion of a warm difpute concerning 

 its figure. M. Caflini concluded, from the meafurenient of 

 Picart, that it was an oblong fpheroid ; but Newton, from 

 a confideration of the laws of gravity, and the diurnal mo- 

 tion of the earth, had determined its figure to be that of an 

 oblate fpheroid, flattened at the poles, and protuberant at the 

 equator. To determine this point, Louis XV. ordered two 

 degrees of the meridian to be meafured, one under or near 

 the equator ; and the other as near as pofTible to the pole, 

 the refult of which arduous undertaking was a confirmation 

 of Newton's inveftigation. MefT. Maupertuis, Clairault, &c. 

 were employed on the northern expedition ; and Condamine, 

 Bougucr, Don UUoa of Spain, &e. on the fouthern ; who 

 all fullillcd their commilUons with great credit to thtmftlves, 



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and advantage to the tienccs, making many obfcrvations 

 bcfides thofe immediately conneftcd with this fubjeft. Among 

 others, it was found, by tiiofe who went to tlie fouth, that 

 the attradlion of the great mountains ot Peru had a fenfible 

 efFe£i on the plumb li.ies of their large ir.ftruments, which 

 afforded an experimental proof of th.e Nevitonian d<,ftrine 

 of gravitation, that has fince been completely verified by 

 the obfcrvations of Dr. Mafkclyne, made on the mountain 

 Schehallien in Scotland. See Attraction of Mounlains. 



On the death of Dr. Halley, in 1742, he was fucceeded 

 by Dr. Bradley, who has rendered himfelf highly celebrated 

 by two of the finefl difcoveries that have ever been made 

 in aftronomy, the aberration of light and the nutation of 

 the earth's axis. Among other things, he alfo formed new 

 and accurate tables of the motions of Jupiter's fatellites, as 

 well as the moft corre6l table of refraclions yet extant. Alfo, 

 with a large tranfit inftrnment, and a new mural quadrant 

 of eight feet radius, conlhufted by Bird, in 1750, he made 

 an immenfe number of obfcrvations, for fettling the places 

 of all the ftars in the Britifh catalogue, together with near 

 150 places of the moon, the greater part ot which he com- 

 pared with Mayer's tables. 



Dr. Bradley was fucceeded in 1762, in his office of aftro- 

 nomer royal, by Mr. Blifs, hut who, being in a declining 

 ilate of health, died in 1765, and was fucceeded by Nevil 

 Mafivelyne, D. D. the prefent aftronomer royal, who has 

 rendered confiderable l\;rvice3 to this fcience, by his publica- 

 tion of the " Nautical Almanac" the " Requifite Tables," 

 &c. and more particularly by the great afTiduity and zeal he 

 has difplayed in bringing the lunar method of determining 

 the longitude at fea into general praflice. 



In the mean time, many other eminent mathematicians, 

 both of our own, and other countries, were afTiduoufly em- 

 ployed in endeavouring to promote the fcience of aftronomy. 

 The theory of the moon was particularly confidered by 

 Mefs. Clairault, d'Alembert, Euler, Simpfon, Walmfley, 

 and Mayer ; the latter of whom computed a fet of lunar 

 tables, tor which, on account of their fuperior accuracy, 

 he was rewarded with a premium of 3000I. by the board 

 ot longitude, who brought them into ufe in the computa- 

 tion of the nautical ephemeris which was publiflied by their 

 order. Some veiy accurate tables of the fatellites of Jupiter, 

 vpcre alfo compofed from obfcrvations by Mr. Wargentin, 

 an excellent Swedifh aftronomer, and which have fince been 

 correded by the author, fo as to render them fuperior to' 

 any yet publifhed. 



Among the French aftronomers who have alfo contri- 

 buted to the advancement of this fcience, we are particu- 

 larly indebted to M. de la Caille for an excellent fet of 

 folar tables, in which he has made allowances for the at- 

 traftions of Jupiter, Venus, and the Moon, as well as for 

 the obiervations which he made at the cape of Good Hope, 

 iu concert with the moft celebrated aftronomers in Europe, 

 in order to determine the parallax of the fun, moon, and 

 the planet Mars ; and for adjulling the places of the ftars 

 in the fouthern hemifphere, which he has done with great 

 accuracy. In Italy alfo the fcience was cultivated with 

 great fuccefs by S. Bianchini, Bofchovich, Frifi, Manfredi, 

 Zanotti, and others ; and in Germany, by Euler, Mayer, 

 Lambert, &c. 



Such was the ftate of aftronomy when Dr. Herfchel, by 

 augmenting the powers of telefcopes beyond the mod fan- 

 guine cxpee^.ations, opened a fcene altogether unlocked for. 

 By this indefatigable obferver we are made acquainted with ' 

 a new primary planet belonging to our fyftem, called the 

 Georgium Sidus, attended by fix fatellites, which he difco- 

 vered ou the 13th of March 1781, and vvhich being at twice 



the 



