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longitmle at fea by obfcrving the moon's Usance from the 

 fun and certain fixed flar';, which is now io iucccftfuHy 

 pracHfcd in the Biitifli navy. 



Next after thefe was Nicholaus Copernicus, the cele- 

 brated veftorer of the old Pythagorean fyftem of the world, 

 wliich had been now fet afide ever fince the time of Pto- 

 Kmy. He was born at Thorn, in Polifli Prgffia, in 1473, 

 and having gone through a regular courfe of ftudies at Cra- 

 cow, and atte»aards at Rome, he was made by the intertft 

 of his uncle, who was biihop ot Wormia, a caftoii of Fraw- 

 enbirg ; in which peaceful retreat, after 36 years of ob- 

 fcrvations a.id meditations, he ellablifhed his theory of the 

 motion of the earth, with fuch new and demonftrative ar- 

 guments in its favour, that it has gradually prevailed from 

 that time, and is now univerfally received by the learned 

 throughout Europe. 



This great man, however, had not the fatisfaftion of wit- 

 neffiiig the fuccefs of his undertaking, being threatened by 

 the perfecutior of religious bigots on the one fide, and with 

 an obiHnate and violent oppofhion from thofe who called 

 themfelves philofophers on the other: it was not without the 

 greatell folicitations that he could be prevailed upon to give 

 up his papers to his friends, with pcrmiffion to make them 

 public; but from continued importunities of this kind, he at 

 length complied, and his book, "De Revolutionibus Orbium 

 Cceleilium," after being fupprcfled for many years, was at 

 length publiihed, and a copy of it brought to him a few 

 hours before his death. His difciple Rheticus, who has 

 rendered. great fervices to the mathematical fciences by his 

 extenfive tables of fines, tangents, and fecants, to every ten 

 feconds, was the firll who adopted his ideas ; but they made 

 but little progrefs till towards the beginning of the 17th 

 century. 



In this interval, however, the fcience was not wholly neg- 

 lefted. Nonius in particular wrote fevcral valuable treatifes 

 on Allronomy and Navigation, and invented fome ufeful in- 

 ftruments, more accurate than thofe before known ; one of 

 thefe being the aftronomical quadrant, on which he divided 

 the degrees into minutes, by a num.ber of concentric circles. 

 Apian alfo, in 1540, wrote a book called the " Casfarian 

 Allronomy," in which he fhews how to obferve the places 

 of the liars and planets by the aftrolabe ; to refolve aftrono- 

 mical problems by means of certain inllruments, and to pre- 

 dift and calculate eclipfes; and at the end of his work are 

 added obfervations of five comets, one of which has been 

 fuppufed to be the fam.e. with that defcribed by Hcvclius ; 

 and whofe return was accordingly looked for in the year 

 1789, but it did not appear. Gemma Frifius, who lived 

 about this time, is likewife ckferving of notice, as being the 

 firft v.'ho recommended time-keepers for finding the longitude 

 at fea. 



The hiftory of the fcience, about this epoch, alfo offers 

 US a great number of excellent practical ailronomers ; one 

 of the moll illullrious of whom was William IV. landgrave 

 of Hefle-Cairrl, who built an obfervatory in thnt city, and 

 furnifhcd it with a number of the bell inllruments that 

 could be obtained at that time, with which he made his own 

 obfervations. He alfo attached to himfelf the celebrated 

 ailronomers Rothman, and Julius Burgius, and with their 

 help formed a catidogue of 400 liars with their latitudes and 

 longitudes, adapted to the begmnirg of the year 1593. It 

 •was alfo Irom his prcfling folicitations, that Tycho Bi-ahe, 

 one of the greatell obfervcrs that ever exifted, jirocured the 

 advantages that he enjoyed under Frederic II. king of Den- 

 mark. 



This excellent Danifh allronomer, who was born at 

 Knudltorpin the county of Schoiien, in 1546, began to mani- 



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fcft his tafte for this fcience at the early agf of 14. An 

 eflpfc or th-- fun which happened in 1560, firll atti^^cd his 

 attention; and the juftnefs of the calculation which announ- 

 ced this phenomenon, infpired him with a (Irong defire of 

 undtrftanding the principles upon which it was founded. 

 But meeting with fome oppofition from his tutor, and a part 

 of his family, to thefe purlTuits, which probably ferved only 

 to increafe his attachment to them, he made a journey into 

 Germany, where he form.cd connexions, and entered into a 

 correfpondence with fome of the mod eminent ailronomers 

 of that country; particularly with the landgrave of Heffe, who 

 reeen'ed him in the moft flattering manner, and recommend- 

 ed him to the notice of his fovereign. Becoming by this 

 means better known, on his return to Denmark, ^Frederic 

 II. gave him thedittle ifland of Huen, at the entrance of 

 the Baltic, where he built an obfervatory, under the name 

 of Uraniburg, and in which, during a courfe of twenty- 

 years, he made a prodigious number of obfenations. 



His tranquillity, however, in this happy ret^eat, was, at 

 length interrupted; for foon after the death of Frederick, 

 which happened in 1596, he was deprived, through the af. 

 perfions of fome envious and malevolent perfons, of his ^ 

 penfion and ellablifliment, and was not even allowed to 

 follow his purfuits at Copenhagen ; a minifler of that 

 time, of the name of Walchendorp, having forbid him 

 to continue his obfervations. Happily, however, he 

 found a powerful protedor in the emperor R-odolphus II., 

 who ordered him to be properly provided for at his own ex- 

 pence, andgavehima commodious houfe at Prague. After re- 

 fiding in this city till the year 160 1, he was taken ofl" by a 

 fudden death, in the midll of his labours, and at an age 

 while he was yet capable of rendering great fervices to aftro- 

 nomy. 



This great man, as is well known, was the inventor of a 

 kind of Semi-Ptolemaic fyftem of allronomy, that was after- 

 wards called by his name, and v>hich he vainly endeavoured 

 to eftabhfh inftead of the Copernican or true fyftem. But 

 though he was not happy in this rcfpeft, he has been of 

 great ufe to allronomy by his numerous obfei-vations and 

 difcoveries. Among other things he was well acquainted 

 with the nature of rcfraftions (fee Refraction ) ; and hence 

 he was able to determine the places of a great number of 

 the fixed liars, with an accuracy unknown to former times. 

 He alio proved, againft the opinion whicli then pre\-ailed, 

 that the comets are higher than the moon (fee Comet) ; 

 a:id from his obfervations on this and the rtll of the pla- 

 nets, the theories of their motions were afterwards correcl- 

 ed and improved, fo that for thefe fervices he will always 

 be celebrated and efteemed by ailronomers. 



Tycho Brahe, in the latter part of his life, had for his 

 difciple and affillant the celebrated Kepler, who was born 

 in 1 57 1, at Wiel in the duchy of Wirtembeig, and was one 

 of thofe rare chtiradters that appear in the world only at 

 particulartimes, to prepare the way for new and important dif- 

 coveries. Like his mailer Tycho, he appears to have at- 

 tached himfilf to the fcience at a very early age ; and if it 

 be the privilege of genius to change received ideas, and to 

 announce truths which had never before been difcovcred, he 

 may jullly be confidered as one of the greatell men that liad 

 yet appeared. Hipparchus, Ptolemy, Tycho Brahe, and even 

 Copernicus himfelf, w^ere indebted for a great part of their 

 knowledge to the Egyptians, Chaldn;ans, and Indiatis, who 

 were their mailers in this fcience ; but Kepler, by his own 

 talents and indullry, has made difcoveries of which no traces 

 are to be found in the annals of antiquity. 



The philolophcr, the moft ufeful to the fciences, is he 

 who to a profound imagination unites a ferupulous judgment, 



and 



