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OBSERVATORIES, ASTRONOMICAL. 



OCCULTATION. 



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was commenced in 1637, but it was not completed until the year 1656. 

 The first astronomer who was appointed to the direction of its labours 

 was Longomontanus, the celebrated pupil of Tycho Brahe. 



In the latter part of the 17th century a great impulse was given to 

 practical astronomy by the invention of the micrometer, and the appli- 

 cation of telescopic sights to the observation of the heavenly bodies. 

 During this period the observatories of Greenwich and Paris were 

 erected. We proceed to give a brief sketch of the history of the 

 former of these institutions, although as regards priority of establish- 

 ment the Paris Observatory has the advantage by a few years. 



The Royal Observatory of Greenwich was established in the year 

 1675. The foundation stone of the building was laid on the 10th of 

 August, and it was finished in less than twelvemonths afterwards. 

 Flamsteed was appointed Astronomer Royal, with a salary of 10(M. a- year. 

 In the warrant of Charles II. for the payment of his salary, he is styled 

 " our Astronomical Observator ; " and he is directed " forthwith to apply 

 himself with the most exact care and diligence to the rectifying the 

 tables of the motions of the heavens, and the places of the fixed stars, 

 BO as to find out the so much desired longitude of places for the per- 

 fecting the art of navigation." Flamsteed took up his residence at the 

 Observatory on the 10th of July, 1676, and shortly afterwards com- 

 menced his duties as an observer. lu this capacity he continued to 

 officiate till his death, which occurred towards the close of the year 

 1719. His observations are collected in an important work, entitled 

 ' Historia Ccclestis Britannica,' published in three volumes folio ; the 

 third volume contains a catalogue of 2935 stars, reduced to the begin- 

 ning of the year 1689. 



The second director of the Greenwich Observatory was the cele- 

 brated Edmund Halley. His earliest observation is dated October 1, 

 1721. His labours were chiefly confined to observations of the 

 moon. The results of these observations are inserted at the end of 

 his planetary tables, published in 1749. No other observations made 

 by this astronomer during his directorship of the Greenwich Observa- 

 tory have been published. The original records of his labours are 

 deposited in the Royal Observatory in four small quarto volumes. 

 Upon the recommendation of Francis Baily, a copy of these observa- 

 tions was taken by order of the Lords Commissioners of the Admiralty, 

 and presented to the Royal Astronomical Society in the year 1832. 

 Halley died on the Hth of January, 1742. 



Halley was succeeded in the office of Astronomer Royal by Bradley, 

 who had already rendered his name for ever illustrious by his dis- 

 covery of the aberration of light. In 1749, the Observatory having 

 been furnished with a brass quadrant of eight feet radius, constructed 

 by the celebrated artist, Bird, Bradley commenced a series of observa- 

 tions with the new instrument, which be continued to prosecute till 

 shortly before his death in the year 1762. The results of his labours 

 were subsequently published at the expense of the University of 

 Oxford in two folio volumes, the first volume in 1798, under the 

 u]*jrintendeuce of Dr. Homsby, and the second in 1805, under the 

 editorship of Dr. Robertson. 



Bradley's observations of the stars have been reduced and discussed 

 by the celebrated Bessel in a work published at Konigsberg, in one 

 volume folio, in the year 1818, entitled,' Pundamenta Astronornuc pro 

 anno 1755,deductaexobservationibu8viri incomparabilis James Bradley, 

 in specula Aatronomica Grenovicensi per annos 1750-62 institutis.' 



Bradley is universally regarded as one of the greatest observers of 

 ancient or modern times. The year 1750, when he commenced his 

 labours with Bird's quadrant, may be considered as the epoch whence 

 date observations comparable in precision with those of the present 

 day. Henceforward the observations made at Greenwich have been 

 employed almost exclusively in all the more important investiga- 

 tions of astronomy. Nor must we omit to state, that it was during 

 his career as Astronomer Royal that Bradley made the series of 

 observations, which resulted in his great discovery of the nutation of 

 the earth's axis. 



The successor of Bradley was Dr. Bliss, Savilian Professor of 

 Geometry in the University of Oxford, who (lied in 1765. The next 

 Astronomer Royal was the famous Dr. Maskelyne. His observations 

 embraced the determination of the positions of the sun, moon, and 

 planets, and a select number of stars ; and he continued to adhere to 

 this plan throughout the whole period of his career. Maskelyne first 

 introduced the practice of observing the transit of a star at five 

 vertical wires of the telescope. He wa* also the first who noted the 

 transit of a star in terms of tenths of a second. His death occurred in 

 the year 1811. The results of his observations have been published 

 in four folio volumes. 



Maskelyne was succeeded by Pond, who had already distinguished 

 himself as a practical astronomer, having in the year 1806 communi- 

 cated a paper to the Royal Society, in which he demonstrated that the 

 braaa quadrant of the Ruyal Observatory had undergone a change of 

 form since its erection in Bradley*s time. It was doubtless this 

 circumstance which induced Maskelyne to solicit from the Government 

 attraction of a in 1 1 I six i'evt diameter by Troiurl 



-t which was complied with ; but the instrument was not quite 

 finished at the time of his death. Soon after bis accession to the office 

 of Astronomer Royal, Pond commenced a series of observations with the 

 mural circle, in the prosecution of which he evinced a high degree of 

 H<- first introduced the practice of observing a star by direct 



ABI8 ASD SCI. DIV. VOL. VI. 



and reflected vision. The objects of his labours, besides the sun, moon, 

 and planets, included also a considerable number of the stars. The 

 observations in right ascension at the Royal Observatory, subsequently 

 to the year 1816, were made with a new transit instrument of ten feet 

 focal length, constructed by Troughton. In 1833, Pond published a 

 catalogue of 1112 stars, which proved of great value to the practical 

 astronomer. He retired from office in 1835, and died in the following 

 year. 



Pond was succeeded by Mr. Airy, who still continues to hold the 

 office of Astronomer Royal. He had been previously Plumiau Professor 

 of Astronomy in the University of Cambridge, and had also been 

 Director of the Cambridge Observatory since the year 1S28. While 

 engaged in the latter capacity he set the example of reducing all his 

 observations as soon as they were made, a practice which has since 

 been adopted at all public observatories. This eminent astronomer 

 has signalised the period of his career at the Royal Observatory by 

 numerous operations of great importance. Upon his recommendation, 

 the Lords Commissioners of the Admiralty defrayed the expenses of 

 reducing all the observations of the moon aud planets made at Green- 

 wich from 1750 to 1830. The results for the planets were published 

 in 1846, in one quarto volume ; those relating to the moon were given 

 to the public in 1848, in two large quarto volumes. Several important 

 catalogues of stars have emanated from the Royal Observatory during 

 Mr. Airy's directorship. [ASTRONOMY.] In the instruments of the 

 Observatory great improvements have also been effected. In 1847 an 

 altitude and azimuth circle of a peculiar construction (termed an 

 altazimuth) was erected, for the special purpose of making observa- 

 tions of the moon out of the meridian. In 1851 a powerful transit 

 circle was erected, and henceforward all observations, both of right 

 ascension and polar distance, were made with the same instrument. 

 In 1852, an instrument termed the reflex zenith tube was erected, 

 the object of which is to make observations near the zenith, mainly for 

 the purpose of determining the value of aberration. In 1853 the 

 American method of recording transits of stars by electro-magnetism 

 was introduced at Greenwich. In 1859, observations were commenced 

 with a magnificent equatorially mounted refractor of 1 2 inches aperture. 

 It may be remarked, finally, in connection with this brief sketch of the 

 Royal Observatory, that a great number of chronometers for the 

 Admiralty are being constantly rated at the same establishment. 



The other public observatories of the British Isles are those of 

 Oxford, Cambridge, Portsmouth, Durham, Liverpool, Edinburgh, 

 Glasgow, Dublin, and Armagh. Of private observatories may be men- 

 tioned the following : The observatory of Mr. Bishop, Regent's Park ; 

 the observatory of Mr. Warren De La Rue, Cranford, Middlesex ; the 

 observatory of Mr. Carrington, Redhill ; the observatory of Mr. Whit- 

 bread, at Cardiugton, in Bedfordshire ; the observatory of Dr. Lee, at 

 Hartwell ; the observatory of Lord Wrottesley, at Wrottesley Hall ; 

 the observatory of Mr. Lasaell, at Bradstoues, near Liverpool ; and the 

 observatory of the Earl of Uosse, at Birr Castle, Ireland. 



The Royal Observatory of Paris was commenced in the year 1667, 

 but was not completed until 1671. Its early history was illustrated 

 by the labours of Dominique Cassini and Picard. M. Le Verrier, one 

 of the independent discoverers of the planet Neptune, is the present 

 director of that establishment. The only other \ ublic observatories 

 of France are those of Marseille and Toulouse. 



Perhaps no country in Europe is so richly endowed with public 

 observatories as Germany. In the north of Germany we find the 

 observatories of Berlin, Konigsberg, Breslau, Bonn, Gottingen, Gotha, 

 and Hamburg ; in the south there are the observatories of Vienna 

 and Munich. The observatory of Kb'nigsberg is celebrated for having 

 been the scene of the labours of the illustrious Bessel. 



In Italy there are numerous public observatories, of which the most 

 famous is the observatory of the Collegio Romano, Rome, directed by 

 the distinguished astronomer, Professor Secchi. 



In Russia great efforts have been made during the present century 

 to promote the cultivation of astronomy. The Imperial Observatory 

 of Pulkowa, directed by the celebrated astronomer M. Struve, is perhaps 

 the most magnificent institution that has ever been established for the 

 advancement of practical astronony. There is also in Hussia the 

 observatory of Dorpat, directed by Professor Mueller ; and the obser- 

 vatory of Moscow, of which Professor Schweizer is director. 



Observatories have been established throughout the other countries of 

 Europe. A list of these establishments is given in the article ASTRONOMY 



In the United States of America great progress has been made 

 during the last quarter of a century, in the cultivation of practical 

 astronomy, and a number of flourishing observatories are now in 

 active operation. Of these the most celebrated are the National 

 Observatory, Washington, and the Observatory of Harvard College, 

 Cambridge, Massachusetts. 



OBTUSE, opposed to acute, is applied to an angle which is greater 

 than one right angle and less than two. 



OCCULTATION. This word, which might serve to design any 

 eclipse of one heavenly body by another, and even the effect of cloud 

 or fog, in particularly applied to the ecli^e of a fixed star by the nioon. 

 It has been seen [Moon] that the spiral course of the moon's real orbit 

 must bring her at some time or other in the course of a revolution of 

 the nodes (18$ years) at or near to every star situated within about 5 

 of the ecliptic either way. There are consequently continu.il occul- 







