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HISTORY OF PHYSICAL ASTRONOMY.
gested the principle of repetition as a means of obviating the errors ofdivision in astronomical instruments. The idea of that astronomer wasnot, however, realised till the year 1787, when it was at length appliedsuccessfully by Borda, a French officer of Marine, distinguished by philo-sophical acumen and strong practical talents.
In the construction of tables of the various planetary bodies, an objectof research which may be said to form the connecting link between theo-retical and practical astronomy, the labours of Delambre would suffice toassign to him a high place in the history of astronomy, even although hepossessed no other claims to the recollection of posterity. The method ofequations of condition, the utility of which Mayer originally exhibited inhis admirable researches on the libration of the moon, was employed withgreat success by Delambre , in the year 1785, in correcting the elementsof the solar orbit by means of Maskelyne’s observations. His tables ofthe planets Jupiter, Saturn, and Uranus, and of the satellites of Jupiter ,which shortly afterwards appeared, as well as his solar tables, which werepublished at a later period, were all admirable attestations of his perse-verance and skill. He may be said to have been the first who submittedmasses of observations to a systematic process of treatment, deducing inthis manner, from their totality, an accuracy of result which was unattain-able by a succession of partial operations*.
About the commencement of the present century, an improvement waseffected in the organization of the Royal Observatory of Paris. At thesame time, two excellent mural quadrants, one of which was constructedby the celebrated Bird, were erected in suitable apartments. Hence-forward the observations assumed a character of regularity and trust-w’ortliiness hitherto unknown, and were destined, in consequence, to provereally serviceable in conducing towards the advancement of theoreticalastronomy. In recent times, when the duties of its directorship have beenconfided to M. Arago, the Royal Observatory of Paris has attained a highdegree of efficiency. Observations are now constantly made at that esta-blishment, both by direct and reflected vision, with two mural circles con-structed by French artists of acknowledged eminencef. The brilliantresult which M. Le Verrier deduced from his researches on the perturba-tions of Uranus , based to a considerable extent upon data procured fromthe registers of the Royal Observatory of Paris, was a graceful homage tothe illustrious philosopher, at whose suggestion he was induced to under-take an examination of the subject.
In no country has practical astronomy made more rapid progress duringthe present century than in Germany . The labours of Bessel and a hostof eminent astronomers, afford ample confirmation of the truth of thisremark. It must be allowed, also, that in the construction of astronomicalinstruments, the German artists have attained a degree of excellencewhich is unsurpassed in any other country of the world.
Denmark still continues to sustain her ancient reputation by her patron-age of astronomical science. In M. Schumacher, whose recent death has
* Jean Baptiste Joseph Delambre was born at Amiens , in the year 1749. He died atParis in 1822.
+ One of the mural circles was executed by Gambey, an artist who appears to haveattained a very high degree of excellence in the art' of graduation. According toM. Faye, the probable error of the interval between two consecutive points of divisionof the circle constructed by him for the Royal Observatory of Paris, is less than 0" - l08.( Comptes Rendus, tome xxvii., p. 640). Gambey died in 1847.