HISTORY OF PHYSICAL ASTRONOMY.
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Hooke, without seeming to he aware of what Picard had done, has alsogiven an account of similar methods of adjustment in his “ Animadver-sions upon the Macliina Celestis of Hevelius .”*
The establishment of the national observatories of Paris and Green-wich immediately followed the remarkable improvements in practicalastronomy above alluded to. The Royal Observatory of Paris was com-menced in 1667, but was not finished before the year 1671. It was abuilding of great magnificence, designed by Claude Perrault , the famousarchitect of the Louvre; but it was constructed without due regard to thepurpose for which it was intended. It consisted of a quadrangular pileflanked by two massive towers. No means were provided in the con-struction of the building for enabling the astronomer to observe thecelestial bodies at all altitudes, by means of instruments sheltered underits roof, nor was it possible to repair the omission, on account of the enor-mous thickness of the walls. Dominique Cassini, who had arrived inFrance in the year 1669, in compliance with an invitation from Louis XIV. to reside in his capital, commenced his labours at the observatory on the14th of September, 1671. It is important to remark, however, that nospecial duties were assigned to him in connexion with that establishment,nor did he derive any emoluments from the French Government, in con-sideration of his services as an astronomical observer. A liberal pensionwas, indeed, granted to him upon his arrival in Paris , but this was on ac-count of the sacrifice he had made in leaving his native country to adornFrance by his talents j-. His superintendence of the Royal Observatorywas naturally suggested by the position which he occupied as first astro-nomer of France j, but his duties were altogether discretionary. Theother astronomers who had access to the Observatory , occasionally receivedallowances from the Government for their services, but there was no fixedsum set apart to provide for the annual maintenance of the establish-ment §. The consequence of this oversight was, that no definite plan ofobservation was projected, by an undeviating adherence to which the advan-tages of a national observatory can alone be realised. This circumstancelong continued to exercise an injurious influence on the progress of prac-tical astronomy in France .
The inherent vice in the construction of the Royal Observatory ofParis has been already alluded to. It might be expected that Cassini,who arrived in France when the building was in the course of erection,and in whose opinion upon any subject relating to astronomy theFrench Government reposed unbounded confidence, would have effectuallyused his influence in preventing so deplorable a sacrifice of the interestsof science to the fancy of the architect. It is true that he did not fail toremonstrate on account of the defective plan of the building, but themodifications proposed by him, shewed that his ideas were not in accord-ance with the existing requirements of practical astronomy. Among thealterations recommended by him, was the construction of an apartment in
* One of the most remarkable methods of adjustment practised by these astronomersconsisted in reversing the instrument so as to determine the error of collimation. It is acurious fact that the Arabian astronomer, Ibyn Jounis had already suggested a similarmethod of adjustment with respect to the gnomon. Thus, among several modes of veri-fying the perpendicularity of the instrument, he recommends to turn it round and makeobservations with it in two opposite directions. Delambre, Hist. Ast. Moyen Age , p. 102.
f Cassini IV., Memoires pour servir a I’Histoire des Sciences, p. 186, 4to, Paris , 1810.
X First astronomer, at least, in the estimation of the Court of Louis XIV .
§ “ Memoires pour servir a l’Histoire des Sciences, ” p. 186.