HISTORY OF PHYSICAL ASTRONOMY.

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ing a celestial object at one transit both by direct and reflected vision,founded upon a combination of simultaneous observations made with twomural circles*. A mural circle by Jones, that had been destined for theCape of Good Hope , was employed, along with Troughton’s circle, in test-ing the practicability of this method. The experiment having been at-tended with complete success, Pond solicited from the Government thepermanent use of the second circle, and his request being complied with,he now introduced the method into general practice.

Pond commenced his regular observations by direct and reflected visionin the month of September, 1825. This method of determining thezenith point continues still to be practised at Greenwich, except in so faras relates to the use of two circles, the present Astronomer Eoyal havingdevised a mode of effecting the same object by means of only one circle.

Pond did not fail to make regular observations of the sun, moon, and prin-cipal stars, but he devoted less attention to the planets than the importanceof improving their respective theories demanded. In sidereal astronomygenerally, his contribution to the existing stock of knowledge was muchmore extensive than that of his predecessor. His peculiar methods foreliminating the effects of instrumental error, were founded upon a skilfulcombination of masses of observations, and he was led in consequence todetermine the places of a considerable number of stars. In 1833 hepublished a catalogue of 1112 stars, which proved a valuable acquisition tothe practical astronomer. It is generally admitted to be one of the mostaccurate productions of the kind that has ever been given to the world.

In the autumn of 1835, Pond was compelled by ill health to resign hisappointment. The Government manifested a just appreciation of hismerits, by bestowing upon him a retiring pension, but he was not destinedlong to enjoy the fruits of their liberality. He died on the 7th of Sep-tember, 1836, and was buried at Lee in Kent, in the same tomb withHalley.

George Biddel Airy , Esq., the present Astronomer Royal, commencedhis labours at Greenwich as the successor of Pond, on the 2nd of October,1835. He had already earned a distinguished reputation by his re-searches on physical astronomy, and by his directorship of the Observatory of Cambridge, to which he was appointed in the year 1828. Duringthe period of his connexion with the latter establishment, he intro-duced a practice which did not fail to exercise an important influence onthe future character of the labour performed at public observatories inthis country. It had been hitherto usual for the directors of such estab-lishments, to confine their attention exclusively to observations of thecelestial bodies, leaving to others the task of their reduction. Flam-steed, indeed, deserves to be cited as an honourable exception to this re-mark; and with respect to his successors, the circumstance of theirhaving omitted to reduce their observations, must be attributed to thescantiness of the resources which the Government placed at their disposal,rather than to any inattention or apathy on their own part. There canbe no doubt, however, that the restriction of their labours to mere obser-vation, tended seriously to frustrate the very object for which public ob-servatories have been established, namely, the attainment of a moreaccurate knowledge of the movements of the celestial bodies; for few in-dividuals could muster sufficient courage to undertake the investigation of

* For a description of this method by Pond, see Hem. Ast, Soc., vol. ii., p. 499, et seq.