500 .

HISTORY OF PHYSICAL ASTRONOMY.

Astronomer Royal is no sinecure. One forms, however, a very imperfectidea of the heavy responsibility attached to the directorship of a nationalobservatory, from a mere inspection of the current labours of the establish-ment. The rapid progress of astronomy in modern times, is constantlysuggesting the necessity of modifying in some degree the instrumentsand methods of observation in actual use, and it is therefore desirablethat the individual appointed to such an office should possess a naturalaptitude for encountering every fresh difficulty that may occur in thepractice of observation, while at the same time he should maintain avigilant eye over the labours of his contemporaries, so as to availhimself of every really useful improvement that their researches mayelicit. It is hardly necessary to remark that sound judgment andstrong natural sagacity, combined with a profound knowledge of thevarious branches of physical science bearing upon practical astronomy, aswell as indefatigable energy, are indispensable to the due discharge ofsuch duties. It is universally admitted that the present AstronomerRoyal has proved himself to be eminently qualified for his arduous office,and that he has upheld in the most satisfactory manner the ancient repu-tation of the Observatory of Greenwich. Moreover, while lie has beenactively engaged in the promotion of objects more immediately relating topractical astronomy, he has not failed to contribute to the. advancementof astronomical science in general, by researches of a purely theoreticalcharacter. It ought to be remarked, also, that in virtue of his office lie isfrequently called upon by the Government to take an active part in scien-tific operations, which have only a remote connexion with astronomy, butwhich necessarily demand much careful attention. In all these labours,as well as in the multifarious details connected with the ordinary dischargeof his duties, Mr. Airy has uniformly displayed the same consummateability, the same untiring energy, and the same devotedness to the trustcommitted to his charge.

A retrospective view of the history of the Roj-al Observatory of Green-wich is calculated to excite feelings of agreeable satisfaction with respectto the mode in which that noble institution has fulfilled the end for whichit was originally designed. From the circumstance of the observationsextending with uninterrupted regularity over a long period of time, andfrom their undisputed excellence, they have formed almost the exclusivematerials by means of which astronomers in modern times have succeeded inbringing the tables of the sun, moon, and planets to their present high stateof perfection. The lunar theory, which so intimately concerns the interestsof navigation, has been especially indebted for its successive improve-ments to the observations made at Greenwich. It is also mainly by adiscussion of Greenwich observations that the constants of precession,and the other uranographical corrections, have been established with suchprecision in the present day. Delambre has justly remarked, that if bysome great revolution the sciences had perished, while this collection ofobservations alone, with some methods of calculation, had survived thegeneral wreck, there would still remain sufficient materials for recon-structing the whole edifice of astronomical science *. In the present day,when the attention of astronomers is being directed to questions of greaterdelicacy than any which had hitherto formed the subject of research, thematerials annually accumulated at Greenwich have acquired new claims

* Ilistoire tie l’Astronomic au Dixhuiticme Sieele, p. 627.