During a short residence at Compiegne, which he made while he was a professed teacher of languages, ho appears to have paid some attention to plane-astronomy ; and when he formed a friendship with Lalande, N. Deasy, in whose family Delambre was domiciled as tutor to his eons, was prevailed on by the astronomer to fit up a small observatory for his use. In this Delambre acquired some skill in the manipulation of his instruments, and also in the management of tho formulae which are used in the particular classes of data that the structure of instruments enables us to obtain. Ifs then determined to devote his life to astronomy and its history. The learning requisite for the history of astronomy ho had already obtained, though he had probably at this time read comparatively few of the book., and none of the manuscripts, which so arduous a task entailed upon him ; whilst of the incessant labour required by tho study of astronomy as a science he had possibly little idea, and of the skill which his future practice gave him his share was also very small. His ardour and perseverance however surmounted all the obstacles that opposed his progress; and never did Any man more completely illustrate the trite proverb, ' labor omuia vincit,' than Delambre.
When in 1781 the discovery of the planet Herschel was exciting the deep attention of astronomers, Delambro undertook the formation of tables of its motion, being probably urged to this by the Academy of Sciences having proposed the determination of its orbit as the prize of the year. That prize was awarded to Delambre. He then undertook the construction of his solar tables, as well as tables of the motions of Jupiter and Saturn. Shortly afterwards he commenced his tables of the eclipses of Jupiter, which occupied him some year,. When at a sitting of the Aaidemy Laplace communicated to that body the results of his researches ou the inequalities of Jupiter and Saturn, Delambro determined on constructing complete tables of the motions of those two plaucts, founded on those results, but more especially of those of Jupiter. The utility of such tables to the naviptor was a strong inducement to this undertaking, which ho entered upon with great ardent, and completed in an almost incredibly short period, when wo consider the great labour which they involved. His ecliptical tables ware presented to the Academy in 1792, as a competing paper for the prize on that subject which had been offered the preceding year; but he had been for several years engaged in their calculation. It is indeed very probable that the prize was offered to ioduco hire to complete them, as it was well known that he was engaged in the preparation of such tables. Such indeed is well known to be the general practice of that body ; and though it has occasionally done good, in bringing to a completion researches that might not so soon have been completed, it does this mischief—that it almost cuts off all competition, and inevitably gives the prize to a single candidate, by allowing him the advantage of a long previous preparation for it. Wo
cannot disapprove of the adjudication on this occasion, as Delambre's labours well merited the distinction; but we do not think the general practice calculated on the whole to do other than give delat to the members of the Institute themselves or their immediate friends.
When the project of fixing a standard of length was acceded to by the governments of France and England, Delambre and Mdchain were appointed to carry it into execution on the part of the former govern ment, by measuring the arc from Dunkirk to Barcelona. This laborious undertaking was carried on during the horrors of the French revolution, amidst almost every variety of difficulty and personal danger that can be conceived. 316chain dying during the progress of the work, the completion of it devolved wholly on Delambre. His perseverance, prudence, and zeal however eventually overcame all obstacles; and after eight years of unceasing labour and anxiety he obtained the measurements which constitute the data of the three volumes (1806-10) of his elaborate and invaluable work, 'Base du Systeme Mdtrique Ddcimal.' The Institute of France, which had watched over its progress, decreed him the prize for the most valuable work on physical science which bad appeared within the preceding ten years ; and it is difficult to conceive that a single objection could possibly arise to the propriety of that decision.
Of the continuation of Delambre's arc by Biot and Arago from Bar celona to Formentera, this is not the place to speak at length ; but it may be necessary to state that discrepancies which had long been observed in this latter arc were found by Puissant to arise out of actual errors committed by these observers.
Delambre was chosen an associate of almost every learned body in Europe, and was appointed by the French government a member of the Bureau des Longitudes, and Sderetaire Perpetuel de l'Inetitut de France, and one of the directors of the University of France. During the twenty years that he filled this latter important and responsible poet, his attention to its duties was unwavering, and his decisions remarkable for their justice and impartiality. His 6loges of the deceased ravens were indeed at the time considered somewhat strained as to praise ; but they were at least kindly meant to the friends of the deceased, and were gratifying to the vanity of the nation. They were remarkable for purity of style and for the researches into the history of the subjects to which the eulogised member had devoted himself.