HISTORY OF PHYSICAL ASTRONOMY.

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time equidistant from the two observations, indicated the instant of thepassage of the body over the meridian. In applying this method to the sun,Picard did not fail to take into account the correction depending upon thechange of declination during the interval included between the two ob-servations. We have seen that this method of observation, which istermed the method of corresponding altitudes, had been already employedby the astronomers of India as well as by the Arabian astronomers, intracing the direction of a meridian line by means of observations of thesun. It does not appear, however, that they paid any attention to thecorrection above referred to. The application of the method, however, tothe celestial bodies generally, and the necessity of employing a correctionin the particular case of the sun, were distinctly pointed out by ThomasDigges in his “ Ala seu Scalm Mathematics," published at London in1573 *.

Picard’s labours at the Royal Observatory of Paris extend to 1682, inthe autumn of which year he died. The name of this astronomer is im-perishably associated with the improvements effected in practical astro-nomy in the seventeenth century. It cannot but be a matter of regret toevery person who takes an interest in the progress of astronomical science,that he w r as not selected to direct the national observatory of his country.Unfortunately his labours were not calculated to attract the attention ofthat class of persons whose attachment to astronomy is founded solely onthe pleasure to be derived from gazing at celestial phenomena. He ap-pears, moreover, to have been a man of a retiring disposition, who de-voted his talents to the cultivation of science for its own sake, regardlessalike of the applause of the multitude or the patronage of the great.Hence it happened that although he was, of all the astronomers of his age,perhaps the one most qualified to superintend the duties of an observatory,he was set aside by the government of his own country, and a foreignerappointed over the national observatory, whose labours, indeed, were of amore brilliant character, but were of infinitely less importance to the pro-gress of astronomical science than were those of Picard. It is deplorableto see the interests of a great country thus sacrificed to the caprices of acourt. The circumstance may well excite the indignation not merely ofFrenchmen , but of every person who is moved by the spectacle of truemerit thus contemptuously overlooked, while the individual who exhibitsqualities of a more meretricious nature is caressed and favoured.

La Hire commenced his observations at the Royal Observatory ofParis, in the year 1677. A mural quadrant of 5 feet radius, which Picardhad long solicited in vain, was finally adjusted, and permanently fixed inthe plane of the meridian on the 26th of April, 1683. La Hire con-tinued to make meridional observations with this instrument for a periodof more than thirty years; but unfortunately none of those later than theyear 1686 have ever been published.

The establishment of the Royal Observatory of Greenwich was only a fewyears posterior to that of the similar institution of Paris . The followingaccount of its origin is given by Flamsteed:—In 1675, a Frenchman , whostyled himself Le Sieur de St. Pierre, represented to the English govern-ment that he was in possession of a method of finding the longitude from

* The words of Digges are:—“ .... Non solum per solem orientem aut occi-dentern, seu sub sequalibus altitudinibus deprehensum (Prosthaphseroesi elapso inter ob-servationes tempore convenienti pro sobs motu non neglecta), sed etiam per Stellas fixasomnes.” (Supplementa, Capitulum Septimum, Canon Quartus.')