480

HISTORY OF PHYSICAL ASTRONOMY.

1833. Mr. Baily has concluded, from a careful inspection of these ob-servations, that they do not possess sufficient value to render it desirablethat they should be printed*. Maskelyne had already intimated toDelamb re, that they were hardly preferable to those of Flamsteed f.Halley, indeed, was endowed with a mind of vast compass as well as extra-ordinary sagacity and power; but he seems to have undervalued thosehabits of minute attention which are indispensable to the attainment of ahigh degree of excellence in the practice of astronomical observation J.

The absence of any definite plan of operations in connexion with theRoyal Observatory of Paris has been already alluded to. The evilsarising from this cause did not fail soon to present themselves. Theastronomers engaged in prosecuting observations at that establishment,were frequently compelled to discontinue their labours, at the instance ofthe Government, for the purpose of executing scientific operations in theprovinces of France . This circumstance occasioned numerous interrup-tions in the records of the observations, which manifestly tended in agreat degree to depreciate their value. Moreover there was an incom-pleteness generally apparent in the observations actually made, arisingfrom the want of a presiding power to direct the labours of the establish-ment. These defects in the constitution of the observatory are describedin the following graphic terms, by Cassini I VChaeun venait observerdans les cabinets comme il Ventendait, quand et selon que cela lui plaisait,les astronomes novices pour s'exercer, les academiciens pour leur proprecompte. II n’y avait ni plan general suivi, ni chef pour diriger; de la, niaccord, ni ensemble, ni suite dans les travaux.”§

But although the Royal Observatory of Paris failed to attain such adegree of efficiency as was consistent with the flourishing condition ofscience in France , there was one important department of practicalastronomy in which that country took the lead of all other nations. Itwas in France that the length of an arc of the meridian was firstmeasured, upon principles so unexceptionable, and with so scrupu-lous a regard to accuracy in all the details of the operation, as to com-mand the confidence of astronomers generally in the result, and toinduce Newton to resume the ever memorable investigation which con-ducted him to his grand discovery of the principle of universal gravita-tion. It is to France also that astronomy owes the establishment of theellipticity of the earth, one of the most conclusive facts that can beadduced in favour of the Newtonian theory. This object was effected bya comparison of geodesical measurements, executed not merely on thesoil of France , but also in the arctic regions and under the equator.The operations connected with the establishment of these results ex-tended over nearly three-quarters of a century, and exercised the talentsof the most eminent astronomers of France who flourished during thatperiod. The name of Picard is imperishably associated with the origin of

* See a paper by Mr. Baity on this subject in vol. viii. of the Memoirs of the Astro-nomical Society .

f Histoire de l’Astronomie au Dixhuitieme Siecle, p. 134.t J It would appear, from the following expression, that Halley did not contemplate thepossibility of determining the apparent position of a celestial body within even 10" of thetruth:—“Utverum fatear, minuta secunda vel etiam dena secunda, instrumentis quan-tumvis affabre factis certo distinguere vix homini datum est.”— (Phil. Trans., 1716,p. 456.)

§ Memoires pour servir a 1’Histoire des Sciences , etc., p. 191.