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HISTORICAL VIEW OF THE

to our knowledge of the heavenly bodies. And in allthese we can, with just pride, observe, that our countryhas borne its full share.

We have alluded to Halley’s labours. He addedto them the glory of being the first to predict the re-turn of a comet. Having noticed an agreement in theelements of several which had appeared at successiveperiods, he concluded them to be reappearances of thesame body, obeying the law of an elliptic orbit. Heforetold a return in 1758, which was completely verified.

Bradley, associated with Molyneux, commenced, in1725, that valuable series of observations which led tothe discovery of the aberration and the nutation of theearth’s axis. The former a consequence of the finitevelocity of light, the latter of gravitation.

The measures of the arc of the meridian were nowrepeated with increased accuracy in France , by La Hireand Cassini, but seemed to lead to the strange and pa-radoxical result of the earth’s figure being a prolate orlengthened , instead of a flattened or oblate, spheroid. This,however, was afterwards shown to be due to an error inthe fundamental measurement; and, in 1735, the com-parison of arcs, measured by Maupertuis and others inLapland, and La Condamine in Peru , established theoblate figure.

Arcs were also measured in Italy, by Boscovich , in1750; at the Cape, by La Caille, in 1752; and inAmerica , by Mason, in 1764.

The two transits of Venus , in 1761 and 1769 , wereboth, and especially the last, most sedulously observedby astronomers sent to various stations in different partsof the globe, at the expense of the principal govern-ments in Europe ; and the important results of the sun’sparallax completely settled.

The invention of Hadley’s quadrant in 1731 fur-nished the. instrumental means, created as it were forthe express purpose of observations on board ship : andthe improved lunar tables supplied the data for the easyand complete adoption of the method of lunar distances