ON THE HISTORY OF ASTRONOMY. " 601 



of the earth being one focus. And tlie primary planets moving in such 

 orbits round the sun, he had the satisfaction to see, that this inquiry, which 

 he had undertaken merely out of curiosity, could be applied to the greatest 

 purposes. Hereupon he composed near a dozen propositions relating to the 

 motion of the primary planets about the sun. Several years after this, some 

 discourse he had with Dr. Halley, who at Cambridge made him a visit, 

 engaged Sir Isaac Newton to resume again the consideration of this subject; 

 and gave occasion to his writing the treatise which he published under the 

 title of Mathematical principles of natural philosophy. This treatise, full of 

 such variety of profound inventions, was composed by him, from scarce any 

 other materials than the few propositions before mentioned, in the space of 

 one year and a half." 



The astronomers of Great Britain have not been less diligent in the practi- 

 cal, than successful in the theoretical part of the science. The foundation of 

 the observatory at Greenwich was laid in 1675, some years before the com- 

 pletion and publication of the discoveries of Newton. It is with the erection 

 of this edifice that the modern refinements in practical astronomy may be 

 said to have commenced; its immediate object was to assist in the perfection 

 of the science of navigation, and the series of observations, which have been 

 made in it/»has afforded an invaluable fund of materials to astronomers of 

 every country. A reward had been proposed, more than half a century 

 before, by Philip the Third, of Spain, for the discovery of a mode of determin- 

 ing the longitude of a ship at sea; and the states of Holland had followed 

 his example: a large reward was also offered by the French government in 

 the minority of Louis the Fifteenth. In 1674,. Mr. St. Pierre, a Frenchman, 

 had undertaken to determine the longitude of a place from observations of 

 the moon's altitude, and King Charles the Second had been induced to 

 appoint a commission to examine his proposq.ls. Mr. Flamsteed was con- 

 sulted by the commissioners, and was added to their number: he showed the 

 disadvantages of the method proposed by I\Ir. St. Pierre, and the inaccuracy 

 of the existing tables of the lunar motions, as well as of the catalogues of the 

 places of the stars, but expressed his opinion, that, if the tables were improved, 

 it would be possible to determine the longitudes of places with suiScient ac- 

 curacy by lunar observations. The king, being informed of Flamsteed 's repre« 



