302 HISTORY OF FORMAL ASTRONOMY. 



CHAPTER V. 



.SEQUEL TO THE EPOCH OF KEPLER. RECEPTION, VERIFICATION, AND 

 EXTENSION OF THE ELLIPTICAL THEORF. 



Sect. 1. Application of the Elliptical Theory to the Planets. 



fTIHE extension of Kepler's discoveries conceining the orbit of Mars to 

 -I- the other planets, obviously offered itself as a strong probability, 

 and was confirmed by trial. This was made in the first place upon 

 the orbit of Mercury ; which planet, in consequence of the largeness 

 of its eccentricity, exhibits more clearly than the others the circum- 

 stances of the elliptical motion. These and various other supplemen- 

 tary portions of the views to which Kepler's discoveries had led, ap- 

 peared in the latter part of his Epitome Astronomies Copernicance, 

 published in 1622. 



The real verification of the new doctrine concerning the orbits and 



o 



motions of the heavenly bodies was, of course, to be found in the con- 

 struction of tables of those motions, and in the continued comparison 

 of such tables with observation. Kepler's discoveries had been founded, 

 as we have seen, principally on Tycho's observations. Longomontanus 

 (so called as being a native of Langberg in Denmark), published in 

 1621, in his Astronomia Danica, tables founded upon the theories as 

 well as the observations of his countryman. Kepler' in 1627 pub- 

 lished his tables of the planets, which he called Rudolphine Tables, 

 the result and application of his own theory. In 1633, Lansberg, a 

 Belgian, published also Tabulae. Perpetu&, a work which was ushered 

 into the world with considerable pomp and pretension, and in which 

 the author cavils very keenly at Kepler and Brahe. We may judge of 

 the impression made upon the astronomical world in general by these 

 rival works, from the account which our countryman Jeremy Horrox 

 has given of their effect on him. He had been seduced by the mag- 

 nificent promises of Lansberg, and the praises of his admirers, which 

 are prefixed to the work, and was persuaded that the common opinion 

 which preferred Tycho and Kepler to him was a prejudice. In 1636, 

 however, he became acquainted with Crabtree, another young astrono- 



Rhcticus, Narratio, p. 98. 



