134 DISSERTATION SECOND. [ PART ,. 



of the earth ; and, therefore, the diurnal and annual revo- 

 lutions which were natural to the earth, were also natural 

 to the stone ; the stone would, therefore, retain the same 

 motion with the tower, and strike the ground precisely at 

 the bottom of it. 



It must be confessed, that neither of these logicians had 

 yet thoroughly awakened from the dreams of the Aristote- 

 lian metaphysicks, but men were now in possession of the 

 truth, which was finally to break the spell, and set the 

 mind free from the fetters of prejudice and authority. An- 

 other charge, against which it is more difficult to defend 

 Tycho, is his belief in the predictions of astrology. He 

 even wrote a treatise in defence of this imaginary art, and 

 regulated his conduct continually by its precepts. Credu- 

 lity, so unworthy of a man deeply versed in real science, 

 is certainly to be set down less to his own account than 

 to that of the age in which he lived. 



3. Kepler and Galileo. 



Kepler followed Tycho, and in his hands astronomy 

 underwent a change only second to that which it had un- 

 dergone in the bands of Copernicus. He was born in 

 1571. He early applied himself to study and observe the 

 heavens, and was soon distinguished as an inventor. He 

 began with taking a more accurate view of astronomical 

 refraction than had yet been done, and he appears to have 

 been the first who conceived that there must be a certain 

 fixed law which determined the quantity of it, correspond- 

 ing to every altitude, from the horizon to the zenith. The 

 application of the principles of opticks to astronomy, and 

 the accurate distinction between the optical and real in- 

 equalities of the planets, are the work of the same astrono- 



