XIV 



PAGE 



, The Chaldeans look upon comets as ; .anetary 



bodies ., . . 104 



S, 4. Aristotle and Stobeeus assert, that comets are 

 . wandering stars, which appear to us only in par- 

 ticular parts of their orbits . . ib. 



5. Seneca clearly discusses the subject . 105 



6. Reflection . . ib. 



CHAP. XVIII. 



Of the Refraction. of Light, and Astronomical 

 Refraction, and of Perspective. 



1, 2. The advantages "Of the eastern nations in 'the 



study of astronomy . 106107 



Their invention of the ribrations of the pendulum, 

 dials, c. . . . ib. 



3) 4. The discovery of the refraction of light as ancient 



as ihe time.of Ptolomy . 107108 



5. What is the cause of astronomic refraction . ib. 



6. Th.e difference of magnitude in stars accounted for 109 



7. Perspective clearly. understood and described by the 



'ancients, . . j MO 



8. Various conjectures as t the image of the sun, by 



collecting its rays .. . in 



CHAP! xix. 



' Of the Discoveries of the Ancients in Mathematics^ c. 

 l. Introduction . . lift' 



