ASTRONOMY. 3 



the Comets , and are also to be considered hereaf- 

 ter. 



4. The Earth is a body bounded by a surface, 

 nearly spherical, the diameter of which is ex- 

 ceedingly small, compared with the distance of 

 the fixed stars. 



a. The round or globular figure of the earth is infer- 

 red from many phenomena. 



1 . From the appearance of ships at different dis- 

 tances from one another, and of the land when 

 approached from the sea. 



2. From the circum-navigation of the globe. 



3. From the conical shadow of the earth, as seen 

 in eclipses of the moon. 



b. The circumference of the earth is nearly 25020 

 miles ; its diameter 7910 miles, and a degree some- 

 thing more than 69. 



These measures are not given as correct. The 

 method of ascertaining them with precision 

 will be afterwards explained. 



c. The smallness of the diameter of the earth compa- 

 red with the distance of the fixed stars, is inferred 

 from this, that the circles which those stars appear 

 to describe, are the same to spectators in all parts 

 of the earth, and also that the angles subtended by 

 the distance of any two stars from one another, is 

 the same at all points on the earth's surface. 



Since 



