LECTURE XXI. 



ASTRONOMY. 



THE EARTH. 



THE earth is nearly of a spherical figure. 

 The truth of this without having recourse to 

 scientific principles, will appear sufficiently evi- 

 dent from the voyages of celebrated navigators 

 such as Magellan, Sir Francis Drake, Lord An- 

 son, Cook, &c., who all set out, at different times, 

 to sail round the world, and by steering their 

 course continually westward, arrived at length at 

 the exact place whence they departed: which 

 could never have happened had the earth been 

 of any other form than spherical. 



This form is also apparent, from the circum- 

 stances which attend large objects when seen at 

 a distance on the surface of the sea. For when 

 a ship proceeds to sea, we first lose sight of the 

 hull or body of the vessel ; afterwards of the 

 rigging ; and at last discern only the top of the 

 mast ; which is evidently owing to the convexity 

 of the water between the eye and the object ; or 

 otherwise the largest and most conspicuous part 

 would have been visible the longest, as is mani- 

 fest from experience, in other cases. 



