CHAPTER XIX. 



FIGURE OF THE EARTH. CONSTRUCTION OF MAPS. 



In considering the form, size, and other characters of the 

 Thames basin, we found no occasion to trouble ourselves 

 about the shape and size of the earth as a whole ; and, as 

 what is true, in this respect, of the area of the Thames basin, 

 is true of all areas of the earth's surface, it is obvious that 

 all the facts stated in the last chapter might have been 

 ascertained by the ordinary processes of land-surveying, 

 and that they do not necessarily presuppose a knowledge 

 of the configuration of the world. 



One's earliest and most natural impression is that the sur- 

 faces of the land and sea are everywhere flat, if local elevations 

 are left out of consideration ; and, for many ages, it was tne 

 accepted belief of mankind that the land was a huge flat 

 cake surrounded on all sides by an illimitable ocean. But 

 when, in, 1520, Magellan, sailing westward from Europe, 

 passed round the southern end of South America ; and, his 

 ships keeping their bows continually in the same direction, 

 eventually reached the coasts of Asia, and thence returned 

 to the place from whence they set out, it was demonstrated 

 that, at any rate along the track he followed, the surface of 

 the earth was round. 



