XVIII.] LAND AND WATER. 313 



parallel to the eastern side of the continent ; and thus 

 reproducing, on a smaller scale, the physical features of the 

 opposite shore. South America presents a similar section 

 (Fig. 94). A very sharp rise leads from the Pacific to the 

 range of the Andes, a, whence a broad plain stretches to 

 the Atlantic coast, relieved only by the highlands of 

 Brazil, b. 



It has been pointed out by Professor Dana ^ that, in all 

 parts of the world, the highest mountains border the largest 

 oceanic basins. This rule is strikingly illustrated by the 

 relief of the American continent. Thus, the Rocky- 

 mountains, which face the vast Pacific ocean, are con- 

 siderably higher than the Appalachians, or Alleghanies, 

 which are opposite to the much narrower Atlantic. 



America presents the grandest illustrations of fresh-water 

 phenomena to be found in any part of the world. Its river- 

 systems are framed on a gigantic scale ; the basin of the 

 Amazon, for instance, embracing an area of 1,500,000 

 square miles, (XV.) and that of the Mississippi about 

 980,000 (XL) miles. The drainage of the north-western 

 part of America is remarkable for its connection with a 

 chain of lakes which present a total area of 90,000 square 

 miles (I.) of fresh-water. These are knawn as lakes 

 Superior, Michigan, Huron, Erie and Ontario ; and their 

 waters are ultimately discharged into the Atlantic Ocean by 

 the River St. Lawrence. It is in passing from Lake Erie to 

 Lake Ontario, that the stream is suddenly precipitated to a 

 depth of 162 feet, to form the falls of Niagara. The 

 peculiar chasms through which some of the North American 

 rivers run, are illustrated by the Colorado canon figured on 

 P- 137- 



^ From whose Manual of Geology the contours of the sections in Figs. 

 92 to 94 are takea. 



