RIVERS, ETC. 25 



poles, or the north and south points of the earth, 

 forms islands and mountains of solid ice, which 

 never melts, even in the midst of summer. 



All the countries of the world are supplied with 

 fresh water, by streams which run through them. 

 Larger streams are called rivers, and run into the 

 sea: smaller streams are called rivulets. Many 

 rivers are very broad and deep. When a river is 

 so deep that large ships can sail upon it, we call it 

 a navigable river. The hollow in which the water 

 of a river flows is called its channel, or bed. The 

 margin of the bed is called the bank. In many 

 rivers there are places where the water tumbles 

 over steep precipices to a great depth. Such 

 places are called waterfalls, or cataracts. Pieces 

 of water, surrounded by land, are termed lakes. 

 There are lakes more than one hundred miles in 

 length and breadth. 



Questions. 



"What does the bottom of the sea consist of ] 



What is the appearance of the sea at night ? 



By what is this produced 1 



"Why is sea-water less liable to freeze than other water? 



What appearance has the sea at the two poles of the earth ? 



How are the countries of the world supplied with fresh 

 water ? 



What names are given to the streams of fresh water ? 



What is a navigable river 1 



What are waterfalls, or cataracts ? 



What name is given to large pieces of water surrounded by 

 land* 



C 



