2G 



THAT S IT ; 



perforation, so that water filters 

 through them. The dropping 

 ivell, 18, at Knaresborough, is 



167. 



an instance of this description. 

 A spring rises near a bed of 

 limestone rock, and the water 

 spreading itself over the upper 

 surface of a crag, which projects 

 ,over the road beneath ; the water 

 drops through in a shower of 

 large globules, and falling from 

 19 



ance. Diffusing itself over flat 

 countries, where there is insuffi- 

 cient drainage by natural or arti- 

 ficial means, water produces 

 fens, bogs, morasses, and marshes, 

 19. These form the abodes oi 

 aquatic birds and animals. In 

 tropical countries the water which 

 thus lodges amid rank vegetation 

 assumes a remarkable darkness 

 of colour, and produces black 

 swamps, 20. The darkness of 

 the water arises from strong 



168. 



a height of about thirty feet, 



169. 



vegetable solutions imparted by 

 the rank plants and herbs, which 



presents a very curious appear- j grow in the swampy grounds. 



