214 ELEMENTS OF GENERAL SCIENCE 



In the United States large drainage systems have been 

 built that are in a way comparable to the irrigation systems. 

 One removes the water, the other adds it. In the Ever- 

 glades of Florida thousands of acres of fertile soil have been 

 made tillable by the construction of large drainage ditches. 



As people are coming to understand better the fundamental 

 importance of the soil in the life of all the nations, they are 

 making constant effort to render greater areas of arid and 

 swamp soils available for the use of men in agriculture, horti- 

 culture and gardening, and as homes for men. 



