OV RE-IRRIGATION AND ALKALI 



377 



reduction of the area of lower water-logged lands justify 

 the expenditure. The many materials used for this pur- 

 pose are discussed in special books on the subject. 



The oldest method of lining ditches is by masonry, the 

 first cost of which is not, by any means, the most expensive, 

 but requires relatively skilled labor, and later considerable 

 upkeep. Cement concrete, though it is most expensive, is 

 becoming the favorite material for lining ditches, for under 

 good supervision, it can be installed rapidly and with 

 ordinarily available labor. The great objection to cement 

 concrete linings is that in cold districts it is likely to break 

 unless carefully covered with earth or sand. Meanwhile 

 large, cement-lined canals, even in districts of very cold 

 winters, are giving excellent satisfaction. 



Crude mineral oil is also a favorite material for lining 

 irrigation ditches. It is heated and while still hot is sprink- 

 led with an ordinary road sprinkler over the bottom and 

 sides of the canal. It is then harrowed in, usually with a 

 chain puddler. This treatment reduces, largely, the 

 seepage. The older method of puddling thoroughly the 

 bottom and sides of the canal with clay is often the 



FIG. 107. Modified chain puddler. 



