42 



GENERAL CONSIDERATIONS 



fields, and when large, necessitate heavy expense for 

 bridges. The annual cost for cleaning out and keeping 

 in order is very considerable. For all these reasons 



Draiutile and Tile Hoe. 



it is usually cheaper and more satisfactory in the 

 long run to go to the expense of laying underdrains. 

 Temporary underdrains are sometimes made by filling 

 in the bottoms of ditches with poles or loose rocks 

 and covering them, or by inverting a wooden gutter 



