INLAND DRAIXAGE 117 



MACHINE DITCHING 



The various types of ditching and trenching machines may be 

 divided into four general classes, as follows: (1) plows and scoops; 

 (2) wheel excavators; (3) endless-chain excavators; and (4) 

 scraper excavators. 



For construction of open, V-shaped ditches — the usual type of 

 anti-mosquito ditch — only the first two classes are generally 

 used. The endless-chain excavators, designed chiefly for 

 digging trenches for installation of pipe, which are filled up after 

 the pipe is laid, usually cut a narrow and, where necessary, a 

 deep ditch, with vertical banks. Owing to the possibility of 

 frequent cavings, a trench of such a shape does not, as a rule, 

 make a satisfactory open ditch. 



The scraper excavator is designed chiefly for digging very large 

 ditches or channels and does not appear to be suited for the type 

 of ditching usually required in anti-mosquito work. 



The last two types of trenching machines, therefore, are, 

 generally speaking, of value in anti-mosquito work only when the 

 use of tile drains on a large scale is contemplated or when a 

 very large excavation, as a new channel for a stream, is 

 required. 



Plows and scoops are usually drawn by horses or mules or 

 tractors. Almost all of them are lacking in any device for cutting 

 accurately to grade, thus requiring some hand-work to make the 

 bottom smooth. There are many types of these implements, 

 ranging from devices designed primarily to loosen up the earth 

 to quite elaborate machines that dig a V-shaped ditch up to 3 or 

 4 feet in depth. Two types of this class of machine are described 

 below. 



Wheel excavators supply their own power for digging and 

 traveling; this may be generated either by internal combustion 

 engines or steam engines and boilers. Many of the heavier 

 machines are equipped with apron tractors. The digging is done 

 by buckets upon the rim of a wheel that is revolved in the 

 trench, and, as each bucket reaches the top of the circle, the dirt 

 falls upon a conveyor belt, which deposits it on the spoil bank. 

 A shoe often follows the wheel, removing the crumbs and smooth- 

 ing and grooving the bottom. One machine of this type is 

 described below. 



