INLAND DRAINAGE 107 



To comply with the first principle mentioned, the main ditch 

 should, in all cases, be constructed first. Frequently it will be 

 found that laterals, which appeared to be needed before the main 

 ditch was dug, will not be required at all. If there is any doubt 

 as to the need for a lateral, it should not be dug. 



In regard to the second principle, it may be suggested that, in 

 average soils, the slopes of the sides of the ditches should be 

 about 45 degrees; in sand and soft mud, the slope may be flatter, 

 while, in hard clay and rock, it may be almost vertical. The 

 bottoms should be made narrow so that, when the flow is small, 

 the water will have no opportunity to spread out and form pools. 

 Straightness of course, where the ditches are not laid out by 

 instrument, may be attained by use of a line, where necessary. 

 Branch ditches should join main ditches at acute angles or curves, 

 in order to lessen depositing of silt, sand, debris, etc., at the 

 junction point. 



HAND DITCHING ON FIRM GROUND 



Most anti-mosquito ditching is done by hand, probably 

 because most projects are too small to justify the purchase of 

 machinery. However, when machinery is available, it should 

 be used wherever practicable. 



The chief tools needed for hand ditching are picks and shovels. 

 Where the earth is full of roots, a mattox will come in handy. 

 A tiling spade may be used for finishing off the bottom. Some- 

 times a hoe will prove valuable. The phosphate drag, a tool 

 somewhat resembling a potato-hook, only heavier, is useful 

 for cleaning out ditches or for general work in marshy land that 

 is full of roots. 



In cutting ordinary ditches by hand, no great technical skill 

 is necessary. Common sense and ability efficiently to handle 

 men are the chief requisites. Upon beginning work, the ditch 

 should be laid out by means of lines, so that it will be dug straight. 

 The men then should be scattered out along the lines, a section 

 being allotted to each team of two men. As each team finishes 

 its section, it should be moved forward and given another section. 



Constant vigilance is essential to see that the men keep the 

 bottom even — that is, avoid alternate humps and depressions. 

 Probably the best way to do this is to select two or three intelli- 

 gent men and assign them the job of finishing the bottom of the 

 whole ditch. 



