126 



MOSQUITO ERADICATION 



ditch. The lining of the bottom and sides up to 3 or 4 inches 

 above the normal water line generally will answer for small 

 ditches. In wide ditches, the bottom should slope toward the 

 center and the side walls may often be nearly vertical. 



Fig. 85. — Openjiitch lined with concrete. 



A smooth or fancy finish, which adds to the cost, is not essen- 

 tial. The ditch may be lined roughly with flat stones, the holes 

 being chinked up and mortar plastered "about ]them. Where 



Hzm" 



( Ho jtfied offer iefripce) 



Fig. 86. — Cross-section of lined main ditch and unlined lateral. 



flat stones are not available, a 2-inch layer of concrete, reinforced 

 with chicken wire of about 2-inch mesh may be used. 

 LePrince continues: 



