Plate viii. Mosquito control on salt marshes, top. Constructing main outlet 

 ditch on enclosed salt marsh with caterpillar crane equipped with three- 

 eighths cubic yard dragline bucket. Similar machines are used for upland 

 drainage and for constructing dikes and tide gates on salt marshes, bottom. 

 Spraying with mosquito oil a main drainage ditch on a diked salt marsh so 

 heavily sewage-polluted that fish cannot live in it. 



