128 Mosquitoes 



from the surrounding soil, and, especially if close to 

 high tide, dry so slowly as to give ample time for 

 development. A large, single, depressed area in an 

 otherwise safe space is best converted into a per- 

 manent pool at least two and one-half feet deep, 

 stocked with killies. A shallow pool would soon fill 

 up with vegetation, becoming a good breeding place. 

 Sods should never be left where they can fall in the 

 ditches, but are useful in filling up holes. If a marsh 

 can be burnt over, it seems to drive the mosquitoes 

 off the next season, and also to promote the levelling 

 and drying of the land. 



Ditching may be accomplished by hand or by a 

 machine. In extensive work, machine ditching, 

 which should cost little over one cent per running 

 foot, or perhaps one and one- half if sods are 

 to be removed and holes filled in, is cheapest. 

 Hand ditching costs one and three-quarter cents 

 at the highest. On the Newark meadows the 

 "True ditcher" is used, cutting from 3000 to 4000 

 feet of ditch two feet deep and from six to twelve 

 inches wide per day. Long, narrow steel spades are 

 used in hand ditching ; square-edged, to cut the 

 sides; curved, and a little grooved, to level the 

 bottom. Ditch bottoms should be level and outlets 

 wide. 



Where there is much sand, ditching is ineffective ; 

 in such places and in swamps with no outlets, situ- 

 ated among sandhills, filling is the only remedy. 

 The large areas must be filled by hydraulic dredges, 

 which process costs fifteen cents per cubic yard — 

 an expensive method. 



