114 NEW YORK STATE MUSEUM 



Experience at Lawrence has shown that deep ditches with per- 

 pendicular sides are far more permanent than shallow ones with 

 sloping sides [see pi. 8-10]. The attempt to slope the bottom of 

 the ditch so that all the water will drain out invariably results in 

 depressions which may become dangerous breeding places and the 

 drainage value of the ditch itself is much lessened. Sloping sides 

 [pi. 10, fig. 2] afford opportunity for the growth of grass and 

 sedges with the result that the ditch soon becomes choked with 

 vegetation. The deep perpendicular ditches described above remain 

 entirely free from vegetable growth, and with a little care in 

 removing sods and drifting matter will last for years. Some dug 

 four years ago [pi. 9, fig. 2] were in perfect condition last July, 

 though the grass growing along the sides overhung and almost hid 

 the ditch from view in places. An area of 25 feet on each side is 

 easily drained by such a ditch. The village now has 40 miles of 

 marsh drains which require more or less attention from three men 

 during most of the open season. They keep the ditches clear, 

 supplementing their work by judicious oiling here and there wher- 

 ever mosquito larvae are abundant and then have considerable time 

 available for perfecting the system and ditching more distant 

 marshes. Experience showed that a considerable number of salt 

 marsh mosquitos bred on that portion of Jamaica bay northwest 

 of the village were brought in by southwest followed by northeast 

 winds. This led to the extension of ditching operations some 2 

 miles beyond the village limits. The work in the immediate vicinity 

 of Lawrence was done partly at public expense assisted by contri- 

 butions from owners benefited, though it was impossible to secure 

 the cooperation of persons owning the distant marshes, which latter 

 were drained entirely at village expense. The existence of such 

 breeding areas is an imposition upon adjacent communities and it 

 is only a question of time before public opinion will demand a law 

 either compelling owners to abate such nuisances or else provide 

 for their suppression at public expense. The money invested by 

 Lawrence in this work, a total of less than $10,000, has amply 

 justified itself in vastly improved conditions. The village and its 

 vicinity have been entirely freed from breeding places, though 

 occasionally it is subject to late summer invasions by hordes of 

 mosquitos when favorable winds bring them from und rained 

 marshes. Even this will be obviated when the value of the work 

 becomes more generally appreciated and then the cost of the oper- 

 ations will be amply returned in increased land values, to say 



