DRAINAGE OF SALT MAESHES 393 



quitos by relatively simple and comparatively inexpensive ditching operations. 

 The annual expense is only about $1000 and the total expenditure on these 

 operations during the past four years does not exceed $10,000, in spite of the 

 fact that the village is situated upon a narrow neck of land with the extensive 

 salt marsh areas of Jamaica bay to the north and west and large marshes south 

 and east, all producing in former days millions of mosquitoes which invaded 

 the village in swarms with every favorable breeze. Some of these marshes extend 

 almost to the center of the village, which is so completely surrounded that a 

 journey of 2| miles in almost any direction will bring one to a salt marsh. More 

 unfavorable conditions for mosquito control could hardly be found, and before 

 this work was attempted mosquitos swarmed in the village in May and remained 

 in numbers most of the season. The second year swarms did not invade this 

 territory till June, and last year it was the first of July before they appeared. 

 Our investigations at the end of last July showed that there were practically 

 no mosquitos in the center of the village. It was our privilege to sit on a piazza 

 one evening when conditions were most favorable for mosquito activity. Though 

 it was cloudy with only a little breeze and rather warm, not one appeared. 

 Previous to this antimosquito work it was said that one could not sit on this 

 piazza without being covered by netting, and the owner even went to the 

 trouble of making a framework to hold netting suspended over individual chairs, 

 so that his family and guests could sit in comfort. 



" This very desirable result has been brought about by a drainage system so 

 planned that the entire length of all ditches will be flushed by every tide. 

 The general practice is to run these ditches within about 200 feet of firm ground 

 and sometimes closer, making them 18 to 24 inches in width, from 2 to 3 feet- 

 deep, with main ditches here and there to tidal channels. A few headland 

 ditches are run into the more dangerous swampy areas in baylike extensions of 

 the marsh. Such ditches require no surveying and cost only 1^ cents a running 

 foot. A little experience enables one to lay them out properly and the tides make 

 the determining of levels extremely easy. It was very interesting to compare 

 the conditions between ditched areas and undrained marshes. The former were 

 so free from mosquitos that one could tramp upon them with practical im- 

 munity from bites, though occasionally a few mosquitos were seen on one's 

 person. No larvae were found and in fact there were very few places where 

 breeding was possible. Undrained marshes presented a very different condition. 

 Mosquitos swarming in adjacent woodlands made driving very uncomfortable, 

 and when on the marshes one was attended by considerable swarms of vicious 

 biters, even in midday. Here and there breeding pools were literally black with 

 young wrigglers. This contrast between drained and undrained areas would 

 doubtless have been much greater were it not for the fact that our inspection 

 was made during such a dry time that even undrained marshes presented com- 

 paratively few favorable breeding places. 



" Experience at Lawrence has shown that deep ditches with perpendicular 

 sides are far more permanent than shallow ones with sloping sides. The attempt 

 to slope the bottom of the ditch so that all the water will drain out invariahly 

 results in depressions which may become dangerous breeding places and the 

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

 tunity for the growth of grass and sedges with the result that the ditch soon be- 

 comes 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 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 



