DRAINAGE MEASURES. 43 



A great deal of valuable drainage work has been done in the past 

 few years in the salt marshes of the North Atlantic coast, and there 

 is one instance of this on the Pacific coast, with the direct idea of 

 doing away with the salt-marsh mosquitoes, several species of which 

 occur in such localities, all having unusual power of flight and being 

 able to proceed inland for many miles, thus annoying the inhabitants 

 of a large extent of country. One of the first operations of this kind 

 was conducted by the wealthy owners of Center Island, off the north 

 coast of Long Island, in Long Island Sound. This work led to the 

 somewhat elaborate work under the organization known as the 

 North Shore Improvement Association, referred to elsewhere, which 

 included simple operations over a considerable distance along the 

 north shore of Long Island and in the vicinity of Oyster Bay. These 

 operations took place in 1902 and 1903. Later some excellent work 

 was done at Lawrence, Long Island, and the following account, taken 

 from the '"Report of the New York State Entomologist," Dr. E. P. 

 Felt, for 1905, gives an excellent idea of methods and results: 



A most striking illustration of this work is that given by Lawrence, L. I., which has 

 amply demonstrated the feasibility of controlling the salt-marsh mosquitoes by rela- 

 tively simple and comparatively inexpensive ditching operations. The annual 

 expense is only about SI, 000 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 mosquitoes 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 mosquitoes 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 antiniosquito work it was 

 said that one could not sit on this piazza without being covered with netting, and the 

 owner even went to the trouble of making a framework to hold netting to suspend over 

 individual chairs, so that his family and guests could sit in comfort. 



This very desirable result has been brought about by a draining system so planned 

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

 practice is to run these ditches within about 200 feet of linn ground ami sometimes 

 closer, making them I s * to - 1 inches in width, from 2 to \\ 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 H cents a running foot. A little experience enables one to 

 lay them out properly and the tides make the determining of levels extremely 

 It was very interesting to compare the conditions between ditched areas and undrained 

 marshes. The former were BO free from mosquitoes that one could tramp upon them 

 with practical immunity from bites, though occasionally a few mosquitoes we* 

 on one's person. No larvae were found, and in fact there were very few places where 



