i65 



In the early days of the work there were no precedents on which 

 to proceed. The question of the best width for ditches and how 

 deep to dig them was a moot question. Careful investigations 

 of the tidal conditions showed that mean high tide rises from six 

 inches to a foot below the surface of the salt marsh, and the grass 

 roots of the sod extended from 12 inches to 18 inches below the 

 surface. It was, therefore, decided that it would be well to dig 

 the ditches at least two feet deep, so as to cut below the grass roots 

 and insure a flow of fresh water in the ditches at each side. At 

 first the ditches were dug quite wide, but experience has shown 

 that when a ditch is wide enough for the sun to reach the bottom 

 there is a tendency for the grass roots to again start growing, and 

 thus in timie close the ditch. As a consequence, most ditches are 

 now dug 10 inches wide and 24 inches deep. Main canal ditches 

 are, of course, dug as wide as may be required to carry off the 

 water from the ditches connected thereto. I am a firm believer in 

 the usefulness of a marginal ditch and in intersecting ditches 

 where such can be placed without detriment to property interests. 



It must not be assumed that the present effective methods of 

 drainage were always in vogue. Mosquito drainage work has 

 evolved rapidly from the first crude ditches dug at Rumsens Neck 

 about 1903, with ordinary spades, to the splendid straight, 

 smooth-sided ditches now cut with tools especially designed for 

 the purpose, and which my experience shows will stand up and 

 be effective for many years. 



The methods now used in New York State have been, with a 

 few modifixations, adopted in every state where mosquito elimi- 

 nation by drainage is practiced. 



The porous nature of the salt marshes is what makes the drain- 

 ing method of extermination so successful. In some cases the 

 draining power of a ditch will reach approximately one hundred 

 and fifty (150) feet, although seventy-five (75) feet is a good 

 drainage distance; therefore, if the ditches are spaced one hun- 

 dred and fifty (150) feet apart the entire surface of the marsh 

 land will generally dry out quickly. This, of course, is only a 

 general rule and unusual conditions will cause variations. In 

 places where natural streams or creeks are not available it becomes 



