144 MOSQUITO ERADICATION 



anchor by another steel cable, and the plant is drawn up to the 

 anchor. 



With a machine of this type and five men, it is possible to cut 

 3,000 feet of ditches a day, and, under favorable conditions, 

 sometimes more. Headlee 1 states that this machine cut the cost 

 of ditching from 2}4 cents a lineal foot in 1912 to less than 1>£ 

 cents in 1916. At that time, he states, the operating and 

 up-keep cost of ditching with this machine, as shown by cutting 

 hundreds of thousands of feet, did not exceed 1 cent a lineal foot. 



FILLING 



While the method of ditching outlined above is perfectly satis- 

 factory for the larger part of the salt marsh areas, there are 

 certain sections of marsh that cannot be successfully treated in 

 this way. There are areas which are so shut in by ridges, fills, 

 railroad grades and roadways, or so low-lying, that they may be 

 flooded by every storm or extra high tide and stagnant water 

 remain on them for weeks. Again, it may happen that on a 

 broad, open marsh, especially if the range of tides be small, 

 there are spots or pockets back near the upland too low to drain 

 by ditching. 



In such cases, the problem may be solved either by filling or 

 by diking and tide-gating. 



Filling is applicable only under certain circumstances. Thus, 

 it is too expensive for general purposes, and is used chiefly in 

 cases where the area to be filled is small, where it is very valuable 

 or where it proves to be the most convenient place for a dumping 

 ground. In making the fill, the trash should be smoothed down 

 and levelled in such manner that there will be no opportunity 

 for rain-water pools to form in it. 



DIKING AND TIDE-GATING IN GENERAL 



This is the accepted method of dealing with the areas described 

 in the last section. It should be recognized at the outset that 

 diking and tide-gating a given area is strictly an engineering 

 problem and that it should be handled as such. Failure to recog- 

 nize this fact may result in ineffective work and a waste of 

 money. 



1 "Some Recent Advances in Knowledge of the Natural History and the 

 Control of Mosquitoes," New Jersey Agricultural Experimnent Stations, 

 Bulletin 306, 1916. 



