132 N. J. Mosquito Extermination Association 



be cleaned ; and in varying proportions in the different counties the 

 drainage of the meadows is changing from a ditch-digging to a 

 ditch-cleaning proposition. 



Before describing the development of a machine to clean ditches 

 it may be well to illustrate the importance of cleaning them. In the 

 Hackensack and Newark Bay salt marshes in the northeastern part 

 of New Jersey a large proportion of salt marsh is protected from 

 the inflow of high tides by dikes and tide-gates. It is to these diked 

 areas that the following illustration applies. 



There is a vast difference between ditching a meadow and drain- 

 ing a meadow. Figure I shows a meadow which has been ditched, 

 but it is plain to be seen that it is not drained. Figure 2, on the 

 contrary, shows a similar meadow area in which the ditching has 

 drained the meadow. The significance of this difference is better 

 illustrated by Figure 3, which represents a vertical section through 

 a portion of the salt marsh. Grass is growing on top of the sod or 

 peat, which latter averages about 18 inches deep. Below the sod is 

 the meadow mud. To the right is shown one of the drainage ditches, 

 usually ten inches wide and varying in depth from 24 to 30 inches. 

 To the left is a hole or depression in the meadow surface, one of 

 many thousands, which hold water for a longer or shorter period, 

 depending on the rainfall, evaporation and drainage. These holes, 

 if wet for a long enough period, will incubate a brood of mosquitoes. 

 Because of the uncertainty of depending on evaporation to dry out 

 these holes it is necessary, in order to control mosquito breeding, 

 to provide other means of removing the water. Sometimes this is 

 done by digging a small ditch, commonly called a spit, from the hole 

 to the drainage ditch, but in many cases it is necessary to depend 

 upon the seepage of the water from the hole through the sod to the 

 drainage ditch. In either case it is very evident that the water in 

 the drainage ditch must be at a lower level than the bottom of the 

 hole. Just what this level should be is a matter now under con- 

 sideration by the Committee on Standards, but for purposes of 

 discussion a tentative value of 18 inches below the meadow surface 

 has been agreed upon. 



It does not take much argument to show that if the water in the 

 ditches is to be kept down to 18 inches below the meadow surface, 

 the ditches themselves must be clean and free for the flow of water 

 to a depth of more than 18 inches. This means frequent cleaning. 

 To do this by hand is very expensive. The great need of ditch clean- 

 ing machinery in order to reduce the cost has been recognized for 



