The Mosquitoes of New Jersey 227 



ter giving the best immediate protection possible, to accomplish the 

 largest possible amount of permanent draining and filling. In coun- 

 ties just beginning or in which the work has just recently begun, the 

 percentage of permanent work is bound to be high. This is espe- 

 cially true in counties having large and untreated marshes because 

 there is no hope of affording immediate relief in any other way. As 

 more and more of the permanent drainage work is done the oppor- 

 tunities for giving immediate protection to larger numbers of people 

 are increased through the extension of permanent work, and the 

 percentage devoted to temporary elimination will increase until such 

 a time as the permanent work has covered the area. 



Here again it should be pointed out that the geographical features 

 of each county are so different from those of other counties that 

 only the most general comparisons are justified. 



The acre cost of salt-marsh drainage and the acre cost of mainten- 

 ance in table 10 are particularly interesting. Unfortunately, 

 it has been impracticable from the data to determine the number of 

 feet of drainage per acre. 



Except in the case of Middlesex, where private and government 

 funds were used, the acre cost without doubt depends primarily 

 upon the footage installed and the difi^erences in acre cost are mainly 

 chargeable to that figure. Experience of the station has shown the 

 average acre cost of installing 300 linear feet of open salt-marsh 

 trenching is $5.00, reckoned on the basis of a ditch approximately 

 10 inches wide by 30 inches deep. 



The acre cost of maintenance depends, in open meadows, on the 

 number of linear feet per acre. On enclosed marshes the gain in 

 the absence of blockage by floating sod and rubbish is compensated 

 for by the lack of natural cleaning through the scouring action of 

 tidal suck, the charges for dike and tide-gate repairs and the appli- 

 cation of oil to mosquito-breeding in ditches. 



Here again it must be pointed out that the geography of salt 

 marshes varies to such an extent in different counties as to render 

 only the most general comparisons justifiable. 



Education in mosquito-control matters has proceeded from the 

 northern end of the coastal zone (an area extending from the coast- 

 line 30 to 40 miles inland) southward. Burlington has been found 

 to be particularly difficult to interest because the salt-marsh end of 

 the county is dominated by the western side where the salt-marsh 

 mosquitoes do not reach. Cumberland and Salem will naturally be 

 the last to be affected by the natural movement of this educational 



