23 



It has been recognized for some time by the men engaged in 

 the work that the most elaborate systems of ditches will some- 

 times fail to prevent the maturing of mosquitoes, and it was 

 also recognized by Prof. Smith, for, in his report of 1905, he 

 states : 



"I have spoken of mosquito control rather than extermination 

 because I do not believe actual extermination is possible in the 

 case of an insect that develops so rapidly and in such a great 

 variety of places. There will always be careless people and 

 there will often be unusual seasons that will give mosquitoes a 

 chance to maintain themselves ; but it is quite within our power 

 to deprive them of their larger breeding areas and to reduce 

 them to a point where they will cease to be obnoxious. Im- 

 provement of the salt marsh conditions will prevent the migra- 

 tions and will enable communities to benefit by their enterprise 

 in improving conditions." 



To meet these unusual seasons and conditions an effort has 

 been made to fortify the ditching systems by means of dikes 

 and tide-gates where meadows are low or tides are slow in 

 running off. By means of the dikes the high tides are kept 

 from overflowing the meadows, and the tide-gates are so con- 

 structed as to permit the water to flow out of the streams on 

 the ebb tide, but close automatically when the tide starts to rise. 

 In this way the water level in the ditches is kept constantly low, 

 permitting them to give constant seepage action. The surface 

 of the meadow is also kept dry and in condition to soak up the 

 rains. 



This system of tide-gates and dikes to supplement the drain- 

 age systems is by far the best protection within our means, with 

 the exception of filling in, but it is unfortunately far too ex- 

 pensive to be carried out universally at present. It does not 

 decrease to any extent the number of feet of drainage ditches 

 needed, and the cost of the tide-gates and dikes is therefore 

 additional to the cost of initial drainage. It has been carried 

 out successfully in the northern part of the State, where the 

 meadow areas are smaller, but it is impracticable in South Jersey 

 except under unusual conditions. 



