ii6 AGRICULTURAL EXPERIMENT STATION. 



eighteen-inch sod they will last well ; but the tendency is to fill 

 and choke and they will need constant looking after. 



Taking the marsh area as a whole there is a very good natural 

 drainage in most sections by means of ''Thoroughfares" and 

 "Slews," to which artificial, ditch drainage can be led. It will 

 prove surprising in many localities to find how little work is 

 actually needed to remedy serious conditions. 



First and most important then of the methods of dealing with 

 the marsh mosquitoes is such drainage as will prevent the for- 

 mation and maintenance of shallow pools by extra tides or heavy 

 rains. The drainage need not be such as will make the land suit- 

 able for agricultural or other practical purposes, except possibly 

 for salt hay, and it need not be so extensive as to completely drain 

 the land with the retreat of the tide or the cessation of the rain ; 

 but it must be sufficient to remove all surface water within forty- 

 eight hours. 



Over a large marsh area the ditches will be all that is neces- 

 sary, because the depressions are shallow, rarely holding over 

 four inches of water when completely filled. Where the holes 

 are deeper, as they sometimes are, they must be filled with the 

 sods taken from the ditches unless they are so large as to main- 

 tain fish continuously. At a depth of twelve inches a hole or 

 depression itself acts as a drain from the surrounding territory, 

 and if at all close to the ordinary high tide level, the last few 

 inches will disappear very slowly, giving ample time for the 

 brood to develop. I have seen sometimes a pool of this kind 

 reduced to an area of three or four square feet and so crowded 

 with larvae and pupae that it seemed as if there could not possibly 

 remain space for even one more. Sods should always be removed 

 from the immediate edge of the ditch to prevent their falling 

 in or being floated in by a high tide and, so far as they go, they 

 may be used to fill up even the shallower holes and depressions. 

 Occasionally it happens that there is a depressed area in an 

 otherwise safe meadow at a considerable distance from any 

 natural watercourse, and in such a case converting it into a per- 

 manent salt pond with steep banks is the best method of dealing 

 with it. Such a pond should be at least two feet six inches deep 

 and should be stocked with killies from the nearest natural water- 

 course. Other marine life will come in with the spring tides and 

 a dangerous breeding area will be made safe. No vegetation will 

 start in the bottom of such a pool, but a shallower one would 

 soon become obstructed and dangerous. The material removed 

 from the pond may be used in filling at points nearby, or in 

 lessening the extent of the area to be excavated. Very fre- 

 quently slight depressions or small holes can be wiped out by 



