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high to run off the water completely. It is seldom that such 

 outlets as are found already placed are suitable for mosquito 

 extermination purposes. It is not advisable to rely upon them. 

 The more satisfactory procedure is running a set of compara- 

 tive levels before a job is done. If this is done it is surprising 

 what apparently inaccessible places can be drained. 



No ditch, however carefully planned and excavated, will func- 

 tion indefinitely without attention. This means systematic main- 

 tenance work each year. The entire drainage system should be 

 overhauled. The amount of maintenance work to be done act- 

 ually grows less as time goes on, for after several years of thor- 

 ough drainage, swamps, both woodland and open, tend to lose 

 their swampy nature. The soil becomes hard and firm and the 

 character of the vegetation changes considerably. As a result 

 the laterals may be permitted to disappear and only the main 

 ditches need be maintained. To get the full benefit of this per- 

 manent work, all ditching, both cleaning and new digging, should 

 be completed before it becomes necessary tO' oil. The resulting 

 saving in the cost of oil and labor is considerable. It is well, 

 however, to have a man or two available for odd jobs during 

 the entire season, as it is often necessary to repeat some of the 

 work. This is particularly true in pasture lots where the ditches 

 are trampled shut by horses or cattle, and near communities 

 where the ubiquitous small boy finds his greatest pleasure in 

 building dams in ditches and streams. 



Where the topography of the land makes draining impossible, 

 and it is impractical to fill, swamps and pools may sometimes be 

 drained by opening up the subsoil with dynamite. This was 

 undertaken in Essex County, and the following spring it was 

 noticed that no breeding took place in several of the woodland 

 pools that had failed to drain. The explanation probably is that 

 the eggs were destroyed by the shock of the explosion. This 

 suggests an interesting line of experiments to determine whether 

 spring breeding in otherwise inaccessible woodland poolsi and 

 swamps may not be prevented by dynamiting. 



While the actual finding and destruction of mosquito breeding 

 is the sine qua non of the work of extermination, these opera- 



