Proceedings of Eighth Annual Meeting 113 



drainage only. The initial cost of tide-gate and dike construction 

 is more than open ditching, but it has the advantage that areas so 

 diked can be inspected at any time regardless of the tide and the 

 water table at all times is at a much lower level than in open ditches. 

 It has this distinct disadvantage, that the water in the ditches has a 

 very sluggish motion and breeding is likely to occur in the ditches 

 themselves. If possible, in designing a closed ditching system, pro- 

 vision should be made to obtain circulation of the water by opening 

 all tide-gates or certain of them at fixed periods. This flushes out r 

 the ditches and lets the fish into the diked area where they can help 

 keep down the ditch breeding. 



The use of pumps in clearing areas of mosquito breeding is not 

 as yet very general. Yet there is much to be said in favor of it. 

 On some areas, natural conditions are such that gravity drainage 

 even aided by tide action cannot move the water away from an area 

 fast enough to prevent the emergence of a brood. The practical 

 method then is to make use of auxiliary means of pumping to sup- 

 plement nature. Although the initial cost of a pumping unit is com- 

 paratively great, it furnishes the means of moving water away from 

 an area faster and more completely than any of the other methods 

 and certainly is a most active ally in times of storm. So often drain- 

 age systems which are apparently all right under ordinary circum- 

 stances will break completely under exceptional conditions and a 

 large brood will escape in mid-summer because of the failure of this 

 system. Such a brood on the wing will discount the work of months 

 and often do much to discredit an entire season's patient labor. If 

 mosquito control is to be ultimately accepted, such extraordinary 

 working conditions must be expected and successfully handled. For 

 emergency times, there is no system so dependable as. a pump and it 

 is probable that as our knowledge of drainage for mosquito control 

 broadens, pumps will be used more and more. And in placing 

 pumps, it must be kept in mind that a pump can only take water 

 which is brought to it and proper reservoir ditches are most impor- 

 tant. 



So much for the types of mosquito control drainage on the salt 

 marsh. On the upland, the task differs from that on the meadows 

 because here there is no tide action to be considered. With this 

 exception, however, the problem is much the same and there is the 

 same necessity for thorough and intensive study of each place 

 before attempting drainage. And here again the size, shape and 

 general location of the swamp or pool to be drained, the rain-fall and 



