tends to pile up more or less at the end of the bog where the 

 water is admitted. The marginal ditch should be 3 or 4 feet 

 wide and 2 feet deep. One of its purposes is to prevent upland 

 growths from encroaching on the bog. It also prevents many 

 kinds of insects from crawling on to the bog, and it is a con- 

 siderable protection in case the bog is threatened by forest 

 fires. It is customary to have one of the cross ditches larger 

 than the others and running lengthwise of the bog, in the path 

 of the direct flow of water from the brook or reservoir used for 

 a w^ater supply to the drainage outlet. This is desirable, as it 

 accelerates the handling and distribution of the water in flood- 

 ing and draining. Such a ditch is especially desirable on bogs 

 of large area. 



Grading. 

 All single bog areas should be as nearly level as possible, so 

 that they may be flooded quickly and with as small a quantity 

 of water as possible. The grading is done after the ditches are 

 dug, the water line in the ditches being used to grade from. 

 If the water supply is very abundant, it is not so necessary to 

 be particular about getting the bog surface level as it is if the 

 supply is scanty. The material thrown out in ditching may be 

 used to fill up the holes formed by the pulling out of stumps or 

 otherwise. Usually it is profitable in the long run to spend 

 considerable money and effort in getting a bog perfectly level, 

 and no swamp ought to be selected for cranberry purposes 

 where it is impossible to perfect such grading at a reasonable 

 expense, unless the water supply is ample. 



Dikes. 

 The dams made for holding the water in reservoirs and bogs 

 in flooding are of the sort called dikes. They are usually made 

 of a wide core of sand faced on either side with a wall of turf. 

 This turf may often be gathered from the upland surrounding 

 the bog, but the surface of the swamp itself usually has to be 

 scalped" after the lumber and brush are removed, and the turf 

 thus obtained may be partly or wholly used in facing the dikes 

 and in walling the ditches. Unless certain malignant weeds 

 are present to cause trouble, this turf need not, however, be 

 removed from the surface of the swamp unless it is needed for 



