5 



Over the great part of the tract the drains were laid at a depth of 

 4 feet. In that part nearer the lake a somewhat shallower depth was 

 necessitated in order to obtain a gravity outlet for the drainage water. 

 The drains were laid on a grade of not less than one-tenth foot in 100 

 feet, except where 3-inch tile was used when the grade was somewhat 

 higher. The illustration (fig. 1), is a plan of the completed S3 7 stem, and 

 shows the supply canals, position of the weirs, drains, and the position 

 and extent of the different sizes of tiles. The system as installed has 

 proven adequate. Flooding has been carried on systematically, the land 

 being divided into checks and plats by levees, and each plat treated in 

 rotation. During each flooding water has been added to an life rage 

 depth of 4: inches. The movement of the water into the soil has been 



ca-naL. 



FIG. 1. Plan of drainage system, Swan tract. 



regular, and, considering tlie character of the clay subsoil, rapid, and 

 the drains have quickly filled after the floodings and have run freely 

 throughout the experiment. 



During the last season (1903) the land was flooded once each week, 

 with occasional longer intervals when the supply canal was being 

 repaired or during times when the land was being plowed or the levees 

 repaired. 



Before any water was applied to the tract a detailed survey was made 

 to determine the alkali content of the soil. This initial survey was 

 made in September, 1902. The land was then flooded once and allowed 

 to remain until the next spring. 



