496 REPORT OF OFFICE OF EXPERIMENT STATIONS. 



the plan operates successfully. The wells are usually not less than 

 9 feet deep and 3 by 4 feet in section, commonly curbed by plank, and 

 the outlet drains are laid about 4 feet deep, in the manner shown in 

 the figure. Three or four wells with their respective outlets will 

 sometimes drain 100 acres in localities where any number of tile 

 drains laid through the wet land in the ordinary way would prove 

 ineffective. 



STEAM LAND DREDGES. 



The methods so far described are those which pertain to drying 

 the field. Covered drains are always preferable except where the 

 volume of water becomes so great that they can not be used on account 

 of the cost. Open ditches must then be constructed where outlets 

 for large areas are required. The construction of such ditches 

 through land which has become seejDed and soft is often attended with 

 considerable difficulty, as well as is their maintenance after construc- 

 tion. The steam land dredge is employed, as other means for exca- 

 vating the ditches have been found impracticable where the ground 

 has become saturated to a considerable depth. The difficulty of 

 excavating such ditches emphasizes the wisdom of constructing the 

 necessary drains as soon as the need of them appears. A drag-line 

 bucket dredge which moves ahead of the excavated ditch is well 

 adapted to the work. (PI. XXV, fig. 2.) The platform upon which 

 the machine is mounted is moved on rollers or on skids ahead of the 

 ditch as it is excavated. Ditches about 8 feet deep, and located so 

 that all drains within the area to be restored can be discharged into 

 them, are a necessary part of the reclamation of any large area of 

 seeped lands. (PI. XXVI.) 



MAINTENANCE. 



Constant attention will be required to maintain open ditches in 

 proper condition. They are subject to obstruction by the accumula- 

 tion of Russian thistles and other weeds which the wind carries into 

 them, and to filling by soil which is washed from the adjoining lands 

 by waste water, when the fields are irrigated. Covered drains must 

 also receive attention in soils which do not become compact and firm 

 over the drain, for the reason that whenever the land is irrigated 

 water will quickly find its way into the drain, carrying with it an 

 amount of soil which will soon fill and obstruct it. This inconvenience 

 and risk disappears as the earth with which the trench is filled be- 

 comes compacted, which condition is hastened if special care is taken 

 in packing the earth at the time the trench is filled. Attention to the 

 many details of construction and maintenance which can not be 

 enumerated here are required in draining irrigated fields. 



