SPECIAL FARM TOPICS 269 



useful in experimental drainage where the doubtful results of the 

 experiment did not seem to warrant the use of more expensive ma- 

 terial. They are made in rectangular form, with or without bot- 

 toms, according to the ground in which they are to be used. 



The use of the open-bottom box, or tile, as an intercepting drain 

 is of little or no value in gravel formations, especially where the 

 surface slope is considerable. In the relief system the drains must 

 be placed nearly parallel to the direction of flow of the ground 

 waters, and the best results are secured when thus laid. More or less 

 satisfactory results will be secured when the drain runs slightly 

 oblique to the direction of the flow. The more nearly the line of the 

 drain approaches a direction at right angles to the flow of the ground- 

 waters, the less efficient will the drain prove. (F. B. 187; Kept. 

 Office Ex. Sta. 1910; Mont. Ag. Col. B. 76.) 



Bogs. The cultivated areas are frequently bordered on one or 

 more sides by lands in which the shale is partially disintegrated and 

 which convey the water from the higher irrigated land, or possibly 

 from irrigating ditches, into the soil blanket, where it fills up the 

 land so completely as to make a permanent bog. Not infrequently 

 it is entirely impracticable to place a drain through the wet part of 

 the field because of its extremely soft and unstable condition. At 

 least a part of the water must be intercepted and prevented from 

 entering the field before complete drainage can be effected. This is 

 accomplished by placing a drain on the edge of the wet tract in such 

 a way as to penetrate the shale which delivers the water. (Mont. 

 Col. Bui. 76.) 



Maintenance. Constant attention will be required to main- 

 tain open ditches in proper condition. They are subject to obstruc- 

 tion by the accumulation of 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 ir- 

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

 it an amount of soil which will soon fill and obstruct it. This in- 

 convenience and risk disappears as the earth with which the trench 

 is filled becomes compacted, which condition is hastened if special 

 care is taken in packing the earth at the time the trench is filled. 

 (Kept. Office Ex. Sta. 1910; F. B. 371.) 



Seepage. There are thousands of acres of some of the best 

 agricultural lands in the Northwest becoming less productive be- 

 cause of the excessive moisture of the soil occasioned by seepage. 

 The cause of seeped or oversaturated land is the waste from irri- 

 gation and leakage from canals and laterals. The skillful irrigator 

 may insist that if no more water is applied than is needed for grow- 

 ing and maturing the crops, and that if the canals are so constructed 

 that no substantial amount of water escapes into the earth, no land 

 will become too wet for farming purposes. It is true that in many 

 instances irrigators have been unduly prodigal in the use of water, 

 particularly when the land is first subdued and watered. The art of 



