906 IOWA DEPARTMENT OF AGRICULTURE. 



along some cut-off than along the line of natural overflow. But the 

 principle holds that efficiency and economy in construction are based 

 upon locating drains along the lines of natural drainage. 



The laterals should be placed up and down the slope. This rule ap- 

 plies not only to hillsides which require drainage, but also to flat land 

 which has but a slight slope. A goodly number of laud owners advocate- 

 placing lateral drains across a slope. This plan is favored on the ground 

 that the water coming from the soil above is intercepted by the tile- 

 drain and is thus prevented from rendering the soil below the drain. 

 wet and unproductive. "Practice has proven this to be a mistake," says 

 C. G. Elliot, the eminent drainage authority. He says in addition, "Lines 

 for conveying the drainage-water may be located at right angles to the 

 slopes if placed so far down on the bottom land that the grade of the 

 drain is greater than the slope of the surface at the side. Water oozes 

 through the soil along the line of steepest descent, at all times seeking a 

 iDwer place where it can be at res". If a drain is placed acro-s his 

 course of soil water, the descent of the soil channels being greater than 

 that of the drain, water will flew out of the joints of the drain and con- 

 tinue to ooze through the soil, only a small part being conveyed away by 

 the drain. 



It is well to note the following exceptions to the rule that drains 

 should be laid up and down the slope. W^hen a pond or swamp is sur- 

 rounded by steep slopes whicli have a porous subsoil the water tends 

 to flow through this porous stratum to the base of the slope and accumu- 

 late there, thus forming an exceedingly wet area around the border of 

 the pond or swamp. Because of the fact the soil of the wet area border- 

 ing the pond is less previous to water than the subsoil of the slopes, it 

 is kept constantly saturated and a line located in the center of the pond 

 does not adequately drain this wet border. In such a case the remedy 

 is found in an intercepting drain laid near the base of the slope. 



Again, there are extensive swampy areas which receive a constant 

 supply of seepage water from steep side slopes. This water should be 

 intercepted by drains at the upper edge of the saturated strip. 



Wherever it is possible, long, parallel laterals should be used. This 

 is chiefly in the interests of economy. Lands is doubtly drained where- 

 ever one drain joins another as in the case of a lateral making a junc- 

 tion with a main or submain. There are instances where the lay of the 

 land is such that short laterals are necessary. 



There is another point in regard to locating drains which is worthy 

 of emphasis. On level areas where the grade is necessarily light, great 

 care should be exercised not to overcharge mains. This mistake is easily 

 made when there is a large area to be drained and the grades are light 

 for both mains and laterals. 



In board, flat sloughs it is often advisible to use two lines of tile 

 instead of one large main through the center. When this is done the 

 collecting drain should be located near the base of the slope. The advan- 

 tage is this: By this arrangement it is not necessary to carry laterals 

 down the slon«= and for some distance through a flat bottom which would 



