THE IRRIGATION AGE. 



207 



DRAINAGE OF FARM LANDS. 



Results of Careful and Extended Investigations by the Gov- 

 ernment for the Benefit of the Farmers. 



BY <j. G. ELLIOTT, 

 Expert in Drainage and Irrigation, U. S. Department of Agriculture. 



From Farmers' Bulletin No. 187, Courtesy U. S. Department of 

 Agriculture. 



in making them, every particle should be completely 

 burned. Such a tile is then almost indestructible in 

 earth and water. Where exposed to long-continued 

 freezing and thawing, as at the outfalls, the best vitri- 

 fied pipe should" be used. After one has become fa- 

 miliar with the ware of a particular factory, properly 

 burned tiles may be readily distinguished by their color 

 and by their ring when struck with a piece of steel. 

 Good clay may usually be semivitrified if skill is used 

 in burning. Porosity of the finished ware is not impor- 

 tant, since the quantity of water that will pass through 

 the walls of well-burned tile is practically nothing. All 

 water enters at the joints. Vitrification, although not 

 essential, is always a desirable quality in drain tiles. 



DEPTH AND DISTANCE APART OF DRAINS. 



To secure efficient drainage the individual lines 



(CONTINUED.) 

 UNDERDRAINAGE. 



The history of drainage shows that a great variety 

 of methods and materials have been employed in the 

 work, many of them effective and all of them aiding to 

 demonstrate its usefulness in agriculture. 



USE OF TILES. 



The use of drain tiles for this pur- . i=< 



pose, introduced in England about the \ 4^-f-"-- - 



year 1810, has increased to such an ex- 

 tent and the art of using them - has 

 been so perfected that the tile-drain is 

 now regarded as the best type of un- 

 derdrain. Well-burned clay pipes of 

 circular form, one or two feet long, 

 are laid through the soil in a continu- 

 ous line upon such a grade that any 

 water which .finds its way into them 

 will be carried by gravity to some 

 lower point, thus conveying the sur- 

 plus away. The water enters the line 

 of tiles through openings left between 

 the ends, or "joints," as they are com- 

 monly- called. The ends of the tiles 

 should be placed close together in or- 

 der to prevent the soil from entering, 

 yet not so close as to prevent the en- 

 trance of water. The action of the 

 tile-drain in removing the surplus 

 water from the soil is as follows: 



The drain being surrounded by 

 soil the spaces of which are filled with 

 water, the water in the soil flows by 

 gravity through the crevices between 

 the ends of the tiles, thus entering the 

 drain, and passes off more or less rap- 

 idly, according to the grade upon 

 which the line is laid. Other water of 

 the soil takes the place of that re- 

 moved, the water of saturation gradu- 

 ally passing from the surface down- 

 ward, the soil near the level of the 

 drain being the last to be relieved. 

 The water moves downward and lat- 

 erally toward the drain, and the lateral 

 distance to which the drain will relieve 

 the soil of water is governed by the re- 

 sistance which the soil particles offer 

 to the flow of water among them. This 

 process does not leave the soil without 

 moisture, but only removes the sur- 

 plus. It does not, however, remove it 

 from points below the level of the drain. 



KINDS OF TILES. 



The tiles used should be round in form, straight, 

 and above all well burned. They need not be vitrified 

 in order to be lasting, but whatever kind of clay is used 



Fig. 9. Map showing the drainage of 480 acres of land in Iroquois County, 111., on which 

 69,700 feet of drain tile were laid three and four feet deep. 



should be placed sufficiently near to each other for the 

 effect of one line to reach that of another on either side 

 so as to bring all the soil within the active range of the 

 drains. The distance apart will depend upon the close- 

 ness of the soil, or, in other words, upon its retentive 

 character. Soils are spoken of as "open" or "close" 



