GROUND OPEEATIONS. 



237 



GEOUND OPERATIONS. 



DRAINAGE IN PRACTICE. 



HAVING- considered the main principles on which 

 drainage rests and should be conducted, this 

 chapter will be devoted to the explanation and illus- 

 tration of its practice. The chief points are the 

 direction, distance apart, depth, fall, sizes, materials, 

 outlets, tools for making, 

 actual cutting, and laying 

 of the drains. 



Direction or Line 

 of Drains. — This is a 

 point that, above all others 

 in draining, needs the as- 

 sistance and advice of civil 

 engineers or experienced 

 drainers. Perhaps the 

 most common method is 

 that of running the drains 

 parallel with the line of 

 level or even fall of the 

 ground. This mostly an- 

 swers well where the soil 

 and subsoil are of equal 

 depths and uniform quality 

 throughout ; but in many 

 cases this mode of draining 

 is almost useless on ac- 

 count of the difficulty of 

 securing a fall. And be- 

 sides, as already observed, 

 a single or few drains so 

 placed as to intercept the 

 overflow water from higher 

 levels, will cut off lower 

 springs, and so dry at 

 times without more trouble 

 the ' whole of a field or 

 garden. 



There are other advan- 

 tages at times in draining 

 obliquely across the incUne of the land, such as the 

 more equal distribution and slower removal of the 

 water from the surface tilth. Bearing in mind what 

 has been said on the chemical, cultural, and mechani- 

 cal importance of water in motion through the land, 

 it will be obvious that it might prove far from ad- 

 vantageous to remove it too rapidly ; provided it 

 moves, most of the advantages of drainage will be 

 secured, and the slow motion may prove far better 

 than a rapid run. The popular idea, that the faster 

 water is discharged from the mouths of the drains 

 after a shower the better, may not by any means 

 prove correct. Drains that discharge muddy water 



Fig. 12.— A, witli the slope ; b, obliqviely across 

 drains at right angles witu fall. 



in their haste, may impoverish almost as much as 

 enrich the land. In the three illustrations here given, 

 that of draining with the slope, at right angles with it, 

 and obliquely across it, the latter will mostly be found 

 the best. ISome, however, prefer the line of the 

 slope as being at once the more simple and easy, and 

 there can be no question that the major portion of 

 common tile-draining in fields follows the line of 

 the surface soil or subsoU. 



Distance Apart of 

 Drains. — This is con- 

 siderably influenced by 

 their depth, as, unless in 

 the most tenacious clays, 

 the deeper the drains the 

 more land will they lay 

 dry on either side of them. 

 Hence the advocates of 

 very deep drains, such, for 

 example, as from four to 

 five feet, mostly couple 

 the extra depth with extra 

 distances apart. A yet 

 safer and more sure crite- 

 rion of proper distance 

 may generalLv be found in 

 the character of the soil; 

 the more tenacious the 

 latter, the closer in reason 

 the drains should be to 

 each other; the more 

 porous, the farther apart. 

 There are, however, ex- 

 ceptions to the latter rule, 

 for not unfrequently the 

 excessive moisture in por- 

 ous soils rises up from 

 below, and may need in- 

 terception and removal by 

 a system of closely- placed 

 drains. The extremes of 

 distances may generally 

 be found between twelve and thirty feet. The 

 latter may not prove too far apart on good porous 

 soil ; the former is seldom too close on stiff tenacious 

 clays. Fifteen, eighteen, twenty, and twenty-four 

 feet are popular distances. 



Of course these distances refer to the collecting 

 or feeding, and not the main drains. One or more of 

 the latter will generally be found sufficient for a 

 garden. They should be placed at the lowest point, 

 be larger and have a sharper fall than the others. 

 All the secondary drains should enter the mains at 

 easy angles or curves, as shown in Fig. 13. This 

 simple expedient is one of the surest means of pre- 



