DRAINAGE. 



run. One foot is sufficient fall for a ' with the surface. To save the ex- 



drain 300 feet in length, provided the 

 drains be not more than twenty feet 

 apart. The main drains, by being 

 laid obliquely across the fall of the 

 ground, will help to take off a part of 

 the surface water. It is evident that 

 the drains can seldom be in a straight 

 line unless the ground be perfectly 



pense of stone or tiles, drains are 

 frequently made si.v inches wide at 

 the bottom ; a narrow channel is cut 

 in the solid clay, two or three inches 

 wide and six deep (a), leaving a shoul- 

 der on each side to support a sod, 

 which is cut so as to fit the drain, and 

 rest on the shoulders {h) ; this sod 



even. They should, however, never keeps the earth from filling the chan- 



have sudden turns, but be bent grad- 

 ually where the direction is changed. 

 The flatter the surface and the stiffer 

 the soil, the greater number of drains 

 will be required. It is a common 

 practice with drainers to run a main 

 drain directly down the slope, how- 

 ever rapid, and to carry smaller 

 drains into this alternately on the 

 right and left, which they call her- 

 ring-bone fashion. But this can only 

 be approved of where the ground is 

 nearly level, and where there is very 

 little fall for the main drain. A con- 

 siderable fall is to be avoided as much 

 as possible ; and every drain should 

 lie obliquely to the natural run of the 

 water. It generally happens that, 

 besides surface water, there are also 

 some land-springs arising from a va- 

 riation in the soil ; these should be 



nel (see Fig. 4). 



It is filled up as de- 



scribed before : such drains are made 

 at a small expense, and will last for 

 many years. 



" Where the clay is not sufficiently 

 tenacious, the bottom of the drain is 

 sometimes cut with a sharp angle, 

 and a twisted rope of straw is thrust 

 This keeps the earth from 



into It 

 carefully ascertained, and the drains ' falUng in, and the running of the wa- 

 should be so laid as to cut them off. | ter keeps the channel open ; the straw, 

 " In draining clay land, where there | not being exposed to the air, remains 

 is only a layer of a few inches of 

 looser soil over a solid clay, which 

 the plough never stirs, the drains 

 need not be deeper than two feet in 



the solid clay, nor wider than they 

 can be made without the sides falling 

 in. The common draining tile, which 

 is a flat tile bent in the form of half 

 a cyUnder, and which can be made at 

 a very cheap rate, is the best for ex- 

 tensive surface draining. In solid 

 clay it requires no flat tile under it ; 

 it is merely an arch to carry the loose 

 stones or earth with which the drain 

 is filled up. Loose round stones or 

 pebbles are the best where they can 

 be procured ; and in default of them, 

 bushes, heath, or straw may be laid. 

 In grass land the sod may be laid 

 over the drain, after it has been filled 

 up, so as to form a slight ridge over 

 it. This will soon sink to a level 



a long time without decaying. It is 

 a common mistake to suppose that 

 in these drains water enters from 

 above ; it rises from below. 



" The best materials for large main 

 drains, where they can be procured, 

 are flat stones which readily split, and 

 of which a square or triangular chan- 

 nel is formed in the bottom of the 

 drain. If the drain is made merely 

 as a trunk to carry off the water, it 

 is best to fill it up with earth, well 

 pressed in, over the channel made by 

 the stones. A very useful draining 

 tile is used in Berkshire and other 

 places, which requires no flat tile un- 

 der it, even in loose soils, because it 

 has a flat foot to rest on, formed of 

 the two thick edges of the tile, which, 

 nearly meeting when the tile is bent 

 round, form the foot. The section of 

 the tile is like a horseshoe. It is 



237 



