DRAINAGE. 



main line of springs, it is best to pro- 

 ceed experimentally by making pits a 

 few feet deep, or by boring in various 

 parts wliere water appears, observing 

 the level at which the water stands 

 in these pits or bores, as well as the 

 nature of the soil taken out. Thus 

 it will generally be easy to ascertain 

 whence the water arises, and how it 

 may be let off. When there is a 

 mound of light soil over a more im- 

 pervious stratum, the springs will 

 break out all round the edge of the 

 mound ; a drain laid round the base 

 will take ofTall the water which arises 

 from this cause, and the lower part 

 of the land will be efTectually laid dry. 

 So, likewise, where there is a hollow 

 or depression of which the bottom is 

 clay, with sand in the upper part, a 

 drain laid along the edge of the hol- 

 low, and carried round it, will prevent 

 the water running down into it and 

 forming a marsh at the bottom. 



" When the drains cannot be carried 

 to a sufficient depth to take the water 

 out of the porous stratum saturated 

 with it, it is often useful to bore nu- 

 merous holes with a proper auger in 



the bottom of the drain through the 

 stifTer soil, and, according to the prin- 

 ciple explained in the diagram, the 

 water will either rise through these 

 bores into the drains and be carried 

 off, and the natural springs will be 

 dried up, or it will sink down through 

 them as at G, in the section, if it lies 

 above. This method is often advan- 

 tageous in the draining of peat bogs, 

 which generally lie on clay or stiff 

 loam, with a layer of gravel between 

 the loam and the peat, the whole ly- 

 ing in a basin or hollow, and often on 

 a declivity. The peat, though it re- 

 tains water, is not pervious, and 

 drains may be cut into it which will 

 hold water. When the drains are 

 four or five feet deep and the peat is 

 much deeper, holes are bored down 

 to the clay below, and the water is 

 pressed up through these holes, by 

 the weight of the whole body of peat, 

 into the drains, by which it is carried 

 off. The cuts, Figs. 2 and 3, repre- 

 sent a common case of this kind ; h, h 

 (3) are the sides of a hill ; the swampy 

 lot below is filled with springs, which 

 are, however, drained by running a 



Fig. 3. 



i*Sil^M, 



ditch (ft, ft) across it and sinking holes 

 into the subsoil. One of these holes 

 is shown in Fig. 2 (a, ft), and the man- 

 ner in which it conveys the surface 

 water away. The bottom of the 

 drains is sometimes choked with 

 loose sand, which flows up with the 

 w ater, and they require to be cleared 

 repeatedly : but this soon ceases after 

 the first rush is past, and the water 



rises slowly and regularly. The sur- 

 face of the peat being dried, dressed 

 with lime, and consolidated with 

 earth and gravel, soon becomes pro- 

 ductive. If the soil, whatever be its 

 nature, can be drained to a certain 

 depth, it is of no consequence what 

 water may be lodged below it. It is 

 only when it rises so as to stagnate 

 about the roots of plants that it is 



235 



