Book III. 



DRAINING BOGS. 



693 



intercepting the descent of the water or spring, and thereby totally removing the cause 

 of wetness. This may be done where the depth of the superficial strata, and conse- 

 quently of the spring, is not great ; by making horizontal drains (Jig. 624. a) of consi- 



derable length across the declivities of the hills, about where the low grounds of the 

 valleys begin to form, and connecting these with others (b) made for the purpose of con- 

 veying the water thus collected into the brooks or runlets (c) that may be near. Where 

 the spring has naturally formed itself an outlet, it may frequently only be necessary to 

 bore into it (e), or render it larger, and of more depth ; which, by affording the water a 

 more free and open passage, may evacuate and bring it off more quickly, or sink it to a 

 level so greatly below that of the surface of the soil, as to prevent it from flowing into 

 or over it. 



4228. IVhere the uppermost stratum is so extremely thick as not to be easily penetrated, 

 or where the springs, formed by the water passing from the higher grounds, may be con- 

 fined beneath the third or fourth strata of the materials that form the declivities of hills 

 or elevated grounds, and by this means lie too deep to be penetrated to by the cutting of 

 a ditch, or even by boring {Darwin's Phytologia, p. 263.) ; the common mode of cutting 

 a great number of drains to the depth of five, six, or more feet, across the wet morassy 

 grounds, and afterwards covering them in such a manner as that the water may suffer no 

 interruption in passing away through them, may be practised with advantage, as much 

 of the prejudicial excess of moisture may by this means be collected and carried away, 

 though not so completely as by fully cutting off" the spring. 



4229. As water is sometimes found upon thin layers of clay, which have underneath 

 them sand, stone, or other porous or fissured strata, to a considerable depth ; by per- 

 forating these thin layers of clay in different places, the water which flows along them 

 may frequently be let down into the open porous materials that lie below them, and the 

 surface land be thus completely drained. 



4230. Where morasses and other kinds of wetnesses are formed in such low places and 

 hollows as are considerably below the beds of the neighbouring rivers, they may, pro- 

 bably, in many instances, be effectually drained by arresting the water as it passes down 

 into them from the higher grounds, by means of deep drains cut into the sides of such 

 hills and rising grounds, and, after collecting it into them, conveying it away by pipes, 

 or other contrivances, at such high levels above the wet lands as may be necessary : or 

 where the water that produces the mischief can, by means of drains, cut in the wet 

 ground itself, be so collected as to be capable of being raised by means of machinery, it 

 may in that way be removed from the land. 



4231. The drainage of lands that lie below the level of the sea can only be effected by 

 the public, and by means of locks erected for the purpose of preventing the entrance of 

 the tides, and by windmills and other expensive kinds of machinery constructed for the 

 purpose of raising the stagnant water. 



4232. The superficial wetness of lands, which arises from the stiflT retentive nature of 

 the materials that constitute the soils and the particular circumstances of their situations, 

 is to be removed in most cases by means of hollow surface drains, judiciously formed, 

 either by the spade or plough, and filled up with suitable materials where the lands are 

 under the grass system ; and by these means and the proper construction of ridges and 

 furrows where they are in a state of arable cultivation. 



4233. Having thus explained the manner m which soils are rendered too wet for the 

 purposes of agriculture, and shown the principles on which the over-proportions of mois- 

 ture may, under different circumstances, be the most effectually removed, we shall pro- 

 ceed to the practical methods which are to be made use of in accomplishing the business 

 in each case. 



Sect. II. The Methods of Draining Boggy Land. 



4234. In the drainage of wet or boggy grounds, arising from springs of water beneath 

 them, a great variety of circumstances are necessary to be kept in view. Lands of this 



Yy 5 



