Book III. DRAINING BOGS. 697 



water is evacuated, make it rise to a greater height than the level of its natural outlet. 

 The effect of which must be, that the water forming the spring, having found by these 

 means a fresh and more easy passage, will quickly relinquish its former openings, and 

 thus be prevented from running over and injuring the ground that previously lay lower 

 down than it. 



4241. But in su-amps or bogs that are extensive and very ivet, other drains or cuts than 

 such as convey off the springs must be made ; as, notwithstanding the higher springs 

 which chiefly cause the wetness may be intercepted, there may be lower veins of sand, 

 gravel, or other porous materials, from which the water must likewise be drawn off. In 

 cases of this nature, where the land is to be divided into enclosures, the ditches may be 

 formed in such directions as to pass through and carry off collections of water of this 

 kind, as well as those that may be retained in the hollows and depressions on the surface 

 of the land. There are in many places very extensive tracts of ground that are rendered 

 wet, and become full of rushes and other coarse plants, from causes of such a nature as 

 cannot be obviated by the making of either open or covered drains, however numerous 

 they may be. Lands in this situation are frequently termed holms, and mostly lie on the 

 sides of such rivers and brooks as, from the frequency of their changing and altering their 

 courses between their opposite banks, leave depositions of sand, gravel, and other porous 

 materials, by which land is formed, that readily admits the water to filtrate and pass 

 through it to the level of the last-formed channels, and which preserves it constantly in 

 such a state of moisture and wetness, as to render it productive of nothing but rushes and 

 other aquatic plants ; and if a pit or ditch be made in lands under these circumstances, 

 it quickly fills with water to the same level as that in the watercourse. This effect is, 

 however, more liable to be produced, as well as more complete, where the current of the 

 water is slow, and its surface nearly equal with that of the land, than where its descent 

 is rapid. Under such circumstances, while the river or brook remains at the ordinary 

 height, no advantage can be gained, whatever number of drains be formed, or in what- 

 ever direction they may be made. The chief or only means of removing the wetness of 

 land proceeding from this cause is, that of enlarging and sinking the bed of the stream, 

 where it can be effected at a reasonable expense : where there is only one stream, and it 

 is very winding or serpentine in its course, much may however be effected by cutting 

 through the different points of land, and rendering the course more straight, and thereby 

 less liable to obstruct the passage of the water. But in cases where there are more than 

 one, that should always be made the channel of conveyance for draining the neighbour, 

 ing land, which is the' lowest in respect to situation, and the most open and straight in its 

 course. It may likewise, in particular instances, be advantageous to stop up and divert 

 the waters of the others into such main channels, as by such means alone they may often 

 be rendered deeper, and more free from obstruction : the materials removed from them 

 may serve to embank and raise up the sides to a greater height, as while the water can 

 rise higher than the outlets of the drains, and flow backwards into them, it must render 

 the land as wet as it was before they were formed, and the expense of cutting them to 

 be thrown awav. 



4242. The collected rain-water, becoming stagnant on a retentive body of clay, or some 

 other impervious material, as it can have no outlet of the natural kind, causes such lands 

 to become soft and spongy, thus forming bogs of a very confined kind. As such bogs 

 are often situated verv trroatly below the ground that surrounds them, the opening of a 

 main drain, or conductor, to convey off the water collected by smaller drains, would be 

 attended, in manv instances, with an expense greater than could be compensated by the 

 land after it had been drained. The thickness of the impervious stratum that retains and 

 keeps up the water in such cases is often so great, that though the stratum below be of a 

 porous and open nature, such as sand, rock, or gravel, the water cannot of itself penetrate 

 or find a passage from the one into the other ; consequently, by its continued stagnation 

 above, all the different coarse vegetable productions that have for a great length of time 

 been produced on its surface, and probably the upper part of the soil itself, are formed 

 into a mass or body of peat earth, equal in softness to that of any bog originating from 

 water confined below, and less productive, and which is only capable of sustaining the 

 weight of cattle in verv dry seasons, when the wind and sun have exhaled and dried up a 

 great part of its surface moisture ; but even then it is incapable of admitting the plough 

 upon it. 



»d 3 «ion of which must W related by the extent of the bog They shoul Mj .cut «rougo «. 

 peat, or moist spongv upper soil, to the surface of the clay, or other reten £»e strat ir m . .atu a^, n c 

 11ms then be perforated or bored through in order to let the water ^^^SXeuS»S 

 by which it maybe absorbed and taken up. The same effect ^ighr be produ ^ ^^ conI1 4. 

 Web, or pit, in the middle or lowest part of the *^#"OTfflta5 the drains would 

 ing the other drains with it, as by such amethod ihe trouble and expen.e 01 uui.i 6 



