634 



PRACTICE OF AGRICULTURE. 



Part III. 



the rock, and consequently be 

 extremely difficult to cut, on 

 account of the nature and dis- 

 position of the stone : when 

 the water passing out on the 

 line of the springs can be 

 found by the auger in the 

 main drain, at the point 

 where it joins it, it will, it is 

 observed, be the more completely cut off; but where this is not practicable, the depth of 

 the small cuts may reduce it to such a level as will prevent its flowing over and injuring 

 the surface of the land below it. 



3943. In such hills as are constituted of alternate strata of rock, sand, and clay, 

 the surface of the latter may frequently be wet and swamp, while that of the 

 former is dry, and capable of producing good crops of grass ; in all such cases, in order 

 to drain the land completely, as many cuts will be necessary as there may happen divi- 

 sions of wet and dry soil : the summit, or most elevated part of such hills, being mostly 

 formed of loose porous materials, through which the rain and other water descends, till 

 its passage becomes obstructed by some impervious bed or stratum, such as clay, when it 

 is forced up to the surface, and runs or oozes over the obstructing stratum ; and after 

 having overflowed, the upper clay surface is immediately absorbed and taken up by the 

 succeeding porous one, and, sinking into it in the same way as before, passes out again 

 at the lower side of it, and renders the surface of the next clayey bed prejudicially wet 

 as it had done in the first. In this way the same spring may affect all the other strata of 

 the same kind of which the hill consists, from the highest part down the whole of the 

 declivity, and produce in the bason, or hollow at the bottom, a lake or bog, should there 

 not happen to be a passage or opening to take away the waten In order effectually to 

 drain hills of this kind, it will be the most advisable to begin by forming a trench 

 along the upper side of the uppermost rushy soilf by which means the highest spring 

 may be cut off; but as the rain and other water that may come upon the next portion 

 of porous soil may sink down through it to the lowest part, and produce another 

 spring, a second cut must be made in that part to prevent the water from affecting the 

 surface of the succeeding clayey bed. And similar cuts must be formed so far down 

 the declivity as the same springs continue in the same way to injure the land, and in some 

 cases a sufficiency of water may probably be obtained to irrigate the land below, or some 

 other useful purpose. 



Sect. III. Of the Methods of draining Mixed Soils. 



3944. Where the soil is of a mixed and varied nature, but the most prevailing parts of 

 the clayey kind, the business of draining is considerably more tedious and difficult than 

 where the superficial and internal parts have greater regularity. In such sorts of lands, 

 as all the different collections of -water are perfectly distinct from each other, by means of 

 the beds of clay that separate them, eaih collection becomes so much increased, or ac- 

 cumulated, in the time of heavy rains, that they are filled quite to the level of the surface 

 of the day by which they are surrounded ; when the water getting a free passage, as it 

 would over the edges of a bowl or dish, overflows and saturates the surface of that bed of 

 clay in such a manner, as to render it so perfectly wet and sour, that its produce becomes 

 not only annually more and more scanty, but the soil itself more sterile and unpro- 

 ductive. 



3945. From the sand-beds (fg. 491 a, a, a) in such cases having no communication 

 with each other,'it must evidently require as many drains (b,b,b) as there are beds of this 

 kind, in order fully to draw off , . 

 the water from each of them. 

 A drain or trench is therefore vj^aflj^S^ 

 recommended to be cut from 

 the nearest and lowest part of --.^-...v.;,;.^....^;.-. ,- 

 the field intended to be drained W^-?^^^^^^iy^^^ 

 (c), up to the highest and most 

 distant sand-bank (cZ), in such a ^^4^'^ 



line of direction as, if possible, ^j^PV^i^^ ^r^r;;;--,::: ;- - .- ,^ ,-j^ ^fS.^.xsH%<s\ 



to pass through some of the -^'y " '^ ^^^^^^!^ ^4f^p^ '1^ '^amr^'iniWm 

 intermediate sand-beds, and 

 prevent the labor and expense of making longer vuts on the sides, which would otherwise 

 be requisite. 



3946. fVhere the different beds of sand and day are of less extent, and lie together with 

 greater regularity, they can be drained in a more easy manner with less cutting, and of 

 course at less expense. Below the layers or beds of sand and clay that lie, in this 

 manner, alternately together, and nearly parallel to each other, is generally a body 



491 



