720 



DRAINING. 



general origin of that wetness of land which it is the 

 object of under-draining to remove, will be found to 

 be the existence of water in substrata of sand, gravel, 

 open rock, or other porous substances, which either 

 lead to the surface, or, having no natural outlet, be- 

 come filled or saturated, while the pressure of more 

 water coming from a higher source, forces that which 

 is in tlie lower part of the stratum upwards through the 

 superior strata to the surface ; thus occasioning either 

 hursts and springs, or a general oozing through the 

 soil. The object in under-draining, therefore, is not 

 to rat <-h the surface-water, but that which flows 

 through their inferior strata ; and, for this purpose, 

 it is necessary to make a sufficient channel, either at 

 the lower parts of the porous stratum, or in such part 

 of it as may most conveniently carry off the water, 

 so as the pressure referred to may be relieved, or the 

 water intercepted before it reaches the surface. It 

 must always be kept in mind, then, tliat under-drain- 

 ing and surface-draining are operations essentially 

 distinct ; and every care must be used in practice 

 not to blend them in the execution. If surface-water 

 be allowed to get into covered drains, the sand and 

 mud which it will carry into these subterraneous 

 channels will soon choke them up, and occasion 

 bursts, creating, as may be conceived, new swamps ; 

 while the expense of taking up and relaying the 

 under drains will be very great, and the execution 

 imperfect, the sides being found never to stand a se- 

 cond time so well as when first formed. 



Wetness of land, so far as it respects agriculture, 

 and is an object of draining, may generally depend 

 on the two following causes : first, on the water 

 which is formed and collected on or in the hills or 

 higher grounds, filtrating and sliding down among 

 some of tin- different beds of porous materials that 

 lie immediately upon the impervious strata, forming 

 springs below and flowing over the surface, or stag- 

 nating underneath it ; and, secondly, on rain or other 

 water becoming stagnant on the surface, from the 

 retentive nature of the soil or surface materials, and 

 the particular nature of the situation of the ground. 

 The particular wetness which shows itself in different 

 situations, in the forms of bogs, swamps, and mo- 

 rasses, for the most part proceeds from the first of 

 these causes ; but that superficial wetness which 

 takes place hi the stiff, tenacious, clayey soils, with 

 little inclination of surface, generally originates from 

 the latter. The most certain and expeditious method 

 of draining, in such cases, is that of 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 hori- 

 zontal drains of considerable length across the decli- 

 vities of the hills, about where the low grounds of 

 the valleys begin to form, and connecting these with 

 others made for the purpose of conveying the water 

 thus collected into the brooks or runlets that may be 

 near. Where the spring has naturally formed it- 

 self an outlet, it may frequently only be necessary 

 to bore into it, 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. 



Where 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 confined 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 ; the common mode of cutting a great 



number of drains to the depth of five, six, or more 1 

 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 or carried away, though not so completely 

 as by fully cutting off the spring. 



Where morasses and other kinds of wetnesses are 

 formed in such low places and hollows as are consi- 

 derably below the beds of the neighbouring rivers, 

 they may, probably, in many instances, be effectu- 

 ally 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, convey- 

 ing it away by pipes, or other contrivances, at such 

 high levels above the wet lands as may be necessary. 

 The drainage of lands that lie below the level of the 

 sea can only be effected 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. 



Draining hilly lands is not in general attended with 

 great expense, as the drains need seldom be covered 

 or filled up, but in such places as may be sufficient 

 for passages for the animals to cross by ; and though, 

 where the depth of the trench does not come to the 

 water confined below, it may be necessary to perforate 

 lower, there need not be any fear that the holes will 

 fill up, even where the drain is left open ; as the im- 

 petuosity of the water itself will remove any sand or 

 mud that may fall into $hem, where much flood or 

 surface water does not get hi. Small openings may, 

 however, be made along the upper side of the trench, 

 in order the more effectually to secure them against 

 any obstructions ; and in these the perforations may 

 be made, leaving the mouth of the holes about six 

 inches higher than the bottom of the drain, which 

 will be without the reach of the water that may be 

 collected during the time of heavy rains. 



One of the greatest improvements of the hilly sheep 

 pastures of Holland has been effected by drainage, 

 while the expense is comparatively small . The depth 

 and width of the small ones are only those of the 

 spade. They are usually carried across the face of 

 the hills in a slightly inclined direction, so as to avoid 

 the injury of too rapid a descent after heavy rains ; 

 and these small cuts open into a few larger, formed 

 with due regard to the same principle ; the whole at 

 last, for an extent of several hundred acres, being- 

 led into one still larger, which discharges itself .into 

 the nearest rivulet. Improvements or this kind are, 

 perhaps, of greater benefit to the individual proprie- 

 tors of land who undertake them than any other. 



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 lands, as the 

 collections of water are completely separated by the 

 intervening beds of clay, each becomes so much in- 

 creased in the time of heavy rains, as to rise to the 

 level of the surrounding surface ; when the water, 

 finding a free passage, as it would over the edges of 

 a bowl, overflows and saturates the surface of tliat 

 bed of clay, rendering it so wet and sour that its pro- 

 duce becomes annually more scanty, and the soil 

 itself more sterile and unproductive. From the sand- 

 beds in such cases having no communication with 

 each other, it must evidently require as many drains 

 as there are beds of this kind, in order fully to draw 

 off the water from each of them. 



The estate of Spottiswoode in Berwickshire af- 



