136 



THE FARMERS' MONTHLY VISITOR. 



Frniii III^' Phituiicliitiia Fannti's Ciibiiiet. 



Elements of Practictil Agriculture. 



DRAINING. • 



Princi|)les to be ever kept in mind by tlic tillage farmev are to keep his land 

 dry rich and clean. The first in order of these principles, and an essential 

 one' to be recrarded in cold and humid countries, is to keep t)ie land dry. 



While a certain portion of water is essential to vegetation, an excess oj it 

 may prove greatly injurious. In the colder countries an e.xccss of water is 

 one of the main causes of infertility, and a primary purpi 

 man there is to carry it away from the ground. . , c •, 



The water whicii falls from the atmospliere dees not sink to an indehnite 

 depth, nor o-enerally tn a great depth, in tlie earth. It is either retained at or 

 near the surface where it falls, and whence it is evaporated, or it finds its way 

 to a lower level, by channels upon the surface, or in chinks of rocks, or beds 

 of gravel, sand, and otrier permeable substances beneath the surface. 



When water staonates at or near the surface, or when, having penetrated 



"S5^;>i;i.^ 



%\ IjavT-; 



iiose of the hu.sbaiid- 



to pervious substances below the surface, it is finding its way to u lower lev- 

 el the purpose of the drainer is to confine it to a determinate cliannel, and 

 carry it away by some convenient outlet, in order that- it may not overfiow or 



Eitiirit-G lllC soil' 



The drains for conveying away water from the surface are :— The ditches 

 of fields, v.'hich ought to be so laid out as to favor tlie descent of water, the 

 open furrows whicli are formed by the ridges, and trenches dug in the places 

 necessary for allowing a passage to the water. „ , ^ , 



Th- trenches for carrying away surface water, are usually left uncovered, 

 and they are termed open drains. But sometimes they are partly filled with 

 Btones or other substances, and then covered v^ith earth, so that while tlie 

 Burface water may sink down and be carried away, the tilling instruments 

 may not be interrupted.? 



In the forming of open drains, the dimensions must be fixed with relation 

 to the quantity of water to be carried away, and the direction determined by 

 the natural flow of the water, or by the particular course by which it is ex- 

 pedient to conduct it from the ground. In general, open drains are formed 

 in the hollows or lower parts of the land to be drained, so tliat the water may 

 find access to tliera from the higher gTounds, or sometimes they are formed a- 

 cross the line of descent, in order to intercept the water which runs from the 

 higher grounds to the lower. 



In open drains, of whatever depth, the sides should possess a declivity from 

 the top to the bottom, to prevent tliein from crumbling down and being under- 

 mined by the current. Except in the case of rock, this inclination should 

 not be less than 45 degrees; and, when the eartli is soft, and tlie flow of wa- 

 ter considerable, it should exceed 45 degrees. In all cases, the earth should 

 be spread from the edge of tiie trench backwards, so that the water from tlie 

 land on each side rnay have access to it. 



When drains of tliis class are covered, they are generally made from 2 1-3 

 to 3 feet deep, and filled with stones or otiier loose materials to within a foot 

 of tlie surface. They are usually in this case carried through the hollow pla- 

 ces, where the water of the land stagnates, or tends to How. 



The further end to be eft'ected by draining is to form ciiannels of water 

 which has already sunk into the ground, and is cither retained by it, or is 

 finding its way beneath the surface from a higher to a lower level. It is the 

 intercepting of water below the surface that constitutes tlie most difiicultpart 

 of draining, and which requires the application of principles which it is not 

 necessary to apply in tlie case of siirface draining. 



t When tlie soil rests upon a retentive subsoil, the latter may present a 

 Burface of resistance to the water; or tlie water may have sunk down into tlie 

 subsoil, and be finding its way through the channels beneath. 



The substances through which the water finds its way with facility are the 

 looser earths, sands and gravels, the crevices of rocks, and beds of loose or 

 decomposing stones ; the substances which resist its progress are clays and 

 the harder rocks. 



If we shall penetrate a very little way into the looser portion of the earth, 

 we shall generally find a series of strata, consisting of gravel, sand, or clay 

 of different degrees of density. These strata are frequently horizontal, fre- 

 quently they follow nearly Ihe inclination of the surface, and frequently they 

 are broken and irregular. Sometimes the stratum is very thin, as a few inch- 

 es in thickness, and sometimes it is several feet thick; and sometimes the 

 traces of stratification disappear, and we find only, to a great depth, a large 

 mass of clay, or other homegeneous substances. 



When these substances are of a clayey nature, water finds its way through 

 them witli difficulty; when they are of a looser texture, water percolates 

 througli them freely. These last accordingly form natural conduits or chan- 

 nels for the water whicli is below the surface, when finding its waj' from a 

 higher to a lower level. 



When any bed or stratum of tliis kind, in which water is percolating, crops 

 out to the surface, the water which it contains will flow out and form a burst 

 or spring, oozing over and saturating the ground, as in the following figure, 

 which represents a section of the ground, from C to D. 



[Fig 30] 



Bv cutting a drain at A Fig. 99, the water of the stratum of sand C E, is 

 cut offbefnre it reaches the surface at C, where it forms the swamp C U. 



In like manner, in Fig. 30, by forming a drain at C or F, the water is cut 

 ofl-inits channel A B, and thus in relieving tire pressure from the higher 

 source, by giving egress to the water through the drain, the cause of the wet- 

 ness from E to U is removed. ^ ,, ■ u„u 



In lookino-at the sloping surface of any tract of ground, as a field, in wh ch 

 there is an Sozing or bursting of water, we shall generally distinguish the . 

 line wliere tlie wetness begins to appear on the surface, extending over a con- 

 siderable space, xxxxx, Fig. 31, the effects appearing in the wetness ol the 

 ground farther down the slope, as ,j,j,j. The line where the wetness begins, 

 and which 

 soil, the tende 



ncss, marks fo. in ...u-^v , j — ; ,. ,. /-. » a i <• „™ 



sh.mld follow. By cutting a drain nearly in this line as irom G to A, and tiom 

 L to A sutHciently deep to reach the porous stratum in which the water per- 

 colates' we shall intercept it before it readies the surface, and by carrying it 

 away in some other convenient outlet, A B. remove the cause of wetness. 



ther down the slope, as yipj. The line where the wetness begins, 



is o-enerally rendered perceptible by the change of color ot the 



ndency to produce subaquotie plants, and other indications of wet- 



s for the most part nearly the course which the line of the dram 



[Fig. 31.] 



This, accordingly forms, in the greater number of cases, he rule adopted 

 ,n practice for the laving out of drains upon the surface. The line is drawn 

 nearly at or a little above, the line of wetness, or, to use the common expres- 

 sion, between the wet and the dry. „ ^ 



Should the line of drain be drawn too much below the line of wetness as 

 at G Fig 20 then the trench would fail to intercept the water ; and further, 

 if it 'were filled with earth, stones, and other substances, in the way to be af- 

 terwards described, the whole, or a part, of the water would pass over it, and 

 the injury be unremoved. , ^ . ti .u 



Ao-ain, should the line be too much above the line of wetness, as at H,the 

 drain would fail to reach the channel of the water, and so would be useless. 



It is for this reason that, in common practice, the rule is, to draw the line 

 of the drain nearly between the wet and the dry, or a little above it, taking 

 care to give it the necessary descent, and to form it of sufficient depth to 

 reach the pervious bed or stratum in which the water is contained. 



But as water may arrive at the surface in diffi-rent ways, and the wetness 

 be produced by difierent causes, so variations from this rule of lining out the 

 drain may be required, and the judgment of the drainer is to be shown in a- 

 dapting the course of his drain to the change of circumstances. 



Sometimes in a hollow piece of ground, feeders may reach the descent, as 

 in Fio-. 32; and ihe water may be forced upwards by the pressure from each 

 side of the hollow, and thus form the swamp from A to B. It may not be 

 necessary here to cut a trench on each side along the line of wetness at A 

 and B ; a single trench C, cut in the hollow, and giving egress to the water, 

 may relieve the pressure and remove the swamp. 



(Fig. 32.] 



Sometimes upon a sloping surface, one pervious stratum, in which water 

 percolates, mav produce more than one line of springs, as at B and A, in the 

 following figure. Here a single drain cut at B will remove the cause oljwet- 

 ness at botlTswamps, without the necessity of the drain at A. 



When water is in like manner percolating- through one of these pervious 

 strata, and meets any obstruction, as a rock or bed of clay at A. Fig. 2!>, it is 

 stopped in its progress, and, by the pi-essureof the water from a higher source, 

 it is forced upwards, and thus saturates -the superjacent soil, as from D to E, 

 forming springs, or a general oozing. 



In either of these cases, and they are the most frequent that occur in prac- 

 tice, the object of the drainer is to reach the water in its subterraneous chan- 

 nel before it shall arrive at the surface, and to carry it away in a drain. 



[Fig. 33.] 



