630 



PRACTICE OF AGRICULTURE. 



Part III. 



necessity of being formed at different distances, to the very bottom of the declivity : 

 these being afterwards in a great measure filled with loose stones, merely conveyed away 

 portions of surface water, without touching the spring, the great or principal cause of 

 the wetness. The effects of drains formed in this manner he asserts to be, that of ren- 

 dering the surface of the land in some degree drier, so long as they continue to run with 

 freedom ; but as they are liable soon to be obstructed and filled up by sand or other 

 materials, the water is often forced out in different places and directions, and thus 

 renders the land equally wet, if not more so, than it was before. In addition to this, it 

 is a more diflScult task to drain the ground a second time in a, proper method, from the 

 natural appearance of the ground being so much changed, and the bursts of the old 

 drains, as well as the greater difficulty of ascertaining the real situation of the springs. 



3932. It may sometimes happen, however, that where the highest are the strongest 

 outlets, they may be the main or leading sprijigs ; those which show themselves lower 

 down in the land being merely formed by the water of the main spring overflowing, and 

 finding itself a passage from an opening, or the porous nature of the materials of the soil 

 near to the surface, and from being obstructed somewhat further down in the ground by 

 some impervious stratum. This circumstance must, therefore, it is observed, be fully 

 ascertained before the lines for the ditches or drains are marked out. 



3 933. In cases where the banks or rising grounds are formed in an irregular manner {fig- 

 486.), and from the nature of the situ- 486 



ation, or the force of the vvater under- 

 neath, springs abound round the bases 

 of the protuberances, the ditches 

 made for the purpose of draining 

 should always be carried up to a 

 much higher level in the side of the 

 elevated ground than that in which the 

 water or wetness appears ; as far even 

 as to the firm unchanged land. By 

 this means the water of the spring 

 may be cut oflT, and the ground com- 

 pletely drained; which would not 

 be the case if the trench or drain 

 were formed on the line of the loose 

 materials lower down where the wa- 

 ter oozes out, which is liable to mis- 

 lead the operator in forming the 

 conducting trench, or that which is 

 to convey the water from the cross-drain on the level of the spring to the outlet or 

 opening by which it is discharged. But where the main or principal spring comes out 

 of a perpendicular or very steep bank, at a great height above the level of the outlet into 

 which it may discharge itself by means of a drain ; it will neither be necessary nor of any 

 utility to form a deep trench, or make a covered drain, all the way from such outlet up to 

 it ; as from the steepness of the descent the water would be liable, when the drain was thus 

 cut, from the thin strata of sand', and other loose materials, always found in such cases, to 

 insinuate itself under the bricks, stones, or other substances of which the drain was 

 formed ; to undermine and force them up by the strength of the current, or, probably, 

 in some instances, block the drain up by the loose sand or other matters, which may be 

 forced away and carried down by it. In situations of this kind, Johnston observes, it is 

 always the best way to begin just so far down the bank or declivity as, by cutting in a 

 level, the drain may be six or seven feet below the level of the spring; or of such a depth 

 as may be requisite to bring down the water to a level suitable to convey it away with- 

 out its rising to the surface, and injuring the lands around it. The rest of the drain, 

 whether it be made in a straight or oblique direction, need not be deep, and may, in 

 many instances, be left quite open ; it should, however, be carefully secured from the 

 treading of cattle, and, where the land is under an arable system of cultivation, also 

 from the plough. Where it is covered, the depth of about two feet may be sufficient. 

 There will not, in such drains, be any necessity fo the use of the auger in any part of 

 them. 



3934. Where there is a difficulty in ascertaining the line of the spring, and conse- 

 quently that of the cross drain, either from its not showing itself on the surface, or from 

 there not being any apparent outlet, it may, generally, be met with in carrying up the 

 conducting drain for conveying away the water : as soon as the operator discovers the spring, 

 he need not proceed any further, but form the cross drain on the level thus discovered 

 to such a distance on each side of the tail, or terminating part cf the strata, of whatever sort, 

 that contains the water, as the nature of the land, in regard to situation or other circum- 

 stances, may demand. Where, in forming a cross-drain, the line indicated by the spirit or 



