Book IIL DRAINING MINES, QUARRIES, LAKES, &c. 705 



sinking in through the clay, as in soils of a contrary kind. Where th-e happen to be 

 hollows or irregularities in the surface of the land, water may often be observed to con- 

 tinue standing in them, at a distance of but a few feet from the drain. In draining such 

 lands, it will always be necessary, in the first place, to make a large or conducting drain 

 at the lowest part, or the end of the field, for the purpose of receiving and conveying away 

 the water collected by the smaller collateral cuts which it may be necessary to make on 

 each side of it. Where it suits for the purpose of dividing the land, this principal drain 

 may be better open than covered, as by that means the mouths or outlets of the different 

 small drains that come into it may be conveniently examined, and cleared out when 

 necessary. 



4272. The construction of the ridges in such soils, so that they may accord with the 

 declivity, is a matter which must be carefully kept in view. They should in all such 

 cases have a degree of elevation or roundness in the middle, sufficient to afford the water 

 a ready fall into the furrows, which likewise should have such a depth and fall as may 

 take it quickly into the drains. The ridges, besides being well laid up, should have 

 small open drains formed in a slanting direction across them, in such a manner as to 

 form communications with one another, and with the furrows ; by which means they 

 are made to perform the oflSce of drains ; the water coming upon the ridges being thus 

 readily conveyed into the furrows, along which it proceeds till impeded in its course by 

 the rising of the ground or other cause ; it then passes through the open cross-drains into 

 others where the descent is greater, and is ultimately conveyed off into the ditch, or other 

 passage, at the bottom of the enclosure. The elevation of the ridges should probably, 

 too, be made greater for the winter than the summer crops, as there must be much more 

 injurious moisture at the former than the latter season. This may be easily accomplished 

 at the time of ploughing the land. Some useful observations on this description of 

 drainage will be found in Marshal's work on Landed Property, and in Dr. Anderson's 

 Treatise on Draining. - ->''^'^ ^'* .lOi:! 



Sect. VI. Methods of draining Mines, Quarries, Pits, Ponds, and Lakes. 



4273. Where pits, mines, or quarries, happen to be formed at the bottom of decliviiies, 

 and are inconvenienced or wholly obstructed, either in the digging or working, by the 

 water contained in them, it may be possible, in many cases, to prevent its coming into 

 such mines or pits, by cutting or boring into the lower parts of the porous strata 

 (Jig. 641. ). In order to accomplish this object, it will be necessary to ascertain if any 



porous stratum presents itself higher up the elevation than the place where the mine or 

 pit is formed, that may conduct the water it contains to the porous body below it ; as by 

 cutting into such stratum, where discovered, much of the water may be drawn off and 

 prevented from passing down. But notwithstanding the water from above may be cut 

 off in this way, a quantity suflRcient to inconvenience the working of the mine or pit 

 may still filtrate from the sides of the porous bed, even though it may incline in the 

 direction of the lower ground. When this is the case, it may, however, be readily taken 

 away at some place in the bed. To accomplish this, and thereby obviate the effects of 

 the water, the termination of the porous stratum {fig. 641. a) below the pit must be 

 ascertained ; and where there is any mark of a natural outlet at the place, a large drain 

 should be formed, in order to permit the water to flow off with more expedition. Where, 

 however, there is a thick bed of some impervious substance, such as clay, placed upon 



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