Book III. 



DRAINING QUARRIES. 



637 



cient to afford the watera ready fall into the furrows, which should likewise 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 office of drains, the water coming upon the ridges being thus 

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

 rising of the ground or other causes ; 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 tlian 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 drain- 

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

 tise on Draining. 



Sect. V. Methods of draining Mines y Quarries, and Pits. 

 3955. Where pits, mines, or quarries, happen to be formed at the bottom of declivities, 

 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- 497 a). 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 qr 

 pit is formed, that may conduct the water it possesses to the porous body that is below it ; 

 as, where such a stratum is discovered by cutting into it, much of the water may be 

 drawn off and prevented from passing down. But notwithstanding the water from above 

 may he cut off in this way, a quantity sufficient to inconvenience the working of the 

 mine or pit may still filtrate from the sides of the porous bed, even though it may in- 

 cline in the direction of the lower ground. When this is the case, it may, however, 

 be readily taken away at some place in it. To accomplish this, and thereby obviate the 

 effects of the water, the termination of the porous stratum (fg. 497 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 admit the water to flow off with more expedition. Where, 

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

 the termination of the porous material, the drain need only be cut a little way into that, 

 as by boring through the rest a sufficient passage may I)e given to discharge the water. 

 In this way, the draining of such grounds as lie above or near to mines or pits may be 

 of great advantage. 



3956. Where a quarry or other pit to be dried (Jig. 498 a) is situated above a porous 

 sfraiwm, whether 



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of rock or gravel 

 it may some- 

 times be drained 

 by boring into 

 the latter (6). 

 In this way dif- 

 ferent chalk pits 

 and lime quar- 

 ries have been 



