DKAINAGE BY BORHSTG. 425 



not absolutely necessary, at least profitable, exist in Great Britain, 

 and it is, therefore, very natural that the wealthy and intelhgent 

 farmers of England should have carried this practice farther, and 

 reaped a more abundant pecuniary return from it, than those of 

 any other country. 



Besides superficial and subsoil drains, there is another method 

 of disposing of superfluous surface-water, which, however, can 

 rarely be practiced, because the necessary conditions for its em- 

 ployment are not of frequent occmTence. Whenever a tenacious 

 water-holding stratum rests on a loose, gravelly bed, so situated 

 as to admit of a free discharge of water from or through it by 

 means of the outcropping of the bed at a lower level, or of deep- 

 lying conduits leading to distant points of discharge, superficial 

 waters may be carried off by oj)ening a passage for them through 

 the impervious into the permeable stratum. Thus, according to 

 Bischof, as early as the time of King Rene, in the first half of 

 the fifteenth century, when subsoil drainage was scarcely known, 

 the plain of Paluns, near Marseilles, was laid dry by boring, and 

 "Wittwer informs us that di-ainage is effected at Munich by con- 

 ducting the superfluous water into large excavations, from which 

 it filters through into a lower stratum of pebble and gravel lying 

 a httle above the level of the river Isar.* So at TV ashin^ton, in 

 the western part of the city, which lies high above the rivers Po- 

 tomac and Kock Creek, many houses are provided with dry wells 

 for draining their cellars and foundations. These extend through 

 hard, tenacious earth to the depth of thirty or forty feet, when 



* PliysiTialische Oeographie, p. 288. This method is now frequently em- 

 ployed in France. Details as to the processes will be found in Mangon^ 

 Pratique du Drainage, p. 78, et seq. Draining by driving down stakes, men- 

 tioned in a note in the chapter on the Woods, ante, is a process of the same 

 nature. 



In the United States, large tracts of marshy ground, and even shallow lakes 

 of considerable extent, have been sufficiently drained not only for pasturage 

 but for cultivation, without resort to any special measures for effecting that 

 end. The ordinary processes of rural improvement in the vicinity, such as 

 felling woods upon and around such grounds, and the construction of roads, 

 the side ditches of which act as drains, over or near them, aided now and then 

 by the removal of a fallen tree or other accidental obstruction in the beds of 

 small streams which flow from them, often suffice to reclaim miles square of 

 improductive swamp and water. See notes on p. 19, and on cedar swamps, 

 p, 204, ante. 



