GEOGRAPHICAL EFFECTS OF DEAINING. 431 



and superficial strata of a river-basin, the original equilibrium is 

 disturbed, the waters of tbe heavens are no longer stored up in 

 the earth to be gradually given out again, but are hurried out of 

 man's domain with wasteful haste ; and while the inundations of 

 the river are sudden and disastrous, its current, when the drains 

 have run dry, is reduced to a rivulet, it ceases to supply the 

 power to drive the machinery for which it was once amply suf- 

 ficient, and scarcely even waters the herds that pasture upon its 

 margin. 



The water of subterranean currents and reservoirs, as well as 

 that of springs and common wells, is doubtless principally fur- 

 nished by infiltration, and hence its quantity must vary with 

 every change of natural surface which tends to accelerate or to 

 retard the drainage of the surface-soil. The drainage of marshes, 

 therefore, and all other methods of drying the superficial strata, 

 whether by open ditches or by underground tubes or drains, has 

 the same effect as clearing off the. forest in depriving the subter- 

 ranean waters of accessions which they would otherwise receive 

 by infiltration, and in proportion as the sphere of such operation 

 is extended, their influence will make itself felt in the diminished 

 supply of water in springs and wells.* 



Geographical and Meteorological Effects of Aqueducts^ 

 Reservoirs and Ca/nals. 



Many of the great processes of internal improvement, such as 

 aqueducts for the supply of great cities, railroad cuts and em- 



* Babinet condemns the general draining of marshes. " Draining," says he, 

 " has been much in vogue for some years, and it has been a special object to 

 dry and fertilize marshy grounds. I believe that excessive dryness is thus pro- 

 duced, and that other soils in the neighborhood are sterilized in proportion." — 

 Etudes et Lectures, iv., p. 118. 



" The extent of soil artificially dried by drainage is constantly increasing, 

 and the water received by the surface from precipitation flows off by new 

 channels, and is in general carried off more rapidly than before. Must not 

 this fact exercise an influence on the regime of springs whose basin of supply 

 thus undergoes a more or less complete transformation ? " — Bernhakd Cotta, 

 Preface to Paramelle, Quellenkunde, p. vii., viii. 



The effects of agricultural drainage are perceptible at great depths. It has 

 been observed in Cornwall that deep mines are more free from water in well- 

 drained districts than in those where drainage is not generally practiced. — 

 EsQUiROS, Revue des Deux Mondea, 15 Nov., 1863, p. 430. The frequency of 



