412 CHANGES PEODUCED BY MAIT. 



water, rapidly extended themselves by abrasion of their borders, 

 and finally enlarged to pools, lakes and gulfs, like the Lake of 

 Haarlem and the northern part of the Zuiderzee. The cutting of 

 the wood and the depasturing of the grasses upon the sand-dunes, 

 converted them from solid bulwarks against the ocean to loose 

 accumulations of dust, which every sea-breeze drove farther land- 

 ward, burying, perhaps, fertile soil and choking up watercourses 

 on one side, and exposing the coast to erosion by the sea upon 

 the other. 



Geographical Effect of Physical Improvements in the 

 Netherlands. 



The changes which human action has produced within twenty 

 centuries in the Netherlands and the neighboring provinces, are 

 certainly of no small geographical importance, considered simply 

 as a direct question of loss and gain of territory. They have also, 

 as we shall see hereafter, undoubtedly been attended with some 

 cKmatic consequences ; they have exercised a great influence on 

 the spontaneous animal and vegetable hf e of this region, and they 

 can not have failed to produce effects upon tidal and other oceanic 

 currents, the range of which may be very extensive. The force 

 of the tidal wave, the height to which it rises, the direction of its 

 currents, and, in fact, all the phenomena which characterize it, as 

 well as all the effects it produces, depend as much upon the con- 

 figuration of the coast it washes, and the depth of water and 

 form of bottom near the shore, as upon the attraction which oc- 

 casions it. Every one of the terrestrial conditions which affect 

 the character of tidal and other marine currents has been very 

 sensibly modified by the operations I have described, and on this 

 coast, at least, man has acted almost as powerfully on the physical 

 geography of the sea as on that of the land.* 



Ancient Hydraulic Worhs. 



The hydraulic works of the Netherlands and of the neighbor- 

 ing states are of such magnitude that — ^with the exception of the 

 dikes of the Mississippi — they quite throw into the shade all 



* See, on the influence of the artificial modification of the coast-line on tides 

 and other marine currents, Starinq, De Bodem van Nederland, i., p. 279. 



