404 DEAESTAGE OF LAIS^DS DIKED IIT. 



most of the land enclosed by dikes is still above low-water mark^ 

 and can, therefore, be wholly or partially freed from rain-water, 

 and from that received by infiltration from higher ground, by 

 sluices opened at the ebb of the tide. For this purpose the land 

 is carefully ditched, and advantage is taken of every favorable 

 occasion for discharging the water through the sluices. But the 

 ground can not be effectually di'ained by this means, unless it is 

 elevated four or five feet, at least, above the level of the ebb-tide, 

 because the ditches would not otherwise have a sufficient descent 

 to carry the water off in the short interval between ebb and flow, 

 and because the moisture of the saturated subsoil is always rising 

 by capillary attraction. Whenever, therefore, the soil has sunk 

 below the level I have mentioned, and in cases where its surface 

 has never been raised above it, pumps, worked by wind or some 

 other mechanical power, must be very frequently employed to 

 keep the land dry enough for pasturage and cultivation.* 



Dradnmg of the Lake of Saarlem. 



The substitution of steam-engines for the feeble and uncertain 

 action of windmills, in driving pumps, has much facilitated the 

 removal of water from the polders as well as the draining of 

 lakes, marshes and shallow bays, and thus given such an impulse 

 to these enterprises, that not less than one hundred and ten thou- 

 sand acres were reclaimed from the waters, and added to the 



briefly refers to the subject in De Bodem van Nederland, i., p. 356 et seq., 

 does not consider the evidence sufficient to prove anything more than the sink- 

 ing of the surface of the polders from drying and consolidation. — See Elisee 

 Recltts, La Terre, vol. i., pp. 730, 732. 



* The elevation of the lands enclosed by dikes — or polders, as such lands are 

 called in Holland — above low-water mark, depends upon the height of the 

 tides, or, in other words, upon the difference between ebb and flood. The 

 tide can not deposit earth higher than it flows, and after the ground is once 

 enclosed, the decay of the vegetables grown upon it and the addition of 

 manures do not compensate the depression occasioned by drying and consoli- 

 dation. On the coast of Zeeland and the islands of South Holland, the tides, 

 and of course the surface of the lands deposited by them, are so high that the 

 polders can be drained by ditching and sluices ; but at other points, as in the 

 enclosed grounds of North Holland on the Zuiderzee, where the tide rises but 

 three feet or even less, pumping is necessary from the beginning. — Staring, 

 Voormaals en TJiana, p. 153. 



