342 
CONSTRUCTION OF DIKES. 
the current, are employed to facilitate the deposit of slime, 
before a regular enclosure is commenced. Usually, however, 
the first step is to build low and cheap embankments, extend¬ 
ing from an older dike, or from high ground, around the 
parcel of flat intended to be secured. These are called summer 
dikes ( sommer-deich , pi. sommer-deiche , German ; zomerkaai , 
zomerkade , pi. zoruerJcaaie, zomerhaden , Dutch). They are 
erected wdien a sufficient extent of ground to repay the cost 
has been elevated enough to he covered with coarse vegetation 
fit for pasturage. They serve both to secure the ground from 
overflow by the ordinary flood tides of mild weather, and to 
retain the slime deposited by very high water, which would 
otherwise be partly carried off by the retreating ebb. The 
elevation of the soil goes on slowly after this ; but when it has 
at last been sufficiently enriched, and raised high enough to 
justify the necessary outlay, permanent dikes are constructed 
by which the water is excluded at all seasons. These embank¬ 
ments are constructed of sand from the coast dunes or from 
sandbanks, and of earth from the mainland or from flats out¬ 
side the dikes, bound and strengthened by fascines, and pro¬ 
vided with sluices, which are generally founded on piles and 
of very expensive construction, for drainage at low water. 
The outward slope of the sea dikes is gentle, experience having 
shown that this form is least exposed to injury both from the 
waves and from floating ice, and the most modern dikes are 
even more moderate in the inclination of the seaward scarp 
than the older ones.* The crown of the dike, however, for the 
last three or four feet of its height, is much steeper, being 
intended rather as a protection against the spray than against 
the waves, and the inner slope is always comparatively abrupt. 
The height and thickness of dikes varies according to the 
elevation of the ground they enclose, the rise of the tides, the 
direction of the prevailing winds, and other special causes of 
exposure, but it may be said that they are, in general, raised 
from fifteen to twenty feet above ordinary liigli-w T ater mark. 
* The inclination varies from one foot rise in four of base to one foot 
in fourteen.— Kohl, iii, p. 210. 
