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xxx Dunes. HOLLAND.
hus carried off. In these cases a system of dykes, one within the
other, and each provided with a canal on its exterior, forms an as-
cending series of levels, from the lower of which the water is grad-
ually transferred to the higher, and thence finally into the principal
channels. An excellent example of this is seen in the Schermer
Polder (p. 344), where four different levels have been formed. These
canals, although separate from one another, are all provided with
means of communication, by which if necessary the water from
the higher can be discharged into the lower.
The extraordinary fertility of the land thus reclaimed is chiefly
accounted for by the fact, that superfluous water can be removed
by means of the water-wheels on the shortest notice, while in dry
seasons a thorough system of irrigation is constantly available.
The appearance of these polders differs materially from that of
the rest of the country. The speculators by whom they are drained
map them out with mathematical precision into parcels, separated
by canals and rows of trees at right angles, and furnished with
houses of precisely uniform construction, all affording manifest
indications of the artificial nature of the ground. ‘The polders
often lie under water in winter, but this by no means impairs
the fertility of the soil, provided the water is not salt.
The principal polders are the Beemster, Purmer, Schermer
(pp. 342, 341), that of Haarlem (p. 258), reclaimed in 1840-53,
and the recently-drained polder of the Y (p. 337). Tt is now
proposed to convert the whole of the Zuider Zee into a polder,
whereby Holland would gain an additional province of 687 sq. M.
im area at an estimated cost of 120 million florins, or about 341.
sterling per acre.
Dunss, or downs, are the low sand-hills, 30-160 ft. in height,
which extend along the coast of Holland and Flanders, having
been thrown up by the action of the wind and waves. Those
nearest the sea are of very unsubstantial consistency, and being
frequently altered in shape by the wind they afford little or no sup-
port to vegetable life. Between the central downs (the highest and
broadest) and those farther inland , 1s situated an almost uninter-
rupted tract of pasture and arable land, studded with cottages, and
producing excellent potatoes. Most of the downs are honeycombed
with rabbit-warrens, which often afford excellent sport.
Tn order to prevent the sand of the downs from covering the
adjacent land, they are annually sown with the plants that most
readily take root in such poor soil, especially the reed-grass( Dutch,
helm; arundo arenarea). In course of time the roots spread and
entwine in every direction, thus gradually consolidating the sand.
A substratum of vegetable soil once formed, the arid and useless
sand-hill is converted into a smiling and fertile agricultural district,
in which even plantations of pines appear to thrive. |