employed to keep the land dry enough for pasturage
and cultivation. [Footnote: The elevation of the
lands enclosed by dikes—or polders, as
they 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 cannot 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 occasional by drying
and consolidation. 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 Thans, p.
152]
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 thousand acres
wore reclaimed from the waters, and added to the agricultural
domain of the Netherlands, between 1815 and 1855.
The most important of these undertaking was the draining
of the Lake of Haarlem, and for this purpose some
of the most powerful hydraulic engines over constructed
were designed and executed. [Footnote: The principal
engine, of 500 horse-power, drove eleven pumps with
a total delivery of 31,000 cubic yards per hour.—Wild,
Die Netherland, i., p. 87.] The origin of this lake
is unknown. It is supposed by some geographers
to be a part of an ancient bed of the Rhine, the channel
of which, as there is good reason to believe, has
undergone great changes since the Roman invasion of
the Netherlands; by others it is thought to have once
formed an inland marine channel, separated from the
sea by a chain of low islands, which the sand washed
up by the tides has since connected with the mainland
and converted into a continuous line of coast.
The best authorities, however, find geological evidence
that the surface occupied by the lake was originally
a marshy tract containing within its limits little
solid ground, but many ponds and inlets, and much
floating as well as fixed fen.
In consequence of the cutting of turf for fuel, and
the destruction of the few trees and shrubs which
held the loose soil together with their roots, the
ponds are supposed to have gradually extended themselves,
until the action of the wind upon their enlarged surface
gave their waves sufficient force to overcome the
resistance of the feeble barriers which separated
them, and to unite them all into a single lake.
Popular tradition, it is true, ascribes the formation
