In an interesting report on the "Waterstaat" of the Netherlands,
presented to the British Government, we read: "To appreciate the beauty
of the Dutch science of hydrodynamics, it is necessary to understand
that, from first to last, it is a question of comparative levels. The
error of a centimètre in level might drown a province, or frustrate the
purpose for which some canal had been designed. Thus it may be said,
without exaggeration, that the most important institution in the kingdom
of the Netherlands is a certain antiquated pile at Amsterdam--but one of
many million pine-trees brought from Norway, on which the city is
perched,--which indicates the rise and fall of the outer waters of the
Zuyder Zee and German Ocean. For 200 years this pile has been watched
with anxiety by the burghers of the Netherlands, and a graduated scale
has been marked upon it, in which the mean water level is represented by
zero. It is known as the 'Amsterdamsche Peil,' and every hydraulic
undertaking in the country is measured by its standard, as having a
level of so many mètres or centimètres above or below the usual level of
the sea. The initials A. P. (Amsterdamsche Peil), O. A. (Zero of
Amsterdam), or Z. P. (Zero of Pile), are the forms of abbreviation most
generally used to represent the starting-point in all hydraulic
calculations; and one of these, with the signs + and -, must therefore
necessarily occur in every intelligible description of Dutch public
works."
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