Drainage.—It has been shown that the western provinces of Holland may be broadly defined as lying below sea-level. In fact the surface of the sea-clay in these provinces is from 11½ to 16½ ft. below the Amsterdam zero. The ground-water is, therefore, relatively very high and the capacity of the soil for further absorption proportionately low. To increase the reservoir capacity of the polder, as well as to conduct the water to the windmills or engines, it is intersected by a network of ditches cut at right angles to each other, the amount of ditching required being usually one-twelfth of the area to be drained. In modern times pumping engines have replaced windmills, and the typical old Dutch landscape with its countless hooded heads and swinging arms has been greatly transformed by the advent of the chimney stacks of the pumping-stations. The power of the pumping-engines is taken on the basis of 12 h.p. per 1000 hectares for every metre that the water has to be raised, or stated in another form, the engines must be capable of raising nearly 9 ℔ of water through 1 yd. per acre per minute. The main ditches, or canals, afterwards also serve as a means of navigation. The level at which it is desired to keep the water in these ditches constitutes the unit of water measurement for the polder, and is called the polder’s zomer peil (Z.P.) or summer water-level. In pasture-polders (koepolders) Z.P. is 1 to 1½ ft. below the level of the polder, and in agricultural polders 2½ to 3½ ft. below. Owing to the shrinkage of the soil in reclaimed lands, however, that is, lands which have been drained after fen or other reclamation, the sides of the polder are often higher than the middle, and it is necessary by means of small dams or sluices to make separate water-tight compartments (afpolderingen), each having its own unit of measurement. Some polders also have a winter peil as a precaution against the increased fall of water in that season. The summer water-level of the pasture polders south of the former Y is about 4 to 8 ft. below the Amsterdam zero, but in the Noorderkwartier to the north, it reaches 10½ ft. below A. P. in the Beschotel polder, and in reclaimed lands (droogmakerijen) may be still lower, thus in the Reeuwyk polder north of Gouda it is 21¼ ft. below.

The drainage of the country is effected by natural or artificial means, according to the slope of the ground. Nearly all the polders of Zeeland and South Holland are able to discharge naturally into the sea at average low water, self-regulating sluices being used. But in North Holland and Utrecht on the contrary the polder water has generally to be raised. In some deep polders and drained lands where the water cannot be brought to the required height at once, windmills are found at two or even three different levels. The final removal of polder water, however, is only truly effected upon its discharge into the “outer waters” of the country, that is, the sea itself or the large rivers freely communicating with it; and this happens with but a small proportion of Dutch polders, such as those of Zeeland, the Holland Ysel and the Noorderkwartier.

As the system of impoldering extended, the small sluggish rivers were gradually cut off by dikes from the marshy lands through which they flowed, and by sluices from the waters with which they communicated. Their level ranges from about 1½ to 4 ft. above that of the pasture polders. In addition, various kinds of canals and endiked or embanked lakes had come into existence, forming altogether a vast network of more or less stagnant waters. These waters are utilized as the temporary reservoirs of the superfluous polder water, each system of reservoirs being termed a boezem (bosom or basin), and all lands watering into the same boezem being considered as belonging to it. The largest boezem is that of Friesland, which embraces nearly the whole province. It sometimes happens that a polder is not in direct contact with the boezem to which it belongs, but first drains into an adjacent polder, from which the water is afterwards removed. In the same way, some boezems discharge first into others, which then discharge into the sea or rivers. This is usually the case where there is a great difference in height between the surface of the boezem and the outer waters, and may be illustrated by the Alblasserwaard and the Rotte boezems in the provinces of South and North Holland respectively. In time of drought the water in the canals and boezems is allowed to run back into the polders, and so serve a double purpose as water-reservoirs. Boezems, like polders, have a standard water-level which may hot be exceeded, and as in the polder this level may vary in the different parts of an extended boezem. The height of the boezem peil ranges between 11⁄3 ft. above to 15⁄6 ft. below the Amsterdam zero, though the average is about 1 to 12⁄3 ft. below. Some boezems, again, which are less easily controlled, have a “danger water-level” at which they refuse to receive any more water from the surrounding polders. The Schie or Delflands boezem of South Holland is of this kind, and such a boezem is termed besloten or “sequestered,” in contradistinction to a “free” boezem. A third kind of boezem is the reserve or berg-boezem, which in summer may be made dry and used for agriculture, while in winter it serves as a special reserve. The centuries of labour and self-sacrifice involved in the making of this complete and harmonious system of combined defence and reclamation are better imagined than described, and even at the present day the evidences of the struggle are far less apparent than real.

Geology.—Except in Limburg, where, in the neighbourhood of Maastricht, the upper layers of the chalk are exposed and followed by Oligocene and Miocene beds, the whole of Holland is covered by recent deposits of considerable thickness, beneath which deep borings have revealed the existence of Pliocene beds similar to the “Crags” of East Anglia. They are divided into the Diestien, corresponding in part with the English Coralline Crag, the Scaldisien and Poederlien corresponding with the Walton Crag, and the Amstelien corresponding with the Red Crag of Suffolk. In the south of Holland the total thickness of the Pliocene series is only about 200 ft., and they are covered by about 100 ft. of Quaternary deposits; but towards the north the beds sink down and at the same time increase considerably in thickness, so that at Utrecht a deep boring reached the top of the Pliocene at a depth of 513 ft. and at 1198 ft. it had not touched the bottom. At Amsterdam the top of the Pliocene lay 625 ft. below the surface, but the boring, 1098 ft. deep, did not reach the base of the uppermost division of the Pliocene, viz. the Amstelien. Eastward and westward of Amsterdam, as well as southward, the Pliocene beds rise slowly to the surface, and gradually decrease in thickness. They were laid down in a broad bay which covered the east of England and nearly the whole of the Netherlands, and was open to the North Sea. There is evidence that the sea gradually retreated northwards during the deposition of these beds, until at length the Rhine flowed over to England and entered the sea north of Cromer. The appearance of northern shells in the upper divisions of the Pliocene series indicates the approach of the Glacial period, and glacial drift containing Scandinavian boulders now covers much of the country east of the Zuider Zee. The more modern deposits of Holland consist of alluvium, wind-blown sands and peat.[3]

Climate.—Situated in the temperate zone between 50° and 53° N. the climate of Holland shows a difference in the lengths of day and night extending in the north to nine hours, and there is a correspondingly wide range of temperature; it also belongs to the region of variable winds. On an average of fifty years the mean annual temperature was 49.8° Fahr.; the maximum, 93.9° Fahr.; the minimum, -5.8° Fahr. The mean annual barometric height is 29.93 in.; the mean annual moisture, 81%; the mean annual rainfall, 27.99 in. The mean annual number of days with rain is 204, with snow 19, and with thunder-storms 18. The increased rainfall from July to December (the summer and autumn rains), and the increased evaporation in spring and summer (5.2 in. more than the rainfall), are of importance as regards “poldering” and draining operations. The prevalence of south-west winds during nine months of the year and of north-west during three (April-June) has a strong influence on the temperature and rainfall, tides, river mouths and outlets, and also, geologically, on dunes and sand drifts, and on fens and the accumulation of clay on the coast. The west winds of course increase the moisture, and moderate both the winter cold and the summer heat, while the east winds blowing over the continent have an opposite influence. It cannot be said that the climate is particularly good, owing to the changeableness of the weather, which may alter completely within a single day. The heavy atmosphere likewise, and the necessity of living within doors or in confined localities, cannot but exercise an influence on the character and temperament of the inhabitants. Only of certain districts, however, can it be said that they are positively unhealthy; to this category belong some parts of the Holland provinces, Zeeland, and Friesland, where the inhabitants are exposed to the exhalations from the marshy ground, and the atmosphere is often burdened with sea-fogs.

Fauna.—In the densely populated Netherlands, with no extensive forests, the fauna does not present any unusual varieties. The otter, martin and badger may be mentioned among the rarer wild animals, and the weasel, ermine and pole-cat among the more common. In the 18th century wolves still roamed the country in such large numbers that hunting parties were organized against them; now they are unknown. Roebuck and deer are found in a wild state in Gelderland and Overysel, foxes are plentiful in the dry wooded regions on the borders of the country, and hares and rabbits in the dunes and other sandy stretches. Among birds may be reckoned about two hundred and forty different kinds which are regular inhabitants, although nearly two hundred of these are migratory. The woodcock, partridge, hawk, water-ousel, magpie, jay, raven, various kinds of owls, wood-pigeon, golden-crested wren, tufted lark and titmouse are among the birds which breed here. Birds of passage include the buzzard, kite, quail, wild fowl of various kinds, golden thrush, wagtail, linnet, finch and nightingale. Storks are plentiful in summer and might almost be considered the most characteristic feature of the prevailing landscape.

Flora.—The flora may be most conveniently dealt with in the four physiographical divisions to which it belongs. These are, namely, the heath-lands, pasture-lands, dunes and coasts. Heath (Erica tetralix) and ling (Calluna vulgaris) cover all the waste sandy regions in the eastern division of the country. The vegetation of the meadow-lands is monotonous. In the more damp and marshy places the bottom is covered with marsh trefoil, carex, smooth equisetum, and rush. In the ditches and pools common yellow and white water-lilies are seen, as well as water-soldier (Stratiotes aloides), great and lesser reed-mace, sweet flag and bur-reed. The plant forms of the dunes are stunted and meagre as compared with the same forms elsewhere. The most common plant here is the stiff sand-reed (Arundo arenaria), called sand-oats in Drente and Overysel, where it is much used for making mats. Like the sand-reed, the dewberry bramble and the shrub of the buckthorn (Hippophae rhamnoides) perform a useful service in helping to bind the sand together. Furze and the common juniper are regular dune plants, and may also be found on the heaths of Drente, Overysel and Gelderland. Thyme and the small white dune-rose (Rosa pimpinellifolia) also grow in the dunes, and wall-pepper (Sedum acre), field fever-wort, reindeer moss, common asparagus, sheep’s fescue grass, the pretty Solomon-seal (Polygonatum officinale), and the broad-leaved or marsh orchis (Orchis latifolia). The sea-plants which flourish on the sand and mud-banks along the coasts greatly assist the process of littoral deposits and are specially cultivated in places. Sea-aster flourishes in the Wadden of Friesland and Groningen, the Dollart and the Zeeland estuaries, giving place nearer the shore to sandspurry (Spergularia), or sea-poa or floating meadow grass (Glyceria maritima), which grows up to the dikes, and affords pasture for cattle and sheep. Along the coast of Overysel and in the Biesbosch lake club-rush, or scirpus, is planted in considerable quantities for the hat-making industry, and common sea-wrack (Zostera marina) is found in large patches in the northern half of the Zuider Zee, where it is gathered for trade purposes during the months of June, July and August. Except for the willow-plots found along the rivers on the clay lands, nearly all the wood is confined to the sand and gravel soils, where copses of birch and alder are common.

Population.—The following table shows the area and population in the eleven provinces of the Netherlands:—

Province Area in
sq. m.		 Population
1890.		 Population
1900.		 Density per
sq. m. in
1900.
North Brabant 1,980 509,628 553,842 280
Gelderland 1,965 512,202 566,549 288
South Holland 1,166 949,641 1,144,448 981
North Holland 1,070 829,489 968,131 905
Zeeland 690 199,234 216,295 313
Utrecht 534 221,007 251,034 470
Friesland 1,282 335,558 340,262 265
Overysel 1,291 295,445 333,338 258
Groningen 790 272,786 299,602 379
Drente 1,030 130,704 148,544 144
Limburg 850 255,721 281,934 332
  Total 12,648 4,511,415 5,104,137* 404
* This total includes 158 persons assigned to no province.