62 HOLLAND [uEOLOGt. Haarlem lake, which are respectively -1O66, -12-46, 13 61, the Schieveen polder near Schiedam - 16 27, the polders at Wo 1 Brugge, the Bergschenhoek, and the Znidplas -16-86, -17-58, and -18-49. Of equal importance with the relief of the country is the geological composition of the soil. It is evident from the history of the origin of the land that Quaternary forma tions alluvium and diluvium must be well represented. In fact they constitute no less than 99 9 per cent, of the surface of the Netherlands, only ! per cent, thus remaining for all the older formations the Tertiary and the Secondary, including the extremely limited Jurassic. To the alluvial strata belong, in the first place, the fen (veen) strata, which are subdivided into low fens, high fens, marsh fens, and the " dalgronden" or "reclaimed high fens. " The low fens, which are found in Groningen, Friesland, Overyssel, North and South Holland, and North Brabant (about the Langstraat), have been formed of aquatic plants, and, in the upper layers, of moss ; their elevation is that of the mean sea-level ; from them the " short turf," the best quality of peat, is obtained by dredging, and, when the standing water which collects after the peat has been dug out has been drained off, they may be turned into very productive arable land. The subsoil, on which the fertility then depends, consists usually of clays and alluvial sand or dune strata, rarely of diluvial sand strata. These low fens extend to no less than 904,597 acres, or about 11 per cent, of the surface. The high fens, of which the greater part have been " disfenned" or stripped of peat, are found in Groningen, Friesland, Drenthe, Overyssel, and the Peel " or Marsh of North Brabant, in the more elevated plains or valleys. They have been formed of trees, heath-plants, and moss, and fur nish the softer, inferior kind of peat, the "long turf." As the removal of the peat has been followed by the construction of canals to carry off the standing water, the high fens are of course free from marshes, but, resting as they do almost everywhere on diluvial gravel and sand, they do not furnish so fertile a soil as the low fens. They comprise 226,107 acres, or only about 2 "8 per cent, of the surface of the country. The marsh fens are composed almost exclusively of a few species of sedge or carex, and constitute, not only in their method of formation, but also in their character and situation, the transition between the high and the low fens. They are widely scattered, especially along small streams which carry off water mingled with fenny materials, and are nowhere more numerously represented than in Drenthe, where all the drainage is of this character. The marsh fens occupy 168,551 acres, consider ably less than the high fens. The " dalgronden" are formed where regular peat-fields are laid out along specially constructed canals, and the denuded surface is usually grubbed up for arable or pasture land, or on rare occasions planted with wood. They comprise about 207,576 acres, and naturally increase in proportion to the decrease of the high fens. We shall return to these " dalgronden" in con nexion with the canals. Besides the fens, the clay lands and cer- tain of the sand-strata belong to the alluvium. The clays which furnish the richest arable soils, the most luxuriant meadowland, and in some places the material for bricks and earthenware may be divided into the sea-clay, the river-clay, the stream-clay or green earth, and the old sea-clay of the districts recovered from the water. The exceptionally fertile sea-clay in the provinces of Groningen, Friesland, North and South Holland, and Zealand occupies no less than 1,676,860, or about 20 per cent, of the sur face, while the river-clay, naturally situated along the banks of the larger rivers, takes up 854,284 acres, or about 10 per cent. The boundary between the sea-clay and the river-clay is formed in the case of these rivers by the maximum high-water line. The stream- clay or green earth, which is found, as the former name implies, on the banks of the smaller rivers or streams, is formed of course on a much smaller scale, and consists of a stratum on an average from 3 to 5 feet thick, resting almost exclusively on the sand diluvium, from which it is occasionally separated by a fenny stratum. It occurs in the east of Drenthe, Overyssel, and Guelderland, along the _ small tributaries of the Vecht, along the Vecht, Regge, and Schipbeek in Overyssel, and in like manner in North Brabant along the Dommel, Aa, Mark, and other unimportant streams. The green Dearth not unfrequently contains iron ore; from this the metal is extracted in Overyssel and Guelderland, and it is asserted that in thirty years the natural processes replace the excavated mineral. The stream deposits occupy about 2 per cent, of the surface 157,187 acres. Finally the old sea-clay of the reclaimed districts covers 127,518 acres, or 1 per cent, of the surface. As already stated, the subsoil of the low fens is not everywhere clay. It is so in the main in the provinces of North and South Holland, where the drainage operations were consequently much more remunerative than in Friesland, and in the east of Utrecht, where the fens rested upon sand. Estimating the total area of the recovered districts at 197,690 acres, about five-eighths of this con sists of old sea-clay; and these portions, such as the Haarlem lake grounds, the Beernster and Purmer polders in North Holland, and the Nieuwkoop and Zuidplas polders in South Holland, are reckoned among the richest and most fertile. How these low-lying areas have been endyked and drained, surrounded by canals and kept dry by gigantic steam-pumps, has been explained under the heading HAARLEM LAKE. The alluvial sand-strata (to be distinguished from the diluvial Alluvii sand) may be divided into (1) sand-drifts, (2) river-sand, river- sand, downs, and " heibanen," and (3) old sea-sand and the sea-dunes with the Meat-grounds. The last of these classes has already been considered in dealing with the sea-coast. The rivers bring down their sand as well as their gravel, not so much from the more elevated districts as from the diluvial valleys in which they have excavated their channels. The beds of the rivers themselves consist likewise of sand, mingled here and there with gravel or rolled and polished pebbles, and, where the current is not too strong, covered with a layer of clay. If sand has been accumulated on the shore, the wind soon transforms it after the retreat of the river into hillocks or river-dunes. When these contain a propor tion of clay they are more fertile than the sea-dunes. They occur on both sides of the Guelderland Yssel (between Zalk and Oest), and on the Waal below Hulhuizen and opposite Rossum ; and various eminences in other parts of the country, such as Agnietenberg near Zwolle, and the heights near Deventer, near Grafthorst opposite Kampen, and along the Meuse between Venlo and Mook, must be considered as of similar origin. "Heibanen," i.e., heath-tracks, so called on account of their sterility, are beds of river gravel easily distinguished from the diluvial gravel by the smooth, worn, and j uniform appearance produced ages ago by the action of the current. They are found, for example, in the Betuwe, about Avezaat, and j between Lienden and Waddenoijen. Sand-drifts are dune forma tions originated by the action of the wind on the diluvial sand, where in one way or other it has been stripped of the heath-crust. They extend to 179,220 acres, or about 2| per cent, of the surface. The fen strata occupy in all 1,508,300 acres, or 18^ per cent. ; the clay strata 2,815,850 acres, or about 35 per cent. ; the alluvial sand strata 475,477 acres, or about 6 per cent. ; and the whole alluvium 4,799,627 acres, or 59 per cent. The diluvial or sand and gravel strata of the Netherlands are Diluvi; far from being of such economic importance as the alluvial strata, strata. The agricultural products mainly buckwheat and rye are neither so abundant nor so valuable as the wheat and rape-seed of the clay | soils; and neither stock-breeder nor dairy-farmer obtains so satis- j factory results. The boundary of the diluvial strata may be roughly indicated by a line running through Winschoten, Groningen, Dok- kum. Leeuwarden, Heerenveen, Steenwijk, Zwolle, Elburg, the coast , of the Zuyder Zee, Naarden, Utrecht, Rhenen, Bois-le-Duc, Breda, i Bergen-op-Zoom, and Antwerp. South and east of this line lies the diluvium, for the most part on the surface, except in the places , already mentioned where the fens, the river-clay, the stream deposits, and the sand-drifts are situated, or in the extreme south and east where the older strata make their appearance. To the north and west of the line the only diluvial strata are those of the Zuyder Zee islands : in Texel, Wieringen, and Urk the soil is of diluvial origin ; and this probably holds true also in whole or in part in Vlieland, Ameland, and Terschelling. The diluvial formations are subdivided into gravel-strata and sand-strata. To the former belong (1) the Scandinavian diluvium, in which occur granites and chalk flints derived from Scandinavia, situated to the north of the Overyssel Vecht (that is, in Groningen, Drenthe, the south-west of Friesland, and the islands); (2) the j mixed diluvium, which, besides the Scandinavian gravel contains ! stone-grit from Munster, the Teutoburger Wald, and the districts along the Rhine (it is situated between the Vecht and the Rhine, in Overyssel, Utrecht, the Gooiland, 1 and Guelderland); (3) the Rhine diluvium, destitute of granite, but with many fragments of white quartz, basalt, and other kinds of stone from the mountains along the river between Bonn and Cobleiitz (it lies between the Waal and the Meuse) ; (4) the Meuse diluvium, containing materials brought from the mountains higher up the stream; and finally (5) the Limburg flint diluvium, like the preceding variety desti tute of any plutonic or volcanic rocks, but nevertheless consist ing almost exclusively of flints occurring in the neighbouring chalk formation. The sand-diluvium, which is of later date than the gravel, is found in great level stretches at the foot of the hills of diluvial gravel, and contains no pebbles or coarse gravel. It also occurs in the maritime provinces under all the marine and fluvial formations. According to some authorities it owes its origin to the influence of rain, or frost, or wind ; according to others it has been formed by the sea like the Kempen sand and that of the dunes, and then transported by the south-westerly currents. 1 A district formerly called Naardingerland, on the southern shores of the Zuyder Zee, including Naarden, Bussum, Huizen, Blaricum,
Laren, Hilversum, and Muiderberg.
