420 DRAINING OF THE LAKE OF HAARLEM. 
pact the mass together. This operation was completed in 1848, 
and three steam-pumps were then employed for five years in 
discharging the water. The whole enterprise was conducted at 
the expense of the state, and in 1853 the recovered lands were 
offered for sale for its benefit. Up to 1858, forty-two thousand 
acres had been sold at not far from sixteen pounds sterling or 
of Germany the floating islands, covered with trees, which met the Roman 
fleets at the mouths of the Elbe and the Weser. Ourauthor speaks also of 
having visited, in the territory of Bremen, floating moors, bearing not only 
houses but whole villages. Atlow stages of the water these moors rest upon 
a bed of sand, but are raised from six to ten feet by the high water of spring, 
and remain afloat until, in the course of the summer, the water beneath is 
exhausted by evaporation and drainage, when they sink down upon the sand 
again. 
Staring explains, in an interesting way, the whole growth, formation, and 
functions of floating fens or bogs, in his very valuable work, De Bodem van 
Nederland, i., pp. 36-43. The substance of his account is as follows: The 
first condition for the growth of the plants which compose the substance of 
turf and the surface of the fens, is stillness of the water. Hence they 
are not found in running streams, nor in pools so large as to be subject to 
frequent agitation by the wind. For example, not asingle plant grew in the 
open part of the Lake of Haarlem, and fens cease to form in all pools as soon 
as, by the cutting of the turf for fuel or other purposes, theiz area is suffi- 
ciently enlarged to be much acted on by wind. When still water aboye a 
yard deep is left undisturbed, aquatic plants of various genera, such as Nu- 
phar, Nymphea, Limnanthemum, Stratiotes, Polygonum, and Potamogeton, 
fill the bottom with roots and cover the surface with leaves. Many of the 
plants die every year, and prepare at the bottom a soil fit for the growth of 
a higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex, 
Lythrum, Pedicularis, Spirea, Polystichum, Comarum, Caltha, etc., ete. In 
the course of twenty or thirty years the muddy bottom is filled with roots of 
aquatic and marsh plants, which are lighter than water, and if the depth is 
great enough to give room for detaching this vegetable network, a couple of 
yards for example, it rises to the surface, bearing with it, of course, the soil 
formed above it by decay of stems and leaves. New genera now appear upon 
the mass, such a Carex, Menyanthes, and others, and soon thickly cover it. 
The turf has now acquired a thickness of from two to four feet, and is 
called in Groningen lad ; in Friesland, til, tilland, or drijftil ; in Overijsse', 
krag ; and in Holland, rietzod. It floats about as driven by the wind, grad- 
ually increasing in thickness by.the decay of its annual crops of vegetation, 
and in about half a century reaches the bottom and becomes fixed. If it 
has not been invaded in the meantime by men or cattle, trees «nd arborescent 
