DRAINING OF THE LAKE OF HAARLEM. 
349 
mass together. This operation was completed in 1848, and 
three steam pumps were then employed for five years in dis¬ 
charging the water. The whole enterprise was conducted at 
the expense of the state, and in 1853 the recovered lands were 
Nederlandl, 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 he subject to 
frequent agitation by the wind. For example, not a single 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, their area 
is sufficiently enlarged to be much acted on by wind. When still water 
above a yard deep is left undisturbed, aquatic plants of various genera, 
such as Nuphar, Hymphsea, 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, Spar- 
ganium, Rumex, Lythrum, Pedicularis, Spiraea, Polystichum, Comarum, 
Caltha, &c., &c. 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 sur¬ 
face, bearing with it, of course, the soil formed above it by decay of stems 
and leaves. Hew genera now appear upon the mass, such as Carex, Men- 
vanthes, 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 Overijssel, Jcrag; and in Holland, 
rietzod. It floats about as driven by the wind, gradually 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 in¬ 
vaded in the mean time by men or cattle, trees and arborescent plants, 
Alnus, Salix, Myrica, &c. appear, and these contribute to hasten the attach¬ 
ment of the turf to the bottom, both by their weight and by sending their 
roots quite through into the ground. 
This is the regular method employed by nature for the gradual filling 
up of shallow lakes and pools, and converting them first into morass and 
then into dry land. When ver therefore man removes the peat or turf, he 
exerts an injurious geographical agency, and, as I have already said, there 
is no doubt that the immense extension of the inland seas of Holland in 
modern times is owing to this and other human imprudences. “Hundreds 
of hectares of floating pastures,” says our author, u which have nothing in 
their appearance to distinguish them from grass lands resting on solid bog, 
