INFLUENCE OF THE FOREST ON INUNDATIONS. 227 
in all large agricultural districts, and lienee, even if, in tlie 
case we are supposing, the open ground chance to have been 
thawed before the melting of the snow which covers it, it is 
already saturated with moisture, or very soon becomes so, and, 
of course, cannot relieve the pressure by absorbing more water. 
The consequence is that the face of the country is suddenly 
flooded with a quantity of melted snow and rain equivalent to 
a fall of six or eight inches of the latter, or even more. This 
runs unobstructed to rivers often still bound with thick ice, 
and thus inundations of a fearfully devastating character are 
produced. The ice bursts, from the hydrostatic pressure from 
below, or is violently torn up by the current, and swept by 
the impetuous stream, in large masses and with resistless fury, 
against banks, bridges, dams, and mills erected near them. 
The bark of the trees along the rivers is often abraded, at a 
height of many feet above the ordinary water level, by cakes 
of floating ice, which are at last stranded by the receding flood 
on meadow or ploughland, to delay, by their chilling influence, 
the advance of the tardy spring. 
The surface of a forest, in its natural condition, can never 
pour forth such deluges of water as flow from cultivated soil. 
Humus, or vegetable mould, is capable of absorbing almost 
twice its own weight of water. The soil in a forest of decid¬ 
uous foliage is composed of humus, more or less unmixed, to 
the depth of several inches, sometimes even of feet, and this 
stratum is usually able to imbibe all the water possibly result¬ 
ing from the snow which at any one time covers it. But the 
vegetable mould does not cease to absorb water when it be- 
comes saturated, for it then gives off a portion of its moisture 
to the mineral earth below, and thus is ready to receive a new 
supply ; and, besides, the bed of leaves not yet converted to 
mould takes up and retains a very considerable proportion of 
snow water, as well as of rain. 
In the warm climates of Southern Europe, as I have 
already said, the functions of the forest, so far as the disposal 
of the water of precipitation is concerned, are essentially the 
same at all seasons, and are analogous to those which it per- 
