864 FLOATING OF TIMBER. 
Another evil, sometimes of serious magnitude, which attends 
the operations of the lumberman, is the injury to the banks of 
rivers from the practice of floating. Ido not here allude to 
rafts, which, being under the control of those who navigate 
them, may be so guided as to avoid damage to the shore, but 
to masts, logs, and other pieces of timber singly entrusted to 
the streams, to be conveyed by their currents to sawmill ponds, 
this theory cannot be admitted upon the evidence in question. In fact, the 
order of succession—for a rotation or alternation is neither proved nor 
probable—may be made to move in opposite directions in different countries 
with the same climate and at the same time. Thus in Denmark and in Hol- 
land the spike-leaved firs have given place to the broad-leaved beech, while in 
Northern Germany the process has been reversed, and evergreens have sup- 
planted the oaks and birches of deciduous foliage. The principal determining 
cause seems to be the influence of light upon the germination of the seeds 
and the growth of the young tree. In a forest of firs, for instance, the dis- 
tribution of the light and shade, to the influence of which seeds and shoots 
are exposed, is by no means the same as in a wood of beeches or of oaks, and 
hence the growth of different species will be stimulated in the two forests. 
When ground is laid bare both of trees and of vegetable mould, and left to 
the action of unaided and unobstructed nature, she first propagates trees 
which germinate and grow only under the influence of a full supply of light 
and air, and then, in succession, other species, according to their ability to 
bear the shade and their demand for more abundant nutriment. In Northern 
Europe the larch, the white birch, the aspen, first appear; then follow the 
maple, the alder, the ash, the fir; then the oak and the linden; and then the 
beech, The trees called by these respective names in the United States are 
not specifically the same as their European namesakes, nor are they always 
even the equivalents of these latter, and therefore the order of succession in 
America would not be precisely as indicated by the foregoing list, but, so far 
as is known, it nevertheless very nearly corresponds to it. 
It is thought important to encourage the growth of the beech in Denmark 
and Northern Germany, because it upon the whole yields better returns than 
other trees, and does not exhaust, but on the contrary enriches, the soil; for 
by shedding its leaves it returns to it most of the nutriment it has drawn from 
it, and at the same time furnishes a solvent which aids materially in the de- 
composition of its mineral constituents, 
When the forest is left to itself, the order of succession is constant, and its 
occasional inversion is always explicable by some human interference. It is 
curious that the trees which require most light are content with the poorest 
soils, and vice versa. The trees which first appear are also those which pro- 
pagate themselves farthest to the north. The birch, the larch, and the fir 
