BEAVER DAMS-FORMATION OF BOGS. 
31 
production and deposit, then very often restored to the forest 
condition by the growth of black ashes, cedars, or, in southern 
latitudes, cypresses, and other trees suited to such a soil, and 
thus the interrupted harmony of nature is at last reestablished. 
I am disposed to think that more bogs in the Northern 
States owe their origin to beavers than to accidental obstruc¬ 
tions of rivulets by wind-fallen or naturally decayed trees ; for 
there are few swamps in those States, at the outlets of which 
we may not, by careful search, find the remains of a beaver 
dam. The beaver sometimes inhabits natural lakelets, but he 
prefers to owe his pond to his own ingenuity and toil. The 
reservoir once constructed, its inhabitants rapidly multiply, 
and as its harvests of pond lilies, and other aquatic plants on 
which this quadruped feeds in winter, become too small for 
the growing population, the beaver metropolis sends out 
expeditions of discovery and colonization. The pond grad¬ 
ually fills up, by the operation of the same causes as when it 
owes its existence to an accidental obstruction, and when, at 
last, the original settlement is converted into a bog by the 
usual processes of vegetable life, the remaining inhabitants 
abandon it and build on some virgin brooklet a new city of 
the waters. 
In countries somewhat further advanced in civilization 
than those occupied by the North American Indians, as in 
mediaeval Ireland, the formation of bogs may be commenced 
by the neglect of man to remove, from the natural channels 
of superficial drainage, the tops and branches of trees felled 
has a thickness of four metres, and some of them, at first lower than 
the sea, have been thus raised and drained so as to grow summer crops, 
such, for example, as maize.”— Boitel, Mise en valeur des Torres pauvres , 
p. 227. 
The bogs of Denmark—the examination of which by Steenstrup and 
Yaupell has presented such curious results with respect to the natural suc¬ 
cession of forest trees—appear to have gone through this gradual process 
of drying, and the birch, which grows freely in very wet soils, has con¬ 
tributed very effectually by its annual deposits to raise the surface above 
the water level, and thus to prepare the ground for the oak.— Vaupell, 
Bogens Indvandring, pp. 89, 40. 
