RIVER AND LAKE DEPOSITS 191 
to swamps, while not a few are almost completely 
choked. In this region may be seen every stage in the 
final destruction of lakes by the aid of plant growth. 
One form of plant is of particular importance in 
this respect. A moss, the sphagnum, grows luxuriantly 
on the shores of these tiny ponds and lakelets; and 
Fie. 100. 
A peat bog in the Adirondacks with a pond enclosed — the last remnant of the 
former lake. (Copyrighted, 1888, by S. R. Stoddard, Glens Falls, N.Y.) 
by its life and death, builds a bog which is sometimes 
several feet in depth. Little by little it narrows the 
area of water (Fig. 100) and finally destroys it, in the 
last stage becoming a quaking bog, owing to the fact 
that the peat is growing over the surface of the remain- 
ing muddy water (Fig. 101). Such bogs are dangerous 
because the moss is growing as a thin sheet over water, 
