298 J. D. Dana on the Origin of Prairies. 
when frozen over in winter; and still they are covered with 
orests 
The soil of these lower flats is often the finest of silt, such as © 
naturally belongs to bogs and lakes; and varies from this on 
one side to peat, and on the other to sandy loam; and that of 
the upper terraces and hills varies from sandy loam to gravel 
and the coarsest and hardest of drift-material. Yet all these 
different kinds of soil are covered alike with forests. There are 
runs out on the bog almost as far as the larch, is not here 
counted, it being regarded as a shrub. The “Cedar” (Arbor- 
vite) swamps, which are the remnants of the very exteusive 
ones of Parishhill and Sangerfield, and from which the cedar 
as been cut out, and which are gradually drying, are already 
becoming filled with black ash, with a sprinkling of red maple, 
and especially of elm. : 
The great lake regions of Maine afford facts of similar import. 
I cite the following from observations made the last summer, at 
the suggestion of the writer, by Prof. A. E. Verrill, of one ¥ 
in Maine, (now of Yale College), and communicated b 
(from Westport, N. Y., on Lake Champlain,) for this article: 
“The points which I had in view in my observations were the following 
Ist, the succession of vegetation as a lake changes to a swamp, and t 
to dry land; 2nd, when swamps become permanently flooded what 
changes occur in the vegetation; 3d, when lakes or swamps are drained 
be) 
: There are in Maine abundant opportunities for studying almost every 
~~ 
