Perry.] 140 [February 28, 
Although such remains continued to be laid down at a later day,— 
though they find place in limited quantities even in the present,— 
their deposition has been comparatively small ever since the Marl 
period proper came to a close. At about this time, lakes and ponds 
in great numbers were undergoing a change. They had come to be 
to a considerable extent filled; while bogs and morasses, in a large 
measure, took their places. Accordingly there is a more recent de- 
posit, which we find in many places, lying above the marl beds. The 
instances exceptional to this statement are so few as to be scarcely 
deserving of notice, unless it be for their rarity, and the lhght they 
are calculated to throw on a predominant process of an earlier day. 
We thus see that the way was gradually prepared for a change in 
the prevailing order of things. 
§2. The Peat Period. 
Answering to this designation is what might be termed the Newer 
Holocene. The ponds and small lakes, which at an earlier day evi- 
dently prevailed in great numbers, having been gradually filled, the 
life with which they had swarmed weuld cease to be predominant in 
them, since the requisite conditions were wanting to its support, in 
its pristine exuberance and vigor. This change we should not ex- 
pect to occur everywhere, at precisely the same point of time ; while, 
in some cases, ponds and lakes would remain to a considerable extent 
unfilled. ‘Thus, in isolated instances, the conditions might not be 
materially different from what they had been, and fresh-water mol- 
lusks no doubt continued to flourish in restricted areas. On the 
whole, however, there is evidence of such a change as has been re- 
ferred to. After its occurrence, and in connection with it, morasses, 
swamps and bogs came to prevail very extensively, and with them 
the manifold growths peculiar to such a state of things. These were 
various species of sphagnum and several other kinds of swamp 
mosses and plants. There would accordingly be laid down, as time 
passed on, large quantities of vegetable matter—broad and thick 
accumulations of bog-mosses that grew, and from generation to gen- 
eration took their places as deposits—which are now known as peat- 
beds. ‘These, in many cases, cover extensive areas; ordinarily they 
are more remarkable for their frequency, than for their superficial 
extent; while they usually vary in thickness from a few inches to 
some twenty-five or thirty feet; they are known in rare instances to 
reach sixty feet. Thus the growth must have been exuberant. Peat, 
