692 The American Naturalist. [August, 
blue hardpan, very impervious to water, and we may suppose 
that as the water in post-glacial times receded, every depres- 
sion was left full of water. Many were shallow and were soon 
filled to the brim with vegetable mould; others were deeper 
and are even now barely full, while some still contain lakes 
which the invading plant-life is constantly making smaller. 
There are presented here all gradations between wooded 
swamps and open lakes. Some swamps, now mostly wooded, 
as for example, the Wine Creek swamp near Oswego, still have 
sphagnum persisting in them, and are, no doubt, lakes filled 
only at a comparatively recent date, while the vegetable ac- 
cumulations are so shallow in other wooded swamps as to lead 
one to believe that the ponds which originally occupied them 
were relatively soon displaced. 
Not only does the contour of the country in the northern 
part of. the county determine the flow of the streams, but it 
likewise determines the form of the lakes‘and swamps. They 
are, so far as I am aware, always elongated in a northerly and 
southerly direction, some of them being several miles long and 
less than a mile wide. 
; TYPICAL SWAMPS. 
I have selected three swamps from the score or more within 
the limits of the county, not because they illustrate better than 
others the observations to be recorded, but rather because they 
illustrate swamps in different stages of maturity. I have 
already hinted at what is meant by the maturity of a swamp- 
The woodéd swamps with shallow accumulations of vegetable 
material, sometimes called muck, matured early in the post- 
glacial history of the region. Some are just coming to matur- 
ity, examples of which have already been cited, and there are 
still others which are maturing, but will still require many 
years for their completion. 
For want of a better term I have used the word swamp in 
an extended sense to indicate the whole depression, whether it 
be covered with water, woods or moor. 
MUD LAKE. 
Mud Lake is situated in the southwestern corner of the tow? 
of Oswego. It is about eight miles southwest of Oswego City, 
