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 wooded 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 town 

 of Oswego. It is about eight miles southwest of Oswego City, 



