696 The American Naturcdist. [Auo-ust, 



lake by evaporation. On the shores of these lakes would be 

 afforded a congenial place for the first plants, among which, no 

 doubt, sphagnum was prominent. The available food supplies 

 in the soil of the hills around was washed and afforded food 

 for these plants. As plants grew upon the hills, vegetable 

 humus accumulated, and the wash from this further enriched 

 the soil at the shore. But while this washing contributed 

 something to the accumulations of the swamp, it, under no 

 circumstances, can be compared to the soil washed down upon 

 the flood plains of upland streams, and for the reason that 

 these streams are not rapid enough to carry much solid ma- 

 terial. The accumulations in the swamps are almost entirely 

 the decayed plants that have grown there. 



ABILITY OF THE LAKE TO RESIST INVASION. 



The factors which determine the ability of the lake to resist 

 invasion are its depth and the character of its shores. If the 

 conditions are right, a lake even of considerable depth will be 

 steadily encroached upon by vegetation. On the other hand 

 a shallow lake will grow over much more rapidly. There is 

 a popular notion that a cranberry bog may grow right over a 

 lake, and that the flexible turf is like a blanket spread over 

 the surface of the water. Walking on these places certainly 

 gives one that impression. I have never seen a case where 

 this was the actual condition of affairs. If you penetrate the 

 turf anywhere you will find the blackest and softest kind of 

 mud, almost as mobile as water, but as a plant food much 

 more nutritious. From a boat there sometimes appear deep 

 recesses far under the turf, but these are more apparent than 

 real. There are often recesses under the turf, just as there are 

 under harder shores, but these are not deep, and I feel reason- 

 ably sure that the floating moors float upon mud rather than 

 upon water. 



THE EFFECT OF WIND UPON THE RELATIVE POSITION OF LAKE 



AND BOG. 



The position of the lake, with reference to other parts of the 

 swamp has attracted my attention for some time. The lakes 

 in the northern and western parts of Oswego County have, as 



