M 
3 
1 
2 
3 
4 
5 
6 
1 
8 
9 
10 
11 
72 
73 
74 
75 
76 
77 
78 
19 
20 
21 
Birge—Work of Wind in Warming a Lake. 
389 
70 
20 
30 
40 
50 
60 
70 
Plate X 
