A NEW EVAPORATION FORMULA 
31 
October in the years used in this investigation, 1909 to 1913 inclusive, h was prac- 
tically constant at 0.005 foot per day. Its extreme range was from 0.003 foot to 
0.006 foot of depth on Lake Michigan-Huron. 
Lake Superior being the highest lake in the series, there was no inflow into it 
in the sense here meant, the inflow from Lake Nipigon being considered as part of 
the run-off into the lake, and therefore included in the /c-term of the observation 
equations for that lake. 
Table 12. — Compilation of It, Lake Michigan- Huron 
Date 
Water levels at Sault Ste. Marie 
(above locks) 
600. + ft. 
Discharge of 
St. Mary's River 
(/s) 
1910 
Sept. 1 
1.50 
1.28 
1.63* 
1.59 
1.41 
1.51 
1.38 
1.75 
1.71 
1.47 
1.46 
1.74 
1.51 
1.57 
1.49 
1.42 
1.43 
1.47 
1.39 
1.53 
1.55 
1.15 
1.39 
1.16 
1.48* 
1.16 
1.50 
1.38 
1.23 
1.30 
1.89 
1.17 
1.08 
1.39 
1.61 
1.68 
1.23 
1.59 
1.66 
1.42 
5 
5 
5 
5 
6 
5 
6 
5 
5 
5 
5 
5 
6 
5 
5 
5 
5 
5 
6 
5 
5 
4 
5 
4 
5 
4 
5 
5 
4 
6 
5 
4 
4 
5 
5 
5 
4 
5 
5 
5 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
Oct. 1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
* Interpolated values, or partially uncertain values. 
EXAMPLE OF COMPUTATION OF A. LAKE MICHIGAN-HURON 
The quantity, I 4 , for Lake Michigan-Huron is the computed fall of the lake 
surface due to the outflow from the lake into Lake St. Clair through the St. Clair 
River. This outflow is given by equation (6), in 0.001 foot of depth on Lake 
Michigan-Huron, as a function of the slope of the water surface between Harbor- 
Beach and the St. Clair Flats Canal. The first two columns in Table 13 show the 
