of the total amount that now passes
through the St. Clair River and thence over Niagara.
The following table gives some particulars of the great lakes and the
discharge from them:
---------------+----------+-------+--------+-----------------------
| | | |Cubic Feet per Second.
|Elevation |Area of| Area of+-------+-------+-------
| above | Basin,| Lake, | | |
Lake. |Mean Tide.| Square| Square| Rain- |Evapo- | Dis-
| Feet. | Miles.| Miles.| fall. |ration.|charge.
| | | | | |
---------------+----------+-------+--------+-------+-------+-------
| | | | | |
Superior | 601.78 | 90,505| 38,875 |187,386| 34,495| 80,870
Huron and Mich.| 581.28 |121,941| 50,400 |262,964| 66,754|216,435
Erie | 572.86 | 40,298| 10,000 | 96,654| 13,870|235,578
Ontario | 246.61 | 31,558| 7,220 | 75,692| 10,568|272,095
| | | | | |
---------------+----------+-------+--------+-------+-------+-------
The average variation in level of the lakes is from 18 in. to 24 in.
during the year, and the range in evaporation from year to year is
also very considerable; thus the evaporation per second on Huron and
Michigan, as given in the table above, is nearly 67,000 ft.
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