tified rivers in the United States.

The following figures, showing the tonnage carried in 1888-89, give
some idea of the volumes of water-borne traffic in America:

Tons.
Detroit River 19,099,060
Erie Canal 5,370,369
Sault Ste. Marie 7,516,022
Welland Canal 828,271
St. Lawrence Canal 1,500,096
Mississippi to New Orleans 3,177,000
" below St. Louis 845,000
Ohio 2,236,917
Chicago Canal and lake 11,029,575

Except on the Mississippi, it may be reckoned that navigation is
closed by ice during five months a year. It may be mentioned, by way
of comparison, that the traffic on the Suez Canal during the year
1888-89 was 6,640,834 tons.

One very interesting point in connection with this work is the effect
that the diversion of so large a body of water from the lakes will
have upon their _regime_. At least 10,000 cubic feet a second would be
taken from Lake Michigan and find its way into the Mississippi; this
is approximately 41/2 per cent. 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