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 considerable; thus the evaporation per second on Huron and Michigan, as given in the table above, is nearly 67,000 ft., but the figures for another year show nearly 89,000 ft. per second, which would represent a difference of 61/2 in. in water level.  As a discharge of 10,000 cubic feet a second into the new canal would lower the level of these two lakes by 2.87 in. in a year, it follows that the difference between a year of maximum and one of minimum evaporation is more than twice as great as would be required for the canal, and even under the most unfavorable conditions the volume taken from the whole chain of lakes would not lower them an inch.