2 TRANSACTIONS OF THE CANADIAN INSTITUTE. {[VoL. VIII. 
has been completed by the United States Army Engineers, the results 
of the survey being as follows :— 
; Area of Water Area of Water Aggregate Area 
Lakes. Surface—Square Shed—Square of Basin—Square 
Miles, Miles, Miles. 
Lake SUPEMOL sc sca trite eere 31,200 51,600 82,800 
Saint: Mary ssRIver. 2 co. «sees 150 800 950 
Lake Michigan... 02): 2 .\rcteciee 22,450 37,700 60,150 
Lake Huron and Georgian Bay.. 23,800 31,700 55,500 
saint iGlair URivet....5 3-02) siseier= 25 3,800 39825 
ake, saint (Clair. ).;2: 0%. solace 410 3,400 3,810 
DPE OIDIRIVED Shs aoe seme oe 25 1,200 1,225 
AK ECE ME. ii ecrs sce iaee en ee 9,960 22,700 32,660 
INNA ATA INIVEE Metasele lsc. ejtns ee eins 15 300 315 
Make ‘Ontario. Rie secs ec tc tee ee 7,240 21,600 28,840 
Motalse. fesdctse ses sces 95,275 174,800 270,075 
The levels of the mean surfaces of the lakes above the mean sea level 
at Governor’s Island, New York, are: Lake Ontario, 2467 feet ; Lake 
Erie, 57210 ; Lakes Huron and Michigan, 58170 feet; and Lake Su- 
perior, 601%0 feet. The difference of 20} feet between Lakes Superior 
and Huron occurs in the rapids of Saint Mary’s River, the 815 between 
Lakes Huron and Erie, mainly in the Detroit River. The difference of 
326 feet between Lakes Erie and Ontario occurs in the vicinity of 
Niagara Falls, and is principally grouped as follows: 100 feet in the 5 
_miles of rapids between Lewiston and the Lower Suspension Bridge; 
10 feet in the rapids between the bridge and the falls; 160 feet at the 
falls; 50 feet in the rapids immediately above the falls, and 6 feet in the 
Upper Niagara River. 
The mean depth of Lake Superior is about 475 feet, the deepest point 
marks a depth of 1,008 feet, or 406 feet below the level of the sea. Lake 
Huron has a mean depth of about 250 feet, and a maximum depth of 
750 feet. Lake Michigan has a mean depth of 325 feet, and a maximum 
depth of 870 feet. Lake Erie is comparatively shallow, having an aver- 
age depth of less than 70 feet, and a maximum depth of 210 feet. Lake 
Ontario has a mean depth of about 300 feet, and a maximum of 738 
feet, or nearly 500 feet below sea level. The channels of the rivers con- 
necting the lakes seldom exceed 50 feet. According to the United 
States lake surveys, the mean actual rain and melted snowfalls of the 
several lake basins are: Lake Superior, 29 inches; Lake Huron, 30 
inches; Lake Michigan, 32 inches ; Lakes Erie and Ontario, 34 inches. 
This is about equal to 31 inches on the entire lake basin. The following 
represent the average discharges of the lakes: Lake Superior, at Saint 
