CHARACTERISTICS AND DISTRIBUTION OF LAKES 625 
but owing to changes in the rivers connecting the various lakes, and also 
on account of the many harbour and canal improvements tliat have 
been carried out, a new survey of portions of the lakes has been made 
under the direction of General O. M. Poe. From the results of the 
former survey L. Y. Schermerhorn ^ has compiled some statistics 
regarding the Great Lakes, a few of which are quoted here ; the 
measurements of the length and breadth of the various lakes not 
being given by Schermerhorn, those given by S. E. Dawson ^ are 
for the most part adopted. 
Lake Superior, the largest body of fresh water on the globe, 627 
feet above sea-level, has an area of about 31,200 square miles, a mean 
depth of 475 feet, and a maximum depth of 1008 feet. The length 
is about 400 miles, the circumference about 1500 miles, the maximum 
breadth about 160 miles. At depths exceeding 200 feet the tem- 
perature of the lake varies only slightly from 39° Fahr. (3° '9 C.) 
all the year round. 
Lake Michigan has an area of 22,450 square miles, a mean depth 
of 325 feet, and a maximum depth of 870 feet ; its surface is 581 feet 
above sea-level. The length is 345 miles, the maximum breadth 
about 90 miles. 
Lake Huron, together with Georgian Bay, covers an area of 23,800 
square miles. It has a mean depth of 250 feet, a maximum depth of 
730 feet, and lies at the same altitude as Lake Michigan. It is 270 
miles in length, and exceeds 100 miles in breadth. The temperature 
of the lake in the months of June and August at the surface and at 
depths of about 300 feet was 52° Fahr. (11°-1 C), while at a depth 
of 624 feet the temperature was 42° Fahr. (5° '6 C). 
Lake Erie has a water surface of 9960 square miles, a mean depth 
of about 70 feet, a maximum depth of 210 feet, and lies at an 
altitude of 573 feet. The length is 250 miles, the maximum breadth 
about 58 miles. 
Lake Ontario covers an area of 7240 square miles, has a mean 
depth of about 300 feet, a maximum depth of 738 feet, and lies 247 
feet above sea-level. The surface is subject to periodical variations 
amounting to about 3 5 feet. It is 190 miles in length, and 55 
miles in maximum breadth. 
Lake St Clair, a much smaller lake lying between Lakes Huron 
and Erie, covers an area of 410 square miles, has an average depth 
of 15 feet, and lies 570 feet above sea-level; the length is 30 miles, 
and the maximum breadth 20 miles. 
1 See " Physical Characteristics of the Northern and North-Western Lakes,'^ 
Amer. Joimi. Sci., ser. 3, vol. xxxiii. p. 278, 1887. 
2 See Stanford's Compendium of Geograjohij : North America, vol. i, p. 34, 
London, 1897. 
40 
