60 



LAKES OF NORTH AMERICA. 



by an analysis of the Avater of St. Lawrence river taken near Montreal. 

 This analysis may also be considered as representing very nearly the com- 

 position of the material carried in solution by the lakes and rivens of the 

 more humid portions of North America.^ 



AxALYSis OF THE AVatp:r OF St. Laavrexce River. 

 By T. Steery Hunt.- 



Taking the volume of the St. Lawrence at 300,000 cubic feet per 

 second, the computed discharge of Lake Ontario, it follows from the above 

 analysis that approximately 1.5 tons of mineral matter in solution is trans- 

 ported by it per second, or about 50 million tons annually. 



Erosion of the lake shores. — The shores of the Laurentian lakes 

 are being eroded at many localities, and the material thus removed de- 

 posited, in part, on otlier portions of the coast so as to add to the land 

 area. Some information in this connection has been compiled l)y Charles 

 Crosman," but mucli additional data is required before general conclusions 

 of value can be reached. 



The average annual recession of the sea-cliff along the west side of 

 Lake ^Michigan, as determined by Prof. Edward Andrews from a some- 

 what extended series of observations, is stated to be about 5 feet ; Avith a 



1 Analyses of the water of 20 rivers of the Ignited States and Canada may be found in 

 Monograph Xo. XI, U. 8. Geological Survey, Table A. 



2 Geological Survey of Canada, 1863, p. 507. 



3 "Chart of the Great Lakes." Published at Milwaukee, Wisconsin. 



