62 LAKES OF NORTH AMERICA. 



lion tons in excess of the combined foreign and coastal trade of London 

 and Liverpool. 



The demand for still better facilities for inter-lake commnnication has 

 led to the construction of still larger canals and locks, and now improve- 

 ments are nearly completed which will allow vessels drawing 21 feet of 

 water to pass from Buffalo to Duluth. It is expected that when this 

 improvement is made the trade between Lake Supeiior and the more 

 southern lakes will be doubled in a few years. Far-reaching plans for 

 connecting this important commercial industry with ocean highways are 

 under consideration, and must tind consummation in the near future. 



The fisheries of the Laurentian lakes is another subject of great prac- 

 tical importance, as they are the most extensive lake fisheries in the 

 world. The lakes abound in trout, whitefish, and other food fishes, and 

 their shores are dotted with fishing villages, in which a hardy population, 

 skilled in all that pertains to their calling, are living their humble but 

 useful lives, and gaining an experience which well fits them for naval 

 service should their aid be called for. The importance of these inland 

 fisheries has received tardy recognition in comparison with the similar 

 industries of the sea border, but they are a substantial element of national 

 wealth and claim the most careful attention and guidance of both state 

 and national legislators. The reports of the U. S. Fish Commission show 

 that over ten thousand persons are engaged in this industry ; that the 

 capital invested is in excess of four and one-half millions of dollars ; and 

 that a hundred million pounds of fish are secured each year, which bring to 

 those actually engaged in the work more than two and one-half millions 

 of dollars. 



It may be noted as an item of interest in connection with the physical 

 history of the Laurentian basin, that in lakes Superior and Michigan crus- 

 taceans and fishes have been found that are believed to be identical with 

 living marine forms. These are thought by some persons to indicate that 

 the lakes in which they occur were formerly in open communication with 

 the ocean. Considerable evidence, derived from a study of the former 

 extent of the lakes, and of the fossils in the sediments of previous 

 water-bodies in the same basins, do not seem to confirm this conclusion, 

 however, and further study of the habits and means of migration of the 

 species referred to, is necessary before their presence in inland waters can 

 be satisfactorily accounted for. 



The movements of the waters of the Laurentian lakes and a few facts 

 respecting their temperature and tlieir ii'fluence on the climate of the 



