RELATION OF LAKES To (•LL^L\TI(■ CONIHTloNS. Gl 



maximum at certain localities, of IG feet. In the nciglihoiliood of Cleve- 

 Luul, Ohio, the mean recession of a line of prominent sea-cliffs in boulder 

 clay, for a period of 40 years, has ])vcn al)out G feet per aiiiuim. 



()l)scrvations at less favoral)le localities show a simihir retreat of 

 other p(»rtioiis of the lalce shores, l)ut detinite (|uantitative observations 

 have si'ldom been recorded. Eii(inL;ii is known in a (jualitative wa}-, how- 

 ever, to show that important changes in the outlines of these lakes are in 

 progress. The waste of the shore, resulting in a broadening of. the sur- 

 faces of the lakes, is compensated in part by the deposition of the material 

 removed on adjacent area so as to extend the land lakeward, as, for 

 example, at the south end of ]>ake ]\Iichigan, where beaches and large 

 sand dunes have been formed, and are still encroaching on the lake. 

 ( )bservations made by the writer at various localities about the shores of 

 the lakes, together with the reports of others, show conclusively that the 

 process of broadening the lakes by the erosion of their shores is progress- 

 ing more rapidly than areas are being leclaimed by deposition, and there- 

 fore that they are becoming shallower. 



Comiuerce ami lisherics. — The importance of the Laurentian lakes 

 as highway's of commerce is too well known and is too extended a sul)ject 

 to receive treatment at this time, even if it fell within the scope of the 

 present discussion. Some idea of the magnitude of the commerce on 

 these inland waters may l)e had, however, from the reports of the opera- 

 tion of the Government locks at Sault St. ]\Iarie, whit'li sliow that ll.ooT 

 vessels passed through them during the year ending June 30, 1802. car- 

 rying over 10 million tons of freight. The great importance of the com- 

 merce of the Laurentian lakes will be better appreciated, by those A\ho 

 are not familiar witli it. when it is compared witli the trailic of the Snez 

 Canal. In 1880, tlie latest date at which comi)arative data are at hand, 

 nearly three times as many vessels passed through the locks at Sault St. 

 Marie as tlndUL!li tlie Suez Canal, althoufjli the latter is oixmi for navi^-a- 

 tion throughout the entire yeAv. The tonnage during the same year was 

 7.221,935 at the "Sou," as against G,783,189 for the Suez Canal. The 

 importance of the carrying trade of the Great Lakes is also shoA\ ii by the 

 fact that tlic tonnage of vessels constructed on them each vcar for several 

 yi ars, has l)een alxtut e(iual to that of all the vessels built on the Atlantic. 

 Pacilic, and (iulf coasts. Still moic st liking is the fact that the amount 

 of goods canic(l each year on these inland waters, is far in excess of the 

 entire clearances of all the scapoits of the I'nitcd States, and several mil- 



