GEOLOGY OF THE NORTH-WEST OF LAKE SUPERIOR. 



221 



■degraded. The Gulf of Mexico is being further filled up, along its 

 northern border. The banks of Newfoundland are still being added 

 to by the cargoes of northern iceVjergs. The impediments to the 

 outflow of inland waters by the St. Lawrence are still being removed, 

 for the St. Lawrence rapids, Niagara, the Sault Ste. Marie, are still 

 wearing away. In due time there will be only rivers where some of 

 the lakes now are ; Erie and St. Clair being the first to disappeai", 



Mr. A. T. Drummond, I perceive, has been treating of this subject 

 in the Record of Science — and as that periodical has to a certain 

 extent the im^yrimatur of Sir William Dawson, no paper in it should 

 be disregarded. But from Mr. Drummond's special view, I cannot 

 but dissent. He treats the lakes as mere expansions of pre-glacial 

 rivers, and he marks on his map the lines in which those rivei's ran. 

 He makes his principal river run north-east from Duluth. Now 

 that Lake Superior was a gulf and not a mere river is shown by the 

 soundings ; the deep belts are from 25 to 100 miles broad, which 

 precludes the fluvial idea, and they are scarcely in the line he traces. 

 I show a copy of the United States hydrographical map, adding to 

 it Bayfield's soundings, and a smaller shaded map exhibiting graphi- 



<;ally, though imperfectly, the arithmetical facts, the darkest being the 

 deepest pai"t of the lake. Again, the geological strata are newer as 

 ■one proceeds south-westerly ; that was therefore the direction of the 

 earliest currents and iceberg streams. Mr. Drummond notes that Lake 

 Superior is on an axis of depression, but he does not seem to recog- 

 nize that this axis is not in the line of his valley as marked, but on 

 the contrary runs from east to west, far to the southward of his line 

 nor does he consider the lateness of the synclinal folding — which 



