406 LAKE SUPERIOR. 



bergs of the present period at least, are insufficient to account 

 for them, as they are limited to a narrower zone. And to bring 

 icebergs in any way within the extent which would answer for 

 the extent of the distribution of erratics, we must assume that 

 the northern ice fields, from which these icebergs could be detach- 

 ed and float southwards, were much larger at the time they pro- 

 duced such extensive phenomena than they are now. That is to 

 say, we must assume an ice period ; and if we look into the circum- 

 stances we shall find that this ice period, to answer to the phenome- 

 na, should be nothing less than an extensive cap of ice upon both 

 poles This is the very theory which I advocate ; and unless the 

 advocates of an iceberg theory go to that length in their premises, I 

 venture to say, without fear of contradiction, that they will find the 

 source of their icebergs fall short of the requisite conditions which 

 they must assume, upon due consideration, to account for the whole 

 phenomena as they have really been observed. 



But without discussing any farther the theoretical views of the 

 question, let me describe more minutely the facts as observed on the 

 northern shores of Lake Superior. The polished surfaces, as such, 

 are even, undulating, and terminate always above the rough lee-side 

 turned to the south, unless upon gentle declivities, where the polish- 

 ed surfaces extend in unbroken continuity upon the southern surfaces 

 of the hills, as well as upon their northern slopes. On their eastern 

 and western flanks, shallow valleys running east and west are as 

 uniformly polished as those which run north and south ; and this fact 

 is more and more evident, wherever scratches and furrows are also 

 well preserved and distinctly seen, and by their bearings we can 

 ascertain most minutely, the direction of the onward movement which 

 produced the whole phenomena. Nothing is more striking in this 

 respect than the valleys or depressions of the soil running east and 

 west, where we see the scratches crossing such undulations at right 

 angles, descending along the southern gentle slope of a hill, travers- 

 ing the flat bottom below, and rising again up the next hill south, in 

 unbroken continuity. Examples of the kind can be seen everywhere 

 in those narrow inlets, with shallow waters intersecting the innumera- 

 ble highlands along the northern shores of Lake Superior, where the 

 scratches and furrows can be traced under water from one shore to 



