351 THE SOUTHERN 8H0KES OF LA.KE SUPERIOB. 



shore the beaches are of large angular stones, and sand is hardly to 

 be seen except at the mouths of rivers. The rivers of the southern 

 shore are often silted up, and almost invariably, it it said, barred 

 across by sand spits, so that they run sometimes for miles parallel 

 to the lake, and separated from it only by narrow strips of sand project- 

 ing from the west." In these remarks it will be seen that the writer 

 speaks only in part from personal observation, though his observations 

 receive confirmation from the detailed survey by Messrs. Foster and 

 Whitney of the chief features of the southern shore. 



The alteration in the relative levels of land and water, which is so 

 strikingly recorded on the exposed face of the rocky coast, also finds 

 its record in the less marked features of the river beds ; and a dis- 

 covery of copper relics, already brought under the notice of the 

 Institute,* made during the past year near the mouth of the Carp 

 River, some two miles to the south of Marquette, also disclosed 

 evidence of an ancient river bed, situated about ten feet above the 

 level of its present channel. On this subject Professor Agassiz, after 

 describing the terraces, which form a striking feature of the lake shore, 

 remarks :f " We must consider also, the river terraces which present 

 similar phenomena along their banks all around the lake, with 

 the difference that they slope gradually along the water courses, 

 otherwise resembling in their composition the lake terraces, 

 alltogether composed of remodelled glacial drifts, which, from the 

 influence of the water and their having been rolled on the shores, 

 have lost, more or less, their scratches and polished appearance, and 

 have assumed the dead smoothness of water pebbles. Such terraces 

 occur frequently between the islands, or cover low necks connecting 

 promontories with the main land, thus showing on a small scale, how, 

 by the accumulation of loose materials, isolated islands may be com- 

 bined to form larger ones, and how, in the course of time, by the same 

 process, islands may be connected with the main land. 



The lake shores present another series of interesting phenomena, 

 especially near the mouth of larger rivers emptying into the lake over 

 flats, where parallel walls of loose materials, driven by the action of 

 the lake against the mouth of the river, have successively stopped its 

 course and caused it to wind its way between the repeated accumula- 

 tion of such obstacles. The lower course of the Michipicotin River 

 is for several miles dammed up in that way, by concentric walls across 

 which the river has cut its bed, and, winding between them, has 



* Ante, page 235- 



t " Lake Superior, its Physical Character," 4c., p:vs$»s 414, and 41." 



