THE ERRATIC PHENOMENA. 413 



present, the limit between that epoch and the present state of things. 

 Their continuity seems almost demonstrated by the identity of fossil 

 shells found in these stratified deposits, with those now living along 

 the present shores of the same continent, and by the fact that changes 

 in the relative level between sea and main land are still going on in 

 our day. 



Indications of such relative changes between the level of the 

 waters and the land are also observed about Lake Superior. And 

 here they assume a very peculiar character, as the level of the lake 

 itself, in its relation to its shores, is extensively changed. 



All around Lake Superior we observe terraces at different levels ; 

 and these terraces vary in height, from a few feet above the present 

 level of the lake, to several hundred feet above its surface, presenting 

 everywhere undoubted evidence, that they were formed by the 

 waters of the lake itself. 



As everywhere the lake shores are strewed with sand and pebbles 

 stranded within certain limits by the waves, the lowest accumulations 

 of loose materials remain within the action of heavy storms, and 

 within such limit they are entirely deprived of vegetation. 



Next, another set of beaches is observed, consisting generally of 

 coarser materials, forming shelves above the reach of even the severest 

 storms, as shown by the scanty cryptogamous vegetation, and a few 

 small herbaceous plants which have grown upon them. 



Next, other beaches, retreating more and more from the shores, 

 are observed, upon which an older vegetation is traced, consisting of 

 shrubs, small trees, and a larger number of different plants, among 

 which extensive carpets of wonderful lichens sometimes spread over 

 large surfaces of greater extent. And the gentle slope of some of 

 the terraces shows that the lake must have stood at this level for a 

 longer time, as higher banks rise precipitously above them, consisting 

 also of loose materials, which must have been worn out and washed 

 away, for a considerable time, by the action of the waves from the 

 lake. In such a manner, terrace above terrace may be observed, 

 in retreating sheltered bays or along protected shores, over exten- 

 sive tracts ; sometimes two or three in close proximity, perhaps 

 within twenty to fifty feet of each other ; and again, extensive flat 

 shores, spreading above to another abrupt bank, making the former 



