830 THE POPULAR SCIENCE MONTHLY. 



waves was disturbed by the bottom near the edge of the deep water 

 marking the ancient boundary of the lake, sand-bars would be de- 

 posited there as we find them, and these would stretch across the 

 mouths of the submerged river-valleys, and on further uplifting they 

 would separate the waters occupying them from those of the great 

 lake, which, meanwhile, would go on adding more sand to them from 

 without. This is the condition of things existing at present. The 

 changes of level that have brought it about have not been uniform 

 and constant ; they may have consisted of a single sinking and rising, 

 but more probably there were many. Even yet we see that the solid- 

 seeming earth is sinking and swelling there in a most capricious manner. 

 It is hard to tell to what the present movements are tending even 

 whether for a long period the land is to remain substantially at its 

 present level, whether it is to rise until the river-lakes are drained and 

 the Western Michigan lake-ports are left stranded inland, or whether 

 the country is to be again submerged. We see, within the memory of 

 those now living there, a variation of level to the extent of six feet at 

 least, and in both directions. Forty years ago the land seems to have 

 been at a higher level than it is at present, and to have continued so 

 long enough to permit the growth of large trees on land since sub- 

 merged. Then there was a subsidence to an extent of several feet, 

 then an uplift until the waters were below their present level, and at 

 last accounts another subsidence seemed to be in progress. Who can 

 tell us its limits, either as to time of continuance, rapidity, or extent ? 

 What is the nature of this movement ? There are difficulties in the 

 way of accounting for it that would not exist if Lake Michigan were 

 the ocean. A rising and falling of the land as a whole would include 

 the bed of the lake, and would not produce these changes of relative 

 level. To lift the bed of Lake Michigan, might pour out a part of its 

 contents, and so cause an enormous increase in the volume of the St. 

 Clair, Detroit, and St. Lawrence Rivers, with a corresponding diminu- 

 tion when a subsidence was taking place, the rivers rising as the lake 

 was going down, and falling as the waters of the lake were rising ; 

 but this, we believe, has not taken place. Is it a shrinking and swell- 

 ing of the upper strata of Western Michigan, leaving the deeper strata 

 in which the bed of the lake rests comparatively undisturbed ? Is 

 it a rocking of the lake-bed from side to side, one part sinking as 

 another rises ? What is the extent of the country through which these 

 movements are felt ? These questions, and others relating to the mat- 

 ter, would seem to be of interest. Perhaps, if the Government would 

 take the subject in hand and cause a record to be kept of the water- 

 level at all light-houses and life-saving stations, a few years might 

 throw light upon it. 



