NARRATIVE OF THE EXPEDITION. 215 



that a fluctuation, resembling a tide, has been improperly thought 

 to exist there, and, indeed, similar phenomena appear to in- 

 fluence the Baltic. Philosophers have not been wanting, who 

 have attributed similar appearances to the ocean itself. " It has 

 been asserted," observed Cuvicr, "that the sea is subject to a 

 continual diminution of its level, and proofs of this are said to 

 have been observed in some parts of the shores of the Baltic. 

 Whatever may have been the cause of these appearances, we cer- 

 tainly know that nothing of the kind has been observed upon our 

 coast, and, consequently, that there has been no general lowering 

 of the waters of the ocean. The most ancient seaports still have 

 their quays and other erections, at the same height above the 

 level of the sea, as at their first construction. Certain general 

 movements have been supposed in the sea, from east to west, or 

 in other directions ; but nowhere has any person been able to 

 ascertain their effects with the least degree of precision."* 



On the next day (20th) the wind abated, so as to permit us, at 

 six o'clock A. M,, to issue from our place of detention ; but we 

 soon found the equilibrium of the atmosphere had been too much 

 disturbed to rely on it. At seven o'clock, and again at nine 

 o'clock, we were driven ashore ; but as soon as it slackened we 

 were again upon the lake; it finally settled to a light head wind, 

 against which we urged our way diligently, until eight o'clock 

 in the evening. The point where we encamped was upon that 

 long line of deposit of the erratic block, or boulder stratum, of 

 which the White Rock is one of the largest known pieces. At 

 four o'clock the next morning, we were again in motion, dancing 

 up and down on the blue waves ; but after proceeding six miles 

 the wind drove us from the lake, and we again encamped on the 

 boulder stratum, where we passed the entire day. Nothing is 

 more characteristic of the upper lake geology, than the frequency 

 and abundance of these boulders. The causes which have re- 

 moved them, at old periods, from their parent bed, were doubtless 

 oceanic ; for the area embraced is too extensive to admit of merely 

 local action; but we know of no concentration of oceanic cur- 

 rents, of sufficient force, to bear up these heavy masses, over such 



* Tlieory of the Earth. Modern geologists attribute these changes to the rising 

 or sinkino; of the earth from volcauic forces. 



