CHAP. XIII. ERRATICS OF RECENT PERIOD IN SWEDEN. 239 



birch. Lastly, under the influence of the Gulf Stream, and 

 various changes in the height and extent of land in the arctic 

 circle, a melting of nearly all the permanent ice between 

 latitudes 60° and 70° north, coi-responding to the parallels of 

 the continental ice of Greenland, has occurred, so that we 

 have now to go farther north than lat. 70° before we en- 

 counter any glacier coming down to the sea-coast. Among 

 other signs of the last reti-eat of the extinct glaciers, Kjerulf 

 and other authors describe large transverse moraines left in 

 many of the Norwegian and Swedish glens. 



CJironological Relations of the Human and Glacial Periods 

 in Sweden. 



We may now consider whether any, and what part, of 

 these changes in Scandinavia may have been witnessed by 

 man. In Sweden, in the immediate neighborhood of Upsala, 

 I observed, in 1834, a ridge of stratified sand and gravel, in 

 the midst of which occurs a layer of marl, evidently formed 

 originally at the bottom of the Baltic, by the slow growth of 

 the mussel, cockle, and other marine shells of living species 

 intermixed with some proper to fresh water. The marine 

 shells are all of dwarfish size, like those now inhabiting the 

 brackish waters of the Baltic ; and the marl, in which myriads 

 of them are imbedded, is now raised more than a hundred 

 feet above the level of the Gulf of Bothnia. Upon the top 

 of this ridge (one of those called osars in Sweden) repose 

 several huge erratics, consisting of gneiss for the most part 

 unrounded, from nine to sixteen feet in diameter, and which 

 must have been brought into their present position since the 

 time when the neighboring gulf was already characterized 

 by its peculiar fauna. Here, therefore, we have proof that 

 the transport of erratics continued to take place, not merely 

 when the sea was inhabited by the existing testacea, but 



