Twenhofel— Granite Bowlders. 135 



Furthermore, it can hardly be close at hand; but must 

 lie to the westward beneath the cover of higher beds. 



The new facts slightly strengthen the hypothesis that 

 the bowlders reached their present position from floating 

 ice. If so carried, their place of origin is as uncertain 

 as before. It may be that Powers is correct and that 

 they were derived from close by; but if so, ice is the 

 only agent that could have carried them. Perhaps they 

 came from the northwest — northern Kansas or southern 

 Nebraska, where the buried granite ridge rises highest; 

 but again floating ice must be called upon to bring about 

 the transportation, and such a source indicates that large 

 accumulations were possible at no great distance above 

 sea-level, which in turn indicates a very cold climate for 

 Kansas during the deposition of the Weston (LeEoy) 

 shales. Until, however, granite like that of the Rose 

 bowlders has been found by the drill at a stratigraphic 

 elevation equivalent to that of the "Weston shales (strati- 

 graphic horizon is not meant), such a source must be 

 considered fully as hypothetical as any other. 



University of Wisconsin, 

 Madison, Wis. 



