F;TREA>rs OF giants' KETTLES AX[) ESKERS C•()^n'AIM•:D V^ 



and hills and esker ridges during the wane of an ice-sheet, were .sur[)ris- 

 ingly rapid, in comparison with tlie generally very slow rates of geologic 

 action. Watch the artificial processes of granite and niarhle al)rasion 

 and polishing, and there will be no need to doubt that the largest rock 

 kettle of the Interstate park, of Archbald, Christiania, or lAicerne could 

 be hollowed out during the warm months of even a single year by a 

 stream 20 or 50 feet wide, and 2, 3, or 5 feet deep, falling down a moulin 

 200 or 500 feet deep, and well sup[)lied at the bottom with grinding 

 boulders of granite and other very hard rocks. Crevasses and moulins 

 would be formed in successive years at nearly the same situation, thus 

 producing such a profusely kettled surface as in the Interstate park or 

 the Glacier garden. 



Although we have been able to cite many localities of giants' kettles 

 due to moulins and their waterfalls, they are far exceeded in numl)ers by 

 the gravel and sand deposits called kames and eskers, which are attrib- 

 utable mostl}'' to larger glacial streams. From my observation, it seems 

 clearly within the limits of truth to estimate that we have records of 

 hundreds of kaine and esker streams for every one that is known to 

 have formed a giants' kettle by plunging down a moulin or by flowing 

 in any cascade or rapid along its subglacial passage. 



If the retreat of the ice-fields under ablation was so rapid as a tenth 

 of a mile yearly, which was apparently its rate near Stockholm, accord- 

 ing to observations by De Geer, or about half a mile each year during 

 centuries, as was probably true of the area of the glacial lake Agassiz 

 and the vast plains of the Saskatchewan and Winnipeg countr}'-, we can 

 not doubt that the most massive esker ridges, as in Sweden, or in Maine, 

 and the highest kame hills, as the Devil's Heart hill, 175 feet high, in 

 North Dakota, could be formed within a few years for any single section, 

 or perhaps even within one summer for the great kame mentioned. 

 Some of these gravel-depositing rivers, as shown by the widths of esker 

 ridges and plateaus, were two to five or ten times larger than those of 

 the moulins and rock kettles. 



The streams flowing in the summers from the border of the ice-sheet 

 were doubtless of larger size and greater numbers during the final dis- 

 appearance of the ice, when they formed the kames and eskers, than at 

 any previous stage of the Glacial period. Many of the giants' kettles, 

 if not all, are clearly referable to an early or intermediate stage. For 

 example, they are found in Maine and in Scandinavia on coastal tracts 

 that were depressed and submerged beneath the sea to the depths of 

 hundreds of feet when the ice was finally melted away, as is demon- 

 strated by the relations of the glacial drift and the overlying marine 

 deposits, which contain molluscan shells such as now exist only in the 



