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NEW YORK STATE MUSEUM 



in both form and relation. They lack concentric parallelism, in 

 other words are not in regular series ; and they are not always 

 transverse or normal to the line of motion of the tool, as shown 

 by the band of crushing or gouging. Figure 14 shows these 

 characters. 



To summarize: the gouge 

 or dragging fractures would 

 seem to be the effect of a 

 steady dragging motion of a 

 boulder with large contact sur- 

 face, while the chatters are the 

 product of unsteady, percus- 

 sive or pounding movement of 

 points of boulders or small 

 contact surfaces. 



Limestone flutings. Over 

 'large districts in the southern 

 part of the limestone area the 



Fig. 14 Gouge fractures j£& sur f ace j s worn j nto ser } eS 



of parallel, cylindrical ridges of several feet diameter, separated by 

 equally regular troughs or hollows. These features which can be 

 attributed only to ice erosion are illustrated in plates 60-63. As the 

 amount of erosion and the direction of the ribs and ice movement 

 are inconsistent with the work of the latest ice sheet the discussion 

 of the topic is deferred to the next chapter. 



Prewisconsin glaciation 



Theoretic considerations. In the preceding pages several 

 features have been mentioned as difficult of explanation or incon- 

 sistent with the conception of a single ice invasion. The facts 

 and argument favoring the view of multiple glaciation will be 

 summarized here. 



If the generally accepted conclusions of glacialists, that the north- 

 eastern states have been repeatedly glaciated since Tertiary time, 

 are well founded, it is quite impossible to except or exclude 

 New York from all ice invasions earlier than the latest, or Wis- 

 consin. The several glacial epochs recognized in the Mississippi 

 valley have been named on page 137. The very old drift of New 

 Jersey and southeastern Pennsylvania is believed to be as old, cer- 

 tainly, as the Kansan, and probably represents the ' Preaf tonian, 

 which is now sometimes called the Jerseyan when referring to the 



