332 AUTHORS' ABSTRACTS 



oxidation. Weathering, on the other hand, destroyed both of these 

 minerals and effected much oxidation. The first process could hardly 

 be regarded as destructive, the last is eminently so. 



The weathered dike occurs in the nearly vertical rock wall of the 

 creek gorge, which is doubtless of postglacial origin. As the dike, in 

 its present condition, would offer almost no resistance to the attack of 

 the stream, it is evident that in the first stages of gorge cutting the 

 rock must have been nearly or quite unweathered. From this it fol- 

 lows that the weathering, as now seen, has been accomplished in post- 

 glacial time. 



