W. J. Miller— Ice Movement and Erosion. 295 



a steep slope rising three hundred feet above the Precambrians. 

 The formations outcropping on this slope are shown in, the sec- 

 tion. Resting upon the Precambrians are several feet of weak 

 sandstones which are followed by the sandy limestones of the 

 Pamelia; then come the hard Lowville and Black river lime- 

 stones, followed by weak lower Trenton shales and limestones ; 

 while the summit is capped by the hard, crystalline Trenton 

 limestones. The streams passing over this slope are character- 

 ized by gorges with waterfalls and rapids. From the summit 

 of this slope and extending for several miles westward is a well 

 defined terrace developed upon the limestone. 



Rising from the western side of the above-named terrace 

 there is a second slope higher and much steeper than the first. 

 The rise is commonly about 450 feet within a third of a mile. 

 The soft Utica shales outcrop at the base of this slope and 

 they are followed by the Lorraine shales with an upward 

 increasing sandstone content. The summit of this terrace, 

 known as Tug Hill, is more irregular and stream-dissected 

 than the limestone terrace below. A]l streams flowing across 

 the steep slope of this terrace have high gradients and have cut 

 deep narrow gorges locally called " gulfs." A third terrace, 

 much less well-defined, is formed by the Oswego sandstone 

 capping. The much higher gradients of the eastward flowing 

 streams from Tug Hill and the much steeper slope and greater 

 height of the eastern front of Tug Hill^ as compared to other 

 parts of the district, all argue for a recent and considerable 

 cutting back (westward) of the Paleozoics here. 



At first these terraces, in their present form, were thought 

 to have been due entirely to water action, but an examination 

 of the region shows that some other explanation must be 

 sought. The steep fronts of the terraces are certainly young 

 topographic features, which precludes the possibility of their 

 having been formed during the long preglacial period of 

 erosion in this ancient region. On the other hand, Black river 

 has done very little work of erosion, between Lyon Falls and 

 Lowville, in postglacial times, as proved by the fact that the 

 stream has not yet cut its way through the alluvium and 

 reworked drift filling the valley bottom, and also because 

 glacial striae and kames near the river level have not been dis- 

 turbed. Thus also the slight trench cut into the Precambrians 

 along here could not have been postglacial in origin. 



There is still the possibility that glacial waters might have 

 developed the terraces, but the writer has looked in vain for 

 evidence of any such vigorous water action, especially along 

 the higher part of the limestone terrace where records would 

 surely be left. Even if a large stream had flowed along the 

 ice edge and under the steep front of Tug Hill, its gradient 



