478 NEW YORK STATE MUSEUM 



Cirques^ and grooves. Glacial cirques are found in at least three 

 instances within this region. One of these is on the southern slope 

 of Cat mountain, near the northern boundary. This cirque contains 

 a small pond which is not on the map. A second is on the southern 

 slope of Skiff mountain [pi. 8, fig. 2] and also contains a pond. The 

 third is on the southwestern slope of Mount Steven; this one does 

 not contain a lake. 



On the northern shore of Paradox lake is a large glacial groove, 

 displaying a smoothly polished surface [pi. 9, fig. i and 2]. 



Striae are rare. Those found have already been recorded. 



Boulders are common, some of considerable size. These boulders 

 are off all kinds of Adirondack rocks, Potsdam sandstone being 

 very common. 



PART 3 



General geology 



The crystalline rocks of the Adirondacks are part of the great 

 series forming the Laurentides of Canada. It has never been 

 doubted that these crystalline rocks are of Prepotsdam age. 



The Potsdam sandstone lies almost undisturbed upon their eroded 

 surfaces, and in Prepotsdam time the Precambric sediments had 

 been tremendously folded and faulted and intruded at great depths 

 by at least onie series of plutonics. They had then been uplifted and 

 worn down many thousands of feet until only the cores remained, 

 and until their surfaces had attained a topography of" only moderate 

 relief. This surface had then sunk beneath the advancing Potsdam 

 sea. 



Distribution and character of formations. The crystalline com- 

 plex consists in part of sedimentary rocks, lithologically identical 

 with the Grenville series of Canada ; in part of intrusives, which 

 resemble the Norian series of Canada, and in part of other intrusives 

 being of different character. 



*A cirque is an amphitheater with precipitous or very steep sides Avhich is 

 excavated by a glacier at its upper portion. The ice cracks off and carries 

 away the rock from the mountain until by eating backward it leaves these 

 precipitous walls surrounding the valley on all sides except its outlet. Cirques 

 often contain small lakes. 



