GLACIAL POTHOLE 



17 



lU'forc (MittM-in.^ tlu' MustMiin one notices tlie " Bnicli Mark" established 

 1)\ the U. S. (JeoloKiijil Survey in 1911 on which is inscTihed 

 tlie latitude and longitude, 40° 46' 47.17" X., 73° 58' 41" W., 

 and heii^ht al)()\e s(M level, S() feet. 



On the right is a "pothole" from Russell, St. Lawrence Co., N. Y., 

 formed by an eddy in the waters of a stream beneath the 

 melting ice of the glacier that covered Northern New York. 

 The stream carried pebbles that, whirled around by the 

 eddy, cut and ground this hole, which is two feet across and four feet deep. 

 On the left is a large slab of fossiliferous limestone from Kelleys Island 

 in Lake Erie near Sandusk}^ whose surface has been smoothed , 

 grooved and scratched by the stones and sand in the bottom 

 of the vast moving ice sheet or glacier that covered the 

 northeastern part of North America during the Glacial Epoch. The front 

 of this continental glacier is now thought by most geologists to have re- 

 treated northward across Lake Erie from 30,000 to 50,000 years ago. At 

 Kelleys Island the ice was moving from east to west. 



Bench Mark 



Glacial 

 Pothole 



Glacial 

 Grooves 



AT THE ENTRANCE TO THE MUSEUM 



