

PLATE 12 



Pebbles and stones carved by sand blast. 



Fig, 1. Sand-blasted glacial pebble (glyptolith), from the surface of a wind-blown tract. 

 Fig. 2. Sand-blasted glacial erratic (glypolith) of the three-edged type, from cliffs, north side 

 of Nantucket. The under side shows glacial striation unaffected by subsequent wear. 



