302 W. J. McGee—Superposition of Glacial Drift. 
. 
removed by the glacier. 
an 
a ; 
contains a greater number of erratics ; and many silicified Ni- 
studied the formation at many 8 es that these clays Ltn 
| 1 to 4 feet. 
_ 2. Clays of the Hamilton shales, about ___..---- 50 feet. 
the Rockford shales. For the relations of the forma 
a description of some of its fossils, see Prof. S. Calvin’s papers x ‘ih 
Journal, vol. xv, p. 460, and in Bull. Geol. and Geog. Surv. Terr., vol. 1, 
va 
