THE METAMORPHISM OF GLACIAL DEPOSITS 487 
this jointed condition of till in central and northern Ohio, and in 
New York along creeks tributary to the outlet of Keuka Lake.* 
3. The altered drift described in this paper contains abundant 
carbonates, probably deposited from circulating eround water, 
whereas carbonates are either absent or less conspicuous in the 
superjacent drift of later origin. ‘This difference between the two 
drifts is apparent even when tests are made near their contact; the 
observation holds for exposures studied in all the areas under con- 
sideration. 
4. The color in the case of the drift above described, its indurated 
condition, and the jointing appear to be associated with the change 
or metamorphism which develops tillite from glacial drift. 
5. I believe that so far as the regions considered in this paper are 
concerned two Pleistocene epochs are indicated by a contact of the 
bluish and yellow till. 
t Journal of Geology, Vol. XV (1907), pp- 583, 584- 
