216 W. H. SHERZER 
localities. The relation of the striz to the rock-basin seen in 
Figs. 6 and 7 shows that the adjoining rock surface was but 
little lowered by the early Wisconsin. In the Lake Erie region 
the pre-Wisconsin gouges on flat surfaces were not obliterated 
by both Wisconsin sheets. So far as our rock topography in 
this region is due to ice action this was accomplished by the 
first movement, that of the Illinoian. Judging from what is 
known concerning the rock topography of the Great Lakes 
region, the writer ventures to suggest as a ‘‘working hypothesis” 
that the real axes of all the major troughs and rock basins 
throughout this wide area point approximately to the Lauren- 
tide center of ice accumulation and that they were produced by 
the earliest of the four general movements. 
W. H. SHERZER. 
MICHIGAN STATE NORMAL COLLEGE, 
Ypsilanti, January 30, 1902. 
