ICE WORK IN SOUTHEASTERN MICHIGAN 213 
westerly. At most of these localities the late Wisconsin are the 
most abundant, although the early Wisconsin are well repre- 
sented, testifying to the more energetic nature of the latter 
sheet. The amount of range in the direction of the striz of the 
two Wisconsin series is very notably less in this region than to 
the west and north. This is to be explained by the fact that we 
are here nearer the axis of the Huron-Erie lobe, along which’ 
the movement was theoretically only slightly divergent. 
Central portion.—The only satisfactory exposure of striz 
upon the central ridge of the county is found at the Woolmith 
quarries, in the north central part of the county, between May- 
bee and Scofield, upon the Detroit & Lima Northern Railroad. 
The strie of the two Wisconsin glaciations are well preserved 
about the main quarry, but those of the earlier series are more 
conspicuous. Thirteen readings give an average of S. 34.1° W., 
ic Mae TAM MenOte2 7 Sku22°5. Wie tows) 40.5 1 WV) dhe, late 
Wisconsin series is alone found in the small Hoffman quarry 
to the south. From both quarries twenty-two readings were 
taken and found to average N. 65.7° W., with a range of 40° 
(CONEIo TciuWestowN 51652 Wale tis tof imterest atomnote that 
here, upon the Macon and at the Sibley quarry, some distance 
out from the main axis of movement, when a considerable num- 
ber of observations were made, the range is from 40 to 50°, or 
about 25°.on either side of the mean. It is not probable that 
doubling or trebling the number of readings would much alter 
the amount of this range. This amount of divergence is due to 
the fact that the ice moves out continually at right angles to 
the margin of the lobe, as pointed out some years ago by 
Chamberlin.* | In the case of such a lobe as the Huron-Erie of 
the late Wisconsin ice, with its main line of movement toward 
the southwest, at any point some distance to the north of this 
central axis the strize would have a more northerly course when 
the lobe was small and be deflected more and more to the west 
as the lobe increased in size. Theoretically the striz on the 
northward side of the mean direction of movement should indi- 
t Seventh Ann. Rept. U. S. Geol. Surv., 1888, p. 201. 
