The Old Southward Train. 
499 
catur and in the adjacent townships of Winnebago and Stephen¬ 
son counties, Illinois. A few bowlderets were observed in these 
towns also, but the only bowlder of considerable size found in 
this remote portion of the train was a block of Mud Lake quartz¬ 
ite two feet in diameter, lying on the roadside in section 16, 
Rock Run. 
A wedge shaped area is outlined upon the map lying between 
the margin of this bowlder fan and the border of the driftless 
area. The drift upon this area is very thin except at certain 
points upon its margin and its surface bears the impress of 
erosion topography. Its surface has been diligently ex¬ 
amined for the local quartzite drift, but thus far without result. 
No rock resembling the Waterloo types has been found within 
this area through any of the road and railway exposures that 
have been examined, though in the various crossings and re-cross¬ 
ings of the tract over a hundred miles of travel have been 
made. The drift-line exposed contains Niagara and Devonian 
fossils, and thus bears evidence of its derivation from the lake 
Michigan basin and is unquestionably of more ancient origin 
than that which contains the quartzite fragments. 
The breadth of this belt of bowlder distribution is consider- 
ably greater than in either of the other trains, extending as it 
does across five townships in the adjacent counties of Wisconsin 
and Illinois. Its greater linear extent, however, together with 
the rapid fanning out of the ice lobe which is here assumed to 
have affected its distribution may be considered as satisfactory 
explanations of its extent. 
Hypothesis for its phenomena .—The presence of this drift 
material within the area of the Rock river basin and along the 
extended axis of the Green Bay lobe, is most satisfactorily 
explained to the author by the hypothesis of an extended ice 
tongue down this trough during one of the earlier episodes in 
the glacial history of this region. Upon the accompanying 
map the outlines of such a lobe are indicated by the dotted lines, 
which also include the area of overflow to the southwest, denoted 
by the esker belts with their quartzite contents in the valleys 
south and southwest of Freeport. 
The amount of quartzite drift observed within the distinctive 
