Bowlder Trains of the Latest Glacial Movement. 489 
e. The demonstration of identity in composition and micro¬ 
scopic structure, in both ledge and bowlder train specimens. 
/. The recognition in the distribution of the drift material 
of all the characteristic features of glacial distribution, namely, 
association with all the different members of the glacial forma¬ 
tion, evidences of the effects of glacial transportation and its 
distribution in well defined trains whose locations were deter¬ 
mined by the positions of the ledge exposures and the directions 
of ice movement across their surfaces. 
The convergence of these lines of evidence has afforded the 
author the strongest grounds for the conclusion that no appre¬ 
ciable part of the material hereafter described as belonging to 
the various bowlder trains had its origin in any hitherto con¬ 
cealed or undiscovered ledges in the Waterloo area or in any 
other ledge area near or distant from the locality here described. 
The study of the drift distribution from these ledges has devel¬ 
oped the fact that we have represented within the area of the 
bowlder fan not alone the distinctive trains of bowlders from 
each ledge area, but successive trains from the several areas 
which represent distinct episodes of glacial movement, widely 
differentiated in time, direction of movement and conditions of 
drift dispersion. These are here taken up in the order of their 
prominence as drift phenomena, which is naturally the reverse 
order of their deposition. 
THE BOWLDER TRAINS OF THE LATEST GLACIAL MOVEMENT. 
PLATE XIII. 
Outlines of bowlder fan .—This is embraced entirely within 
the Green Bay loop of the Kettle moraine and its attendant 
overwash deposits and gravel trains. The ledge area lying well 
toward the end of the lobe of which the moraine is the margin, 
and almost in the center of its peripheral arc, was in a posi¬ 
tion to receive the most characteristic effects of attrition and 
dispersion. Hence the striking features of glacial abrasion 
alluded to in the preceding section. Where the line of strike 
coincides with the direction of drift movement, the surface of 
the larger ledges is left in long gentle swells like the fluted 
