^;^2 The American Geologist. •^""^' iQoi- 
most violent and frequent winds of our northern climate ; con- 
sequently and because of the absence of bed-rock its develop- 
ment has been quite rapid. When wave erosion first began to 
cut into the drumlins, sea cliffs were formed on all sides of 
the drumlin islands and traces of these cliffs still exist, in some 
cases with large trees growing thereon. 
As a result of their more exposed position, however, the 
northern ends were cut back most rapidly and then began the 
growth of the connecting beaches. The waves loosened from 
the drumlins more material than they could grind up and this 
material began to travel along shore, moved by the diagonally 
approaching waves, now in one direction, now in the other, but 
always gaining in the direction away from the most frequent 
winds. Slowly beach-bars grew out from each end of the sea- 
cliff's on the northern end of the drumlins, and these joined 
with those of the neighboring drumlins, tying them together 
and producing a continuous coast line. 
On the drumlins where wave erosion is most rapid, nearlv 
vertical cliffs are formed and the stiff drumlin till exposed to 
the combined action of weathering and erosion assumes the 
most fantastic forms. Buttress-like projections stand out from 
the cliff face, their upper edges reduced by rain erosion to 
sharp, thin, knife-like edges. Between these buttresses are 
ditch-like depressions down which streams of mud flow during 
wet weather. On such of the drumlins as are tree-covered 
there is a continual down-sliding of undermined trees and the 
farmers of this region, well knowing how rapidly their land 
is disappearing, place only temporary' fences along the cliff 
edges. The very steepness of the cliff's of boulder clay shows 
how rapid this wearing back must be. 
As the drumlin cliffs are cut back by wave erosion, the 
beaches are constantly changing their form and moving shore- 
ward. From the data obtained from the farmers who note the 
necessary moving of fences and the shrinking of their fields, I 
have estimated that the cuts are moving backward from a few 
inches to ten feet a year where cutting is most rapid. Since 
the retreat of both the sea cliffs and beaches depends upon the 
rapidity with which the waves grind up and carry away the 
material loosened from the drumlins it is interesting to note 
the following fact which indicates, in a way, how rapid this 
jirocess is. 
