86 The American Geologist. February, i89!i 
The origin of the lakes is perfectly apparent: they are the re- 
sult of the damming up of old lines of drainage by glacial detritus. 
The amount of material deposited by the ice sheet is very small 
as compared with the heavy masses found in other parts of the 
state, in this elevated region the soil being always thin or entirely 
wanting. However, the topograph}^, high, steep ridges separated 
by narrow valleys, is such that a comparativelj' small amount of 
drift has been enough to materiall}' interfere with the drainage, 
and thus form the lakes. As a matter of fact, the lakes are the 
best indication of glacial action to be seen in this region ; for the 
character of the rocks is such that they have not preserved 
scorings, transported boulders cannot be distinguished from the 
countrj^ rock, and sections of glacial deposits are very few. The 
only clear indication of ice invasion, besides the lakes, is the 
common occurence of roches moutonnees. 
Wilmurtlake. five miles northwest of Morehouseville, Hamilton 
county, furnishes an instance where the filling has but slightly 
changed the original outlines. It is about one and one-half 
miles long and one-fourth as wide, with gently sloping shores of 
sandy till covered with soft, spongy forest soil. That these 
shores are original and in no degree the result of deposition from 
the lake at a higher level, is perfectly clear from their contour 
and from the character of the materials composing them. A few 
rods back from the lake the east and west banks become steep ; 
particularly the former, where there is a considerable cliff, and 
an elevation of four to five hundred feet above the lake within 
half a mile. The north and south banks, on the other hand, are 
rather flat; the former rising a little and then dropping rapidly; 
while through the latter is afforded an eas}- outlet for the waters 
of the lake. The preglacial valley in which the lake lies is thus 
clearly defined; and it is evident that the water of the lake is 
derived from a very limited area. The visible inlets are but four 
in number, all ver}' small, most of the water reaching the lake by 
soaking through the spong}- soil. From this fact it follows that , 
ver}^ little sediment is brought in; hence the slight change of 
outline, which is limited to the shores adjacent to the mouths of 
the inlets. Of course, sediment is distributed to a greater or less 
extent over the whole lake bottom, but this does not affect the 
surface outline. A large flat island near the western shore, 
appears, at first glance, to be a result of sedimentation; but closer 
