REVIEW OF GEOLOGICAL STRUCTURE. 4h 
surfaces, presenting a billowy outline to the eye, and frequently holding 
lakelets in the depressions which separate them. The Kames of Ohio, 
are generally of this kind, although some of them are elongated ridges. 
They occupy, however, here, a topographical position which makes it 
‘impossible that they should ever have been the beds of rivers, for they 
form a belt along the summit of the divide between the lake-basin and 
the Ohio Valley, all the way across the State. Their altitude is from 
400 to 600 feet above the lake, z. ¢., 1,000 to 1,200 feet above the ocean> 
and some of them rise nearly 100 feet above their bases. They are com- 
posed of gravel and sand, sometimes horizontally. stratified, more 
generally as interlocking wedges. They contain but few large bowlders, 
and the gravel of which they are composed is well rounded; it is derived 
from both indigenous and exotic rocks. The Bowlder clay is usually ab- 
sent where the Kames are found, and they rest on the underlying rock ; 
but they are occasionally seen to spread over the Till, and are evidently 
of more recent date. — 
In the notice of the Kames given in Chapter XXX, it was suggested 
that they may have been formed by the action of shore-waves, when the 
lake-basin was filled to the brim and they were islands or shoals. This 
view 18 not sustained by any conclusive evidence, but was offered as a 
possible and even probable explanation of a problem of difficult solution. 
That they are not moraines, properly speaking, is certain, as they have 
not the form, composition, nor structure of moraines. They occupy the 
summit of the water-shed, and in their stratification and the rounding 
of their pebbles, distinctly show water action; therefore, although com- 
posed of material which may be morainic, it has been all rolled and re- 
assorted. The pebbles and bowlders contained in the Kames, are such 
as are found in the bowlder-clay, but rounded and worn so that scratches 
and angles have been removed. Everything indicates that they are 
composed of the coarser material of the Till, triturated and rounded by 
water, which washed out the clay. 
Professor Geikie, in the second edition of his “Great Ice Age,” page 
469, suggests that the Kames of the summit of our water-shed are formed 
by sub-glacial rivers and the great quantity of water pouring from the 
glacier when it filled the lake-basin. This is an explanation that would 
satisfy some of the conditions of the problem, but, unless we imagine 
the glacier to have remained for a very long period precisely at this 
stage, it is difficult to see why the washing effect of the water draining 
from it should be so localized. It will be remembered that this belt of 
Kames, along the highlands; divides two areas of Bowlder clay, where no 
gravel-beds, just like these, are found. In the lake-basin there is nothing 
at all like them, and in southern Ohio, the only hills of gravel which 
