414 GEOLOGY OF OHIO. 
Of these varieties, the conglomerates are, perhaps, the most character- 
istic, as they agree quite well with each other in their general composi- 
tion, and differ in a marked degree from the conglomerates otherwheres 
met with in the Drift field of south-western Ohio. 
It seems probable that they may hereafter give the clue to the exact 
location from which they were originally derived. Their peculiarity 
consists in their distinct stratification. Layers of coarse, silicious peb- 
bles are separated from each other by four to eight inches of fine, sandy 
_ quartzite, which 1s very often light green in color, and which sometimes 
has a faint amethystine tint. The conglomerate character is sometimes 
but feebly shown, and then the blocks would be classed as ordinary 
quartzites. The composition of the bowlder belt is best studied in some 
of the newly made stone walls of this district. 
The application of the bowlders to the construction of stone walls 
which provide permanent fencing for the lands on which they are found, 
is one of the most obvious uses to which they can be put, but little has - 
thus far been done in this direction. They have been more largely 
turned to account in the foundations of buildings through the regions 
_ where they are plentiful. The few mechanics that use them skillfully 
are in demand, and bowlder walls are coming to be considered as the 
standard of excellence in the way of masonry. 
These great surface stone quarries of the county are not to be held in 
light esteem. Every farm that lies within the bowlder belt here de- 
scribed has on its surface thousands of perches of the most enduring and 
attractive building rocks of the continent, and it is certain that with 
the increasing age and wealth of the country these supplies will come 
into demand. 
The chief facts in relation to this interesting feature of the Drift for- 
mations of the county have now been given. The bowlders evidently 
belong to the last stage of the Drift period, viz., to the time of northern 
submergence which followed and closed the great ice age. They were 
floated by icebergs across the inland sea that stretched from the Canadian 
Highlands to Central Ohio, but no explanation is proffered of the fact 
that they occur just where they now lie rather than elsewhere. The 
present topography of the country furnishes some suggestions, but no 
adequate explanation of the phenomena is discerned. 
Another of the more unusual phenomena of the Drift is to be noted 
in the obstruction of an old valley by the bowlder clay. This case is 
met with in the bed of a small tributary of Seven Mile Creek, one mile 
west of the village of Camden. The stream has been compelled to 
abandon its old course for a short distance, and to work out a new and 
