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 is v ry 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 



