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THE POPULAR SCIENCE MONTHLY. 



Oliio upon the unusual rise of any of its upper tributaries. At 

 Pittsburg thousands of coal barges collect during low water to 

 take advantage of these waves of translation, and move forward 

 upon them with their valuable freight like a vast army to supply 

 the great cities of the Mississippi Valley with fuel. But, as with 



Fig. 1. jAt~l'EK ( 'oNULii.MEKATE BoWLDEK, TllRKE FeKI IN DlAMETKK, IKuM iS'oKTH OF 



Lake Huron. Found near Union, Boone County, Ky. (See Map II.) From photograph 

 by the author, reproduced in The Ice Age of North America, p. 328. 



everything else, the best gifts of Nature are those which come in 

 moderation. Enough is better than more. Excessiv e floods inter- 

 fere with navigation as effectually as does a lack of water. 



With these facts in mind, while surveying, in the year 1882, 

 the glacial boundary across the Mississippi Valley, I reached Cin- 

 cinnati, having traced the border line to the river twenty-five or 

 thirty miles above the city. Upon crossing to the general level of 

 the hills in Kentucky, I found various indubitable evidences that 

 the ice had extended across the trough of the Ohio, and left its 

 marks several miles south of the river over the northern part of 

 Boone County, and up to an elevation of more than five hundred 

 feet above low-water mark. This was along the watershed be- 

 tween the Licking and Ohio Rivers, which was continuous at this 

 height to the central part of Kentucky. Among other evidences 

 one of the most conspicuous was a bowlder of jasj^er conglom- 

 erate, three feet in diameter, found near Union, in Boone County, 

 which was subsequently transported to Chicago as a part of the 

 Ohio glacial exhibit at the Columbian Exposition. Its right to 

 have a place in an Ohio exhibit was due partly to the fact that it 

 was discovered by an Ohio man, but chiefly from the fact that, at 



