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THE POPULAR SCIENCE MONTHLY.

Ohio 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

PSM V45 D202 Jasper conglomerate boulder from north of lake huron.jpg

Fig. 1.—Jasper Conglomerate Bowlder, Three Feet in Diameter from North 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. Excessive floods interfere 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 Cincinnati, 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 between 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 jasper conglomerate, 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