Page:Popular Science Monthly Volume 48.djvu/175

Rh The northern tributaries of the Ohio had both these advantages (or disadvantages), and therefore they have the terraces. On the Ohio these are always larger and higher where a tributary comes in from the glaciated region to the north, as, for example, at the mouth of Big Beaver Creek, where the terrace is a hundred and thirty feet above low-water mark. But down the river the supply of gravel diminished, and the terrace becomes correspondingly lower, being at Steubenville and Brilliant only seventy or eighty feet above low water.

I have personally examined every stream emerging from the glaciated area from the Atlantic Ocean to the Mississippi River, and can testify that everywhere substantially the same system of gravel terraces marks them as that which characterizes the Ohio and its tributaries. Without doubt they were formed during the closing stage of the period, when both great torrents of water and vast deposits of glacial débris were periodically released by the melting ice sheet.

So far as direct evidence is concerned in estimating the age of implements in these terraces, it relates to the question whether or not they have been found in undisturbed strata of the original terrace. If they are so found they are as old as the deposition of the gravel which took place in glacial times; for since that period of deposition the action of the present river has been confined to eroding an inner channel, such as is shown in Fig. 3, and to working over the gravel within the limits of its own flood-plain. No disturbances by present floods could affect the gravel of the eighty-foot terrace. That has remained constant from the time of its original deposition.

The direct evidence, therefore, regarding this implement would seem to be as clear and positive as it is possible to be. Relying upon the strength of this, I took the implement to the meeting of the American Association for the Advancement of Science at Springfield, Mass., in August last with great confidence. Nor was this misplaced. On being submitted, at a joint meeting of the Geological and Anthropological Sections, to Prof. F. W. Putnam, Mr. F. H. Gushing, Miss Alice Fletcher, and others, the corroborative indications of its antiquity were readily and emphatically recognized.

Prof. Putnam remarked upon the distinctness with which it retained the patina indicative of the conditions in which it is said to have been found, and said without hesitation that the implement in itself bore evidence of being a relic of great antiquity.

Mr. Gushing remarked that there could be no question that it was a finished implement, and not a "reject"; and that not only had it been finished by careful chipping all along the edge, but it had been finished twice, having been at least once resharpened