154 GEOLOGY OF OHIO. 



think, be at least partially read. In the chapter on Surface Geology, 

 Vol. II., this subject is more fully treated, and I will only say here in 

 passing, that these deeply-cut valleys constitute a marked feature in the 

 topography, not only of Ohio, but of several of the Middle and Eastern 

 States. They were undoubtedly formed when the continent stood at a 

 higher level than now ; as, in some instances, they reach below the pres- 

 ent surface of the ocean. They were certainly excavated, and by streams 

 which, for thousands of years, flowed through them with rapid currents 

 on their way from the highlands of the ancient continent to the sea level. 

 A subsequent depression of the land filled these valleys with water, 

 arrested the flow of the stream, and caused the deposition in their old 

 channels of the material transported by their currents. In this way they 

 were more or less perfectly filled, and sometimes obliterated. At a still 

 Liter period the continent was elevated to its present level ; the lines of 

 drainage were again established, and in some instances the accumulation 

 of drifted material in the old valleys was partially cut away, leaving 

 here and there terraces to mark the ancient level of the flood plain. Of 

 these terraces, the one to which I have referred, south of Massillon, is a 

 good example. In some cases, however, the old valleys were completely 

 filled, and the draining streams following the line of lowest levels were 

 turned into some new trough, so that now the old, deserted river-bed ex- 

 ists as a deeply excavated trough, filled to the brim with sand and gravel. 

 Such channels are not often discovered, except when borings are made 

 for oil or coal. Through these means we have now come to know some- 

 thing of a great number of them. As I have mentioned in the report of 

 the geology of Summit county, we have evidence that at one time the 

 waters of Lake Erie stood several hundred feet higher than now. This 

 is proved by the lake ridges which mark the old shore lines at different, 

 periods in the descent of the water-level, and also by a series of accu- 

 rately stratified clays which once filled the valley of the Cuyahoga 

 nearly to the summit level. When the water stood highest in the Lake 

 it is evident that the line of drainage by the Niagara was not open, and 

 that the surplus water flowed into the Ohio by several outlets or waste- 

 weirs. Of these there seems to have been one which connected the val- 

 leys of the Cuyahoga and Tuscarawas. Through this waste-weir a flood 

 poured across Stark county, and brought down the materials which now 

 fill the old valleys, as well as those which compose the gravel beds that 

 occupy much of the central part of the county. An examination of these 

 gravel beds will show that they are composed partly of well-rounded 

 fragments of the adjacent rocks — usually the sandstones and limstones of 

 the Coal Measures— partly of pebbles and bowlders of crystalline rock 



