INNER BORDER OF THE MIAMI LOBE. 333 



shorter ridge. There are gravel knolls along the Little Miami Valley, near 

 Waynesville, about 5 miles to the east, but the distance from the gravel 

 ridges is so great that it is doubtful if the same stream that formed either of 

 of them also formed the gravel knolls. 



The longer ridge is interrupted near its eastern end by a slight gap (a 

 feature not unusual in eskers). Its greatest height is 30 to 40 feet, while 

 portions are 20 feet or less. Its width, including slopes, is 100 to 200 yards. 

 Its surface is somewhat irregular, as if there had been uneven deposits of 

 englacial drift upon it after the bodj^ of the ridge had been formed. This 

 view finds support in the fact that in Bennett's gravel pit, which opens the 

 ridge to view near its eastern end, there is a change from gravel to till in 

 passing from the center to the north slope of the ridge, the till here being 

 confined to the lower portion of the slope. The exposures are not suffi- 

 cient to show whether or not the till in places reaches the crest of the ridge. 

 Bennett's pit shows great variations in the bedding of the gravel, in dip and 

 thickness, as well as in coarseness of material. The lower part of the pit 

 is more largely gravel than the upper, there being beds of nearly clear 

 sand near the top of the ridge. 



The shorter ridge has a height of 10 to 12 feet and breadth of 50 to 100 

 yards, including slopes. It is opened at Blackford's pit, its cross section 

 being well shown. The surface beds arch over, but the deeper beds are 

 horizontal beneath the center of the ridge. This arching of the surface 

 beds may have been produced in the manner suggested by Russell,^ in his 

 article on the glaciers of the Mount St. Elias region. The view is there 

 expressed that gravel ridges of this class are built up in horizontal beds in 

 tunnels in or beneath the ice sheet, and that upon the disappearance of the 

 ice walls the material next the borders is left unsustained, and therefore 

 settles down, giving the arched appeai-ance to the surface beds. This short 

 ridge has a much smoother surface than the larger one and apparently has 

 no capping of till. At Blackford's pit it is composed mainly of gravel of 

 medium coarseness, there being but little sand and but few cobblestones 

 intermixed. In both ridges the pebbles are composed largely of limestone 

 rocks, not a small percentage being the local rocks. 



Near the mouth of Clear Creek, in Franklin, and for a mile or more 

 southeast from that village, drift knolls are numerous. They range in 



'I. C. Russell: Am. Jour. Sci., March, 1892. 



