GLACIAL SUCCESSION IN OHIO. 141 



lin observed decisive evidences of the lapse of a considerable 

 interval between the formation of a moraine lying east of Mad 

 river, near Urbana and Springfield, and the moraines on either 

 side of it, the moraine on the east being one of the later Scioto 

 moraines, while that on the west is a Miami moraine. This older 

 moraine proves to be the outer moraine of the Miami lobe (see 

 map). While this moraine was being formed the Miami lobe 

 occupied the Mad river drainage area, and the waters from the 

 melting ice-lobe were forced toward the south into the Little 

 Miami valley, passing just east of Springfield. The course is 

 well defined, there being a gravel plain leading south along the 

 east side of this moraine. The altitude of this gravel plain is 

 much greater than that of the immediate bluffs of Mad river val- 

 ley, but is lower than the water-shed between the Mad river and 

 the Scioto river system, just east of it. It consequently presents 

 somewhat the appearance of a broad irrigating ditch, following 

 the face of a slope at a considerable altitude above the stream. 

 When the ice had retreated from the Mad river basin the drain- 

 age of the high country to the east of Mad river soon opened 

 channels directly across this gravel plain and the moraine west 

 of it down to the trough in which the river flows. Similar chan- 

 nels were formed by streams leading down to Mad river from 

 the elevated country west of its basin, and a broad valley was 

 opened along the axis of the trough. When a fresh advance of 

 ice occurred the Miami lobe came nearly down to the Mad river 

 valley from the west and covered the upper portion of the west- 

 ern tributaries. Its moraine, in crossing the interglacial valleys, 

 descends into them, but only partially fills some of them, thus 

 repeating the phenomena of the outer moraine, in the White- 

 water valley, as noted above. Similarl}^ the Scioto lobe tres- 

 passed on some of the eastern tributaries of Mad river, and its 

 moraine partially fills the interglacial valleys. It should, per- 

 haps, be stated that these interglacial valleys do not follow pre- 

 glacial troughs, but instead, have bluffs standing as high as the 

 interfluvial portions of the slopes of the basin. Their excavation 

 began with the retreat of the ice-sheet from the outer Miami 



