I 



MAIN MORAINIC SYSTEM OF THE SCIOTO LOBE. 391 



No indication of an attenuated sheet of drift was noted south of this outer 

 member. In the middle member of the morainic system, near the line of 

 the Pittsburg, Fort Wayne and Chicago Railway and between the villages 

 of Lakeville and Shreve, the morainic knolls are somewhat larger, but 

 none exceeding 40 feet in height were observed. A few basins occur 

 among the knolls. The northern member is well exhibited a few miles 

 north of this i-ailway, in the vicinity of Springville, and thence westward to 

 Lake Fork. The several members become combined near Lake Fork, and 

 it is probable that for a few miles west from that stream the middle member 

 has overriden the outer, for the knolls south, southeast, and west from 

 Loudonville have a size and sharpness somewhat greater than the outer 

 member usually displays, their height being often 30 feet or more, and that, 

 too, at altitudes fully 1,100 feet above tide. Some basins occur among the 

 knolls where closely aggregated. These features are more common on the 

 middle than on the outer member. 



In the valley of Lake Fork there is a terrace standing at the glacial 

 boiindary about 100 feet above the creek. At Grreersville, 4 miles south of 

 the glacial boundary, it has a height of only 75 feet, and at Gann, 4 miles 

 farther south, its height is not more than 60 feet. Upon following up Lake 

 Fork from the glacial boundary one soon finds knolls at an altitude lower 

 than the ten-ace. For several miles the high terrace appears at intervals 

 along the border of the valley, while in the midst of the valley, at consider- 

 ably lower levels, there is a knob-and-basin topography. The basins cover 

 several acres and the centers are depressed 10 to 15 feet or more below 

 their rims. Their bottoms are peaty and marshy, and therefore presumably 

 filled to some depth. They are surrounded by knolls of various sizes, form, 

 and trend, while near them at the border of the valley are level-topped 

 gravel deposits standing 50 feet or more above the general level of the 

 morainic tracts in the valley. Phenomena somewhat similar to these are 

 displayed in several valleys in northwestern Pennsylvania just above the 

 glacial boundary, and may be common in other parts of the glaciated 

 district. Their cause is not well understood, but it is thought that they 

 are probably due to the lingering of an ice mass in the central portion 

 of the valley after a jjassage for the escape of water from beneath the ice 

 had been opened along the borders of the valleys. The ice sheet may 

 have been broken up and the terraces formed around its detached masses, 



