432 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



In the upper 2 or 3 feet there are ordinarily not more than one-fourth as 

 many pebbles as there are 5 or 6 feet below the surface. This is ti'ue in 

 the immediate vicinity of the Scioto. At higher levels, near the border of 

 the basin, pebbles are not so scarce. On the contrary, surface bowlders are 

 numerous near the border, while in the central portion they seem to be 

 covered, in places at least, by the clay just mentioned. Orton called the 

 writer's attention to several exposures in the city of Columbus where 

 bowlders abound at a depth of 4 or 5 feet beneath the silty clay. This 

 peculiar distribution of bowlders has not been observed outside the city 

 of Columbus, either by Professor Orton or the writer, but may be widely 

 develoiDed in the silt-covered portion of the basin, no special search for the 

 bowlders having been made. 



The gravel belts along streams are most conspicuous on the Scioto and 

 Olentangy rivers. Darby Creek, and the lower course of Big Walnut (from 

 the latitude of Columbus southward). The gravel along' the Scioto is in 

 places capped by a few feet of till which seems to indicate that its deposi- 

 tion occurred before the final retreat of the ice from this region and opposes 

 the view that it was an outwash from the Powell moraine. The belt on the 

 Scioto is narrow above Columbus, but is well defined all along the brow of 

 the bluffs of the rock gorge extending back 100 to 200 yards on either side 

 of the rock bluffs. Below Columbus the rock bluffs disappear and the 

 gravel belt has a width of a mile or more. Its eastern border is followed 

 nearly by the canal all the way from Columbus to Circleville. The west 

 border lies back from the river at varying distances from a few yards up to 

 nearly a mile and, in the vicinity of Circleville, is, as noted above, 2 or 3 

 miles from the river. On Olentangy River the gravelly belt is one-half 

 mile or more in breadth. Possibly it marks the line of discharge for the 

 main glacial stream leading down from the Powell moraine north of 

 Columbus, though it seems quite as probable that its deposition preceded 

 the formation of that moraine. 



On Darby Creek the gravel in the lower part is confined to the valley 

 of the stream, but in the upper part above Plain City considerable gravel 

 is found in the plains bordering the valley. This gravel is perhaps an out- 

 wash from the Powell moraine, which lies north of that part of the creek. 

 South from Plain City the bluffs wherever examined contain till. In the 

 valley in Pickaway County, are terraces which may be of glacial age, 



