INNER BORDER OF THE SCIOTO LOBE. 433 



standing 20 or 30 feet above the stream, and occupying- in places nearly 

 the whole width of the valley. These terraces may perhaps have suffered 

 some reduction from their original level. If not they indicate that less 

 excavation has taken place since they were formed than took place between 

 the withdrawal of the ice from the border plain and the deposition of the 

 gravel. 



On Big Walnut Creek till is present above the latitude of Columbus, 

 but from that latitude southward there seems to be but little within a mile 

 or more east from the creek, the drift being gravelly. For a few miles 

 above the mouth of Black Lick, an eastei'n tributary, the interval between 

 the two creeks, 1 to 2 miles in width, is occupied by a gravel plain which 

 stands 20 to 30 feet above Big Walnut Creek. The belt is narrower below 

 the mouth of Black Lick, but continues to the Scioto. Bowlders were 

 observed on the surface of the broad portion of this plain, about 2 miles 

 above the mouth of Black Lick, which are either at the surface or embedded 

 a foot or two in a brown clay that caps the gravel. This clay is seldom 

 more than 3 or 4 feet thick, and usually but 12 to 18 inches. 



In Madison County there are belts of land slightly depressed below 

 bordering till plains that are said to be underlain by gravel. They are 

 known as "glade," and the timber on them differs from that on the border- 

 ing till tracts, being nearly all white oak without underbrush, while the 

 bordering tracts have a variety of timber and much underbrush. The 

 gravel of these glades is probably of glacial age, but the mode of deposition 

 and points of connection with the ice margin have not been worked out. 



The following represent the principal well sections obtained in which 

 the drift has notable thickness. 



At Westerville the gas well passed through 94 feet of drift. 



The boring for gas at Plain City penetrated 119 feet of drift. This 

 boring has about 10 feet of gravel and sand at surface, the remainder of the 

 drift being mainl}^ blue till. The well mouth stands 15 feet below the level 

 of the railway station, or 919 feet above tide. 



At Columbus the statehouse well, siuik in 1857-1860, penetrates 123 

 feet of clay, sand, and gravel.^ The gas well made on the banks of the 

 Olentangy River in 1886 penetrated 104 feet of diift.^ The altitude of the 

 well mouth is 737 feet above tide. At J. M. Linton's, near the Scioto, 2 



'Geology of Ohio, Vol. I, 1873, p. 113. ^Ibid., Vol. VI, 1888, pp. 281-282. 



MON XLI 28 



