INNER BORDER OF THE SCIOTO LOBE. 435 



Near the southwestern border of this plain, in Madison County, the 

 drift probably exceeds 100 feet in average depth. The boring-s for gas at 

 London are the only ones reported that have reached rock. These, as pre- 

 viously noted, have in one case 155 feet of drift, and in another 200 feet. 

 East from the Scioto numerous exposures of rock occur along the main 

 creeks, and some hills, near Lithopolis, rising much above the level of the 

 plain, have rock at surface. This does not, however, prove the absence of 

 valleys with heavy drift deposits; indeed, such valleys probably traverse 

 this district. Orton called attention, as follows, to .evidence that in pre- 

 glacial times the Olentangy Valley was a prominent channel traversing the 

 Scioto Ba.sin:^ 



The levels run in the construction of the Worthington and Dublin turnpike 

 show that low water in the Olentangj^ west of Worthington is 16 feet lower than low 

 water in the Scioto at Dublin. The Scioto exceeds the Olentangy several times in 

 volume, and, other things being equal, its valle}^ should be much deeper. It is also 

 to be noted that the disparity would be still more striking if the actual depths of the 

 vallej's were taken into the account. The Olentangy runs upon drift beds, the shales 

 having been cut out to an unknown but probabh' considerable depth, while the Scioto 

 at the point named has a rocky floor. The contrast between the valleys in width is 

 equally marked. As already stated, the Scioto Valley in the northern half of the 

 county is but a narrow gorge, walled with vertical cliffs. Its bottom lands are of 

 small extent and often there is no interval whatever. The valley of the Olentangy, 

 on the other hand, often attains a width of 2 miles, and is seldom less than half a mile. 



BOWLDER BELTS. 



The impression prevails among the residents on the plains southwest 

 of Columbus that there are bowlder belts some miles in length that traverse 

 the district at angles quite different from the trend of the bordering 

 moraines. One of these is said to pass from the uplands 1^ miles southwest 

 of Darbyville, eastward across Darby Creek and the uplands between that 

 stream and the Scioto, coming to the Scioto nearly opposite the mouth of 

 Little Walnut Creek. The writer has crossed this supposed bowlder belt 

 at several points and endeavored to outline its course and width, but found 

 that it is not sufficiently well defined to admit of ready majDping. In a 

 general way, however, it may be said that bowlders are more numerous 

 along the line designated than on the bordering tracts, though intervals of 

 one-half mile or more occur along the line where bowlders are rare, while 



1 Geology of Ohio, Vol. Ill, pp. 598, 599. 



