Ar(. M[ SciiKi' !• KL, Oiii^^in of Spring Valley Gorge . 163 



not mark a prc-i^lacial draiiiam' line. The dtluT ])i)ssil)k' time 

 periods of oris^in are intcr-i^lacial, ])ost-t;iacial and glacial. 



Intcr-glaclal 'llicorx. 'riic armmnents fur an inler-^lacial 

 theory of origin must l)e similar to those amplified in the sncceed- 

 in,^" ])ara,L;raph. The same ohjeclions also hold. This theor_\- has 

 an even less seenre basis, for admitting- that sneh a stream might 

 be formed inter-glaeially. later giaeial epoehs wonld proliably ol)- 

 litcrate its channel with debris. 



Post-glacial I'hcorlcs. ( )n the sn])position tliat the ( )ld X'alley 

 was formerly tilled high up on its walls with glacial del)ris, it 

 might be conclnded that the Spring Valley drainage formerly pur- 

 sued a conse(juent course superimposed over solid rock, in glacial 

 debris ; soon cutting through this drift into the rock, its course be- 

 came fixed. Then the western portion of the Old A'alley with its 

 greater depth of glacial rubbish, permitting more ra])id cutting 

 than did the rock bound Spring \ alley, has been given its present 

 topography as hitherto dcscril^ed, leaving Spring Valley following 

 •laterally on the east valley wall. This theory is hardly tenable 

 since a mature transverse valley is rarely so completely buried 

 that its topography is not a factor in post-glacial time. The drift 

 would tend to slope downward to the axis of the original valley, 

 and drainage lines originated on the drift-covered valley wall 

 would normally tend toward this axis, rather than cut a channel 

 through solid rock i)arallel to it. 



One theory for the origin of rock gorges in Licking C'ounty 

 is that they have been formed by the undermining of the rock 

 by springs, the action being accelerated by the caving in of the 

 rock roof from time to time.' Such an explanation does not ade- 

 quately account for the great depth (big. 1) and the width of 

 Spring Valley gorge, especially considered with reference to its 

 appearance of newness as elsewhere described. Neither does it 

 account for the large number of granite howdders found along this 

 valley, which must, according to such an explanation, have come 

 from an area above but little larger than that of the present val- 

 ley. The eastern slope of the old valley does not carry many 

 bowlders. This theory, moreover, would demand that the lower 



1 M. 0. Keart. "Licldns County." Gi-olouioil Survey of Ohio. Vol. IIT, I'art 1, 

 (187S), pp. 350, 331. 



