96 



the rapids hiwe not yet reached the very headwaters aud those which hap- 

 pen to be preserved just as they were upon the sink-hole plain. 



The drainage ^^"as confined to the surface, since the streams and the 

 water table v^-ere very near the general surface level. After this condition 

 had been thoroughly established the whole region was uplifted without con- 

 siderable tilting, to an elevation somewhat above that which it now pos- 

 sesses, an elevation amounting to upwards of 200 feet. Following this the 



Fig. 1-3. View looking northwest from side of monaclno;li shown in Fig. 13. 

 Closed sink in middle ground. Beyond is the plain of Indian Creek valley. Present 

 drainage subterranean. The remnant of a monadnock (catoctin) interrupts the even 

 sky line just at the right of the center of the background. 



larger streams etched their channels to temporary base level, but soon 

 afterward the region sank a little. As a result the stieams flow at a level 

 somewhat above the rock floors of their valleys. Other minor incidents oc- 

 curred which have k-ft their imju'ess upon tlie region but wliich need not 

 iia discussed herr. .Vfter the first elevation tool; place, rapids passed up 

 the main streams cutting gorges in tlie valleys. As these rapids passed 

 the mouths of the tributaries the latter were left out of adjustment with 

 the master streams and reached them by rushing over high rapids and 



