96 
the rapids have not yet reached the very headwaters and those which hap- 
pen to be preserved just as they were upon the sink-hole plain. 
The drainage was confined to the surface, since the streams and the 
water table were very pear the general surface level. After this condition 
had been thoroughly established the whole region was uplifted without con- 
siderubie tilting, to an elevation somewhat above that which it now pos- 
sesses, an elevation amounting to upwards of 200 feet. Following this the 
ig. 15. View looking northwest from side of monadnock shown in Fig. 15. 
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 litdle. As a result the streams flow at a level 
somewhat above the rock floors of their valleys. Other minor incidents oc- 
curred which have left their impress upon the region but which need not 
be discussed here. After the first elevation took place, rapids passed up 
the main streams cutting gorges in the vaileys. 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 
