wer 
103 
lapse and the return to surface drainage. Briefly, it may be stated that 
the cycle is: surface drainage, partial subterranean drainage, and a re- 
turn to surface drainage. The final state is peneplanation or base leveling. 
5. In youth and maturity nearly all the sinks are solution sinks. 
G6. In old age many of the sinks are formed by collapse. Solution 
sinks may finally be transformed into sinks ef collapse. 
7. Surface streams resting on a plain of soluble rocks with streams 
at lower levels bordering them may have their waters diverted by subter- 
“anean capture. 
8. Piracy probably takes’ place between subterranean streams and 
between parts of the same stream. 
Bloomington, Indiana. 
’ 
References to the “carly pleistocene”’ peneplain in this paper should read “late 
tertiary (?),” since the eyele was interrupted at about the close of the tertiary or 
beginning of the pleistocene period. 
