84 IHE JOURNAL OF GEOLOGY. 



The numerical expression of this example would be 20, — , : 

 the minus sign not indicating subtraction, but merely signifying 

 depression ; and the zero indicating that no advance has been 

 yet made in the new cyle. Another model exhibits a broad, 

 gently undulating upland, traversed by a very narrow canyon. 

 This is interpreted to signify that an elevation occurred in the 

 old age of the region, and that since then the streams have simply 

 entered a new youth, incising young valleys in the uplifted 

 peneplain. The formula of this example would be 60, -|-, 3. 

 Examples involving deformation of a land surface, and the 

 accompanying possibility of antecedent streams, are more 

 complicated, and cannot be here introduced. 



It is convenient to use the term, episode, for slight inter- 

 ruptions, so as to express their relative unimportance. I have 

 also attempted the use of the term, chapter, for an unfinished 

 cycle ; but in talking with students this specialization of terms 

 hardly seems necessary. Any region whose surface has been 

 developed, partly with relation to one baselevel, and partly in 

 relation to another ; that is, any form whose development has 

 involved two or more incomplete cycles, is said to have a com- 

 posite topography. Many examples of such forms are encoun- 

 tered. 



Special features of second or later cycles. — It is interesting 

 to notice that, in certain cases, the adolescent stages of a sec- 

 ond or later cycle, following the elevation of a region well 

 advanced in a previous cycle, present features that did not 

 characterize its first adolescence. One case of this kind is seen 

 in meandering river gorges. Young rivers in their first cycle 

 may cut crooked gorges, but they then follow consequent 

 courses, and these cannot manifest the close relation between 

 volume and radius of curvature that is seen in true meanders. 

 This relation is found only in oldish rivers, which develop sys- 

 tematic meanders on their own flood plains. But if the region 

 on which these rivers flow is introduced into a new cycle by 

 uniform elevation, the rivers may cut down their meandering 

 channels and produce meandering gorges. The Osage in Mis- 



