PHYSICAL GEOGRAPHY IN THE UNIVERSITY. 85 



souri,^ and the north branch of the Susquehanna in Pennsylvania ; 

 the Seine in northwestern France, and the Moselle in western 

 Germany, may be cited in illustration of this kind of occurrence. 



Another case in which a second adolescence is unlike the 

 first is found in regions of tilted structure, where the strata are 

 of diverse resistance, thus giving good opportunity for the devel- 

 opment of subsequent streams. In the beginning of the first 

 cycle there are no subsequent streams. All the drainage is con- 

 structional (antecedent streams not being now considered). In 

 adolescence, the drainage is chiefly consequent, although subse- 

 quent side streams are then beginning to bud forth from the 

 consequent streams. In past-mature stages, the subsequent 

 streams may have acquired a considerable part of the drainage 

 area. Now, if a region of this kind, with consequent and subse- 

 quent drainage, is bodily elevated, all the streams are revived ; 

 they all cut down new trenches toward the new baselevel. 

 But in this case the revived subsequent streams begin the new 

 work at the same time as the revived consequent streams, and 

 they will go on rapidly in acquiring still more drainage area. 

 Therefore, in the adolescence or maturity of the second cycle, 

 the drainage area acquired by the subsequent streams will be 

 proportionately large ; much larger than at the same stage of the 

 first cycle. Much faith maybe placed in this deduction. If the 

 drainage of an adolescent region is largely subsequent, and but 

 little consequent, the region may be regarded as almost certainly 

 in a second cycle of development, after a first cycle of well- 

 advanced age. 



Illustrative material. — One of the greatest difficulties in the 

 way of teaching physical geography arises from the failure of 

 the student to know what the teacher is talking about. The 

 teacher may have traveled and observed extensively ; a large 

 variety of geographical forms are in his memory, ready to be 

 summoned by name when picturing the stages of the deductive 



'It has been suggested to me by Mr. Arthur Winslow that the Osage has increased 

 its original meanders in cutting down its gorge. The other rivers here mentioned 

 seem to have done the same thing. 



