ESSENTIAL FEATURES OF THE GEOGRAPHICAL CYCLE 595 



different form-elements of a given structural mass are at each stage of its 

 physiographic evolution systematically related to one another, were not 

 then recognized. The terminology by which these ideas are set forth 

 is a subordinate matter, although it is of course desirable that some 

 one reasonably consistent terminology should be generally adopted as 

 ii matter of convenience. But it is today inevitable that the fundamental 

 ideas of the reasonableness of land forms and the systematic relations 

 of their elements should be accepted and made use of in their description. 

 The reasonableness is not exhibited only in the sequence of forms and 

 the systematic relations of their elements during the uninterrupted 

 progress of a single cycle ; it is also exhibited, although in a more complex 

 manner, when one cycle is interrupted at any stage of its progress by a 

 movement which introduces another cycle; or by a volcanic or climatic 

 accident which for a time disturbs its ordinary progress. Great practical 

 advantage follows from the recognition and utilization of these ideas, 

 for they serve to impress, first, the helpful physiographic principle that 

 every structural mass has, at any stage of its erosional development, 

 a reasonable surface form; and, second., the equally helpful principle 

 that if a structural mass is moved at any time, the form that it had 

 gained when the movement took place must always be specified, as well 

 as the new attitude into which it was placed by the movement and the 

 changes it has suffered since the movement — always provided that the 

 changes since the movement have not wholly obliterated the pre-move- 

 ment forms; in that case, whatever importance the movement may have 

 in a geological study, geographical study is not responsible for it. 



Induction and Deduction tn the Scheme of the Cycle 



A frequent misconception of the scheme of the cycle is one that regards 

 it as based chiefly on deduction. It is true that various expositions of 

 the scheme have been cast in a deductive form, because that is the most 

 convenient form in which to present a general idea to mature readers; 

 and it is also true that, as in all geological and physiographic reasoning, 

 deduction frequently either anticipates observation or fills in gaps where 

 observation is lacking; but to imagine that the scheme as a whole is 

 deductive, in the sense of being contrived independent of observation 

 and induction, is absurd. Its different phases are all composite results 

 of seeing and thinking, and of thinking and seeing; and it would be 

 impossible today to state in just what proportion these two comple- 

 mentary processes have contributed to the total results. As a matter 

 of fact, even the penultimate stage of a normal cycle of erosion first 



