1 68 POPULAR SCIENCE MONTHLY. 



early school days, somewhat enlarged by a more mature variety of ad- 

 jectives, is usually the stock of words with which the explorer tries to 

 reproduce the features of the landscapes that he crosses, and as a result 

 his descriptions are often unintelligible; the region has to be explored 

 again before it can become known to those who do not see it. The 

 longitudinal relief of certain well-dissected coastal plains, or the half- 

 buried ranges of certain interior aggraded basins, may be taken as 

 examples of forms which are easily brought home and familiarized by 

 explanation, but which commonly remain remote and unknown under 

 empirical description. 



It may be urged that in many geological discussions from which 

 geography has taken profit, consideration is given to form-producing 

 processes rather than to the forms produced. This was natural enough 

 while the subject was in the hands of geologists; but geographers 

 should take heed that they do not preserve the geological habit. The 

 past history of land forms and the action upon them of various pro- 

 cesses by which existing forms have been developed, are pertinent to 

 geography only in so far as they aid the observation and description of 

 the forms of to-day. 



Further illustration of the growing recognition of form as the chief 

 object of the physiographic study of the lands is seen in the use of the 

 term, 'geomorphology/ by some American writers; but more important 

 than the term is the principle which underlies it. This is the accept- 

 ance of theorizing as an essential part of investigation in geography, 

 just as in other sciences. All explanation involves theorizing. When 

 theory is taken piecemeal and applied only to elementary problems, 

 such as the origin of deltas, it does not excite unfavorable comment 

 among geographers. But when the explanation of more complicated 

 features is attempted, and when a comprehensive scheme of classifica- 

 tion and treatment, in which theorizing is fully and frankly recognized, 

 is evolved for all land forms, then the conservatives recoil, as if so bold 

 a proposition would set them adrift on the dangerous sea of unre- 

 strained imagination. They forget that the harbor of explanation can 

 only be reached by crossing the seas of theory. They are willing to 

 cruise, like the early navigators, the empirical explorers, only close 

 along shore; not venturing to trust themselves out of sight of the land 

 of existing fact; but they have not learned to embark upon the open 

 ocean of investigation, trusting to the compass of logical deduction and 

 the rudder of critical judgment to lead them to the desired haven of 

 understanding of facts of the past. 



One of the bolder explorers of the high seas of theory is Powell, 

 who defined in the term 'baselevel' an idea that had long been more 

 or less consciously present in the minds of geologists, and which has 

 been since then of the greatest service to physiographers. Powell and 



