Geographic Methods in Geologic Investigation. 15 



It is not easy to sketch the history of this awakening. Ram- 

 say years ago contributed an element in his explanation of plains 

 of marine denudation ; Jukes opened the way to an understand- 

 ing of cross valleys ; Newberry excluded fractures from the pro- 

 duction of the most fracture-like of all water ways ; and our 

 government surveyors in the western territories have fully devel- 

 oped the all important idea of base level, of which only a brief 

 and imperfect statement had previously been current. I cannot 

 say how far European geographers and geologists would be will- 

 ing to place the highest value on the last named element ; to me 

 it takes the place of Lesley's ocean flood, in leading off the whole 

 procession of outdoor facts. It is indispensable at every turn. 

 Recently, mention should be made of Lowl, of Prague, who has 

 done so much to explain the development of rivers, and of 

 McGee, who has explicitly shown that we must "read geologic 

 history in erosion as well as in deposition." 



If it be true that the greater part of this second advance is 

 American like the first, it must be ascribed to the natural oppor- 

 tunities allowed us. The topographers of the Appalachians had 

 a field in which one great lesson was repeated over and over 

 again and forced on their attention. The patchwork structure of 

 Europe gave no such wide opportunity. The surveyors of the 

 western territories again found broad regions telling one story, 

 and all so plainly written that he must run far ahead who reads 

 it. It is to this opportunity of rapid discovery and interpretation 

 that Archibald Geikie alludes in the preface to the recent second 

 edition of his charming volume on the " Scenery of Scotland." 

 He says that since the book first appeared he has seen many parts 

 of Europe, " but above all it has been my good fortune to have 

 been able to extend the research into western America, and to 

 have learned more during my months of sojourn there than dur- 

 ing the same number of years in the Old Country." (p. vii.) 



Our position now is, therefore, while structure determines form 

 as our earlier topographers taught, and while form-producing 

 processes are slow, as had been demonstrated by the English 

 geologists, that the sequence of forms assumed by a given struct- 

 iire during its long life of waste is determinate, and that the 

 early or young forms are recognizably different from the mature 

 forms and the old forms. A youn^ plain is smooth. The same 

 region at a latter date will be roughened by the channeling of its 

 larger streams and by the increase in number of side branches, 



