644 PHYSIOGRAPHY 



area is being inscribed perhaps in several different ways. The surface 

 of the earth, like an ancient manuscript, is frequently written upon 

 in different directions; and with different characters. It is the duty 

 of the physiographer to translate this ancient palimpsest, and deduce 

 from it the history of the development of the features of the earth's 

 surface. It has been said that "geology is the geography of the past," 

 but to the physiographer this formula has a yet deeper meaning. 

 There is a physiography of the past, of venerable antiquity, which 

 has begun to receive attention. Ancient land surfaces, buried during 

 geological eras beneath terranes which were deposited upon them, 

 have here and there been exposed once more to the light of the sun, 

 owing to the removal by erosion of their protecting coverings. In 

 northern Michigan, for example, one may gaze on the veritable 

 hills and valleys which were fashioned by the wind, rain, and streams 

 of pre-Potsdam days of sunshine and shower. These fossil landscapes 

 invite special study, not only on account of their poetic suggestive- 

 ness, but as furnishing evidence, supplementary to that afforded 

 by organic records, ripple-marks, shrinkage-cracks, etc., as to the 

 oneness of nature's processes throughout eons of time. The consider- 

 ation of past physiographic conditions, the tracing of former geo- 

 graphic cycles, the study of the concurrent development of primary 

 and secondary physiographic features, the causes and effects of past 

 climatic changes, and the influences of these and still other events 

 of former ages on the present expression of the face of nature, offer 

 not only a fascinating, but a far extended field for research. 



One especially important development of the study of past physio- 

 graphic conditions, and the manner in which they merge with the 

 present phase of the same history, is the connection between the life 

 of the earth and its control by physical environment. The present 

 and past distribution of floras and faunas affords important data 

 supplementary to those recorded by abandoned stream-channels, 

 glacier-scorings, elevated and depressed shore-lines, desiccated lake- 

 basins, and other physical evidences of former geographic changes. 



In the excursions into the domain of the unknown, here suggested, 

 the physiographer seeks the companionship and counsel of both the 

 geologist and the biologist. 



Physiography and Life 



In the study of the relation between physiography and the present 

 state of development of living organisms on the earth, it is convenient 

 and logical to recognize two great subdivisions: the one, the control 

 exerted by physiographic features on the distribution of plants and 

 animals; and the other, the reaction of life on its physical environ- 

 ment, and the modification in the relief of the lithosphere and the 



