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ISRAEL C. RUSSELL 



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 Michi- 

 gan, for example, one may gaze on the veritable hills and valleys 

 which were fashioned by the wind, rain, and streams of pre-Potsdam 

 clays of sunshine and shower. These fossil landscapes invite special 

 study, not only on account of their poetic suggestiveness, but as fur- 

 nishing 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 consideration of past physi- 

 ographic conditions, the tracing of former geographic cycles, the study 

 of the concurrent development of primary and secondary physi- 

 ographic 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 fascinat- 

 ing, 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 hfe 

 of tlie 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 



