242 DAVIS — SYSTEMATIC GEOGRAPHY. [AprUS, 



these successive paleogeographies, just as the slow depression of the 

 Netherlands, the eruptions of Vesuvius and Pelee, the washing of 

 neglected fields, and the migrations of Europeans into the open 

 lands of America constitute elements of the geography of to-day. 



The science of geography is therefore, like all other sciences, 

 concerned with the relationships of things which, when they enter 

 into relationships of other kinds, belong under other sciences, and 

 which are known to be pertinent to geography not by their own 

 qualities but by the relationship in which they are considered. It 

 is the classification of the elements of a subject thus constituted 

 that we have to consider. 



It is not my purpose however to present here a detailed statement 

 of a classification, but rather to set forth the nature of a classification 

 which might, when expanded in a more technical geographical 

 publication, afford suitable categories for all kinds of geographical 

 facts. It will suffice therefore to indicate briefly the larger divisions 

 of the subject, and to pursue only one of these divisions, namely 

 the lands, into details. 



6. Subdivisions of Physiography. — Geography as a whole has 

 already been shown to consist of two chief divisions, physiography 

 and ontography. Pliysiography has four chief subdivisions — the 

 earth as a globe, the atmosphere, the oceans and the lands. Let 

 us set aside for the present all but the last subdivision. The lands 

 should first be treated as a whole, and their contrast with the other 

 exterior parts of the earth considered. A notable contrast, of great 

 significance in its ontographical relations, is found between the 

 lands covered by the atmosphere, and the sea floors covered by the 

 oceans. The latter are monotonously cold, dark and quiet, as well 

 as remarkably uniform in shape and constitution j while the former 

 exhibit a variety of forms, such as high and low, smooth and rugged, 

 flat and steep, and experience a succession of changing conditions, 

 such as wet and dry, calm and windy, hot and cold. The general 

 weathering and washing of the lands, whereby their waste gees to 

 make the gain of the sea floors, results in their being scored by 

 many branching systems of valleys ; this highly specialized kind of 

 inequality being as significantly characteristic of the land surface 

 as is smoothness of the blanketed sea floors. There is nothing 

 new in all this, but geographers too generally fail to recognize these 

 general features of the lands as the determining physical environ- 



