642 PHYSIOGRAPHY 



account for the origin of mountains of the Appalachian type, I have 

 been able to find but one mention of the role played by the transfer 

 of matter from deep within the earth outward, and in part its extru- 

 sion at the surface, in causing folds in the crust from beneath which 

 it was derived. Problems of fundamental importance are outlined 

 by the considerations under review. 



To the immediate question, What is the best plan for enlarging 

 our knowledge of the physiography of volcanoes? the reply seems 

 pertinent: Press on with the study of both active and dormant or 

 extinct examples. In this connection it should be remembered that, 

 while the individual volcanoes and volcanic mountains which have 

 been critically studied can be enumerated on the fingers of one's 

 hands, those which are practically unknown number many thou- 

 sands. The fact that Mont Pelee and La Soufriere of St. Vincent 

 during their recent periods of activity furnished examples of at least 

 two important phases of volcanic eruptions not previously recognized 

 is an assurance of rich returns when other eruptions are critically 

 investigated. 



While it is difficult to formulate the precise questions, so numerous 

 are they, to be asked of volcanoes, whether active, dormant, or dead, 

 and in various stages of decay and dissolution, it is plain that all 

 the facts that can be learned concerning them should be classified and 

 put on record, and their more obvious bearings on the fundamental 

 questions concerning the condition of the earth's interior, and the 

 changes there taking place, pointed out. In this connection-- and 

 as is true in all branches of research the fact may be recalled that 

 energy expended in discovering, classifying, and recording facts 

 decreases the time and force necessary for the framing of multiple 

 hypotheses. With an abundance of well-classified and pertinent 

 observations in hand, the nature of the thread on which the gems 

 of truth should be strung usually declares itself. 



Resume. On a previous page of this essay the desirability was 

 suggested of recognizing ideal types with the aid of which the multi- 

 tudinous surface features of the earth could be classified and studied. 

 Thus far we have considered the elements in the relief of the earth's 

 surface which have resulted from changes within its mass. We term 

 them primary physiographic features, because their birth precedes 

 the modifications of the lithosphere due to agencies acting externally. 

 They are (1) the topographic forms resulting from contraction on 

 account of cooling, or of condensation owing to growth in mass; (2) 

 the surface changes produced by intrusions of magmas into the 

 earth's outer shell; and (3) the results of volcanic eruption. Among 

 the more important idealized models in our future physiographic 

 museum there should be displayed continental platforms, oceanic 



