PHYSIOGRAPHIC PROBLEMS OF TODAY 533 



becomes of fundamental importance to the physiographer. Since 

 extinction of species among physiographic features has probably not 

 occurred, and connected series of forms which grade one into another 

 confront us, the practical lesson taught by the success of schemes of 

 biological classification seems to be that ideal physiographic types 

 should be chosen correlative with species among plants and animals. 



By "ideal physiographic types" is meant complete synthetic 

 examples of topographic and other physiographic forms, which will 

 serve the role of well-defined species in the study of the surface features 

 of the earth. Ideal types may be likened to composite photographs. 

 They should combine critical studies of many actual forms, within a 

 chosen range, and in addition be ideally perfect representatives of the 

 results reached by specific agencies operating under the most favorable 

 conditions. Like the idealized personalities of history and religions, 

 the types of physiographic forms might well be more perfect than any 

 actual example. When such idealized types shall have been chosen 

 after careful study, described with care, and illustrated by means of 

 diagrams, maps, pictures, models, etc., a comparison with them 

 of actual examples on any portion of the earth for the purpose of 

 identification and classification would be practicable. A well- 

 arranged catalogue of ideal types would be an analytical table of 

 contents to the history of the evolution of the features of the earth's 

 surface, and constitute a scheme of physiographic classification. 



In illustration of what is meant by an idealized physiographic 

 type: We find in nature a great variety of alluvial deposits, now 

 designated as alluvial cones or alluvial fans. They present a wide 

 range and infinite gradations in size, shape, composition, structure, 

 angle of slope, degree of completeness, stage of growth or decadence, 

 etc. Complications also arise because of the association and inter- 

 growth of such alluvial deposits with other topographic forms. In 

 constructing the ideal type the characteristics of many of the most 

 perfect actual alluvial cones, aided by a study of the essential features 

 of similar artificial structures, should be combined in an ideally 

 perfect and representative example which would serve as the type of 

 its specie. All actual examples might be compared with such a type, 

 their specific and generic relations determined, and their individual 

 variations noted. In like manner, other topographic forms, ranging 



