936 



SCIENCE 



[N". S. Vol. XXXI. No. 1 



Imagine, for a moment, that the observer 

 had no mental conception corresponding 

 to what is commonly understood by the 

 word, hill. He would then have to fall 

 back on geometrical terms, such as apex, 

 slope, base, and so on, in order to give an 

 account of a hill when he sees one ; and his 

 account would involve awlnvardly long 

 paraphrases. Or imagine that when the 

 observer writes down the term, hill, the 

 reader conceives the form that we usually 

 mean by the term, hollow. The reader 

 might mentally conceive a very definite 

 landscape ; but it would have little relation 

 to the landscape that the observer had 

 seen. 



CONTRASTS OF EMPIRICAL AND EXPLANA- 

 TORY METHODS 



Let me contrast somewhat further the 

 empirical and the rational use of type 

 forms. In so far as ideal forms of types, 

 with their corresponding terms, are learned 

 partly from direct observation, partly 

 from books and maps and pictures, they 

 may be treated either empirically or 

 rationally. If treated empirically, each 

 type, form, however learned by the stu- 

 dent, must have been derived from some 

 one's observational experience, without ex- 

 planatory interpretation. If treated in 

 the explanatory fashion, all the members 

 of the series that are based on induction 

 should be rationally or genetically ac- 

 counted for as far as possible ; while many 

 other members, developed by deduction, 

 will be perfectly understood, even though 

 they are purely imaginary. Under the 

 empirical method, diagrams are unsafe if 

 they depart from the forms of nature, for 

 their departures can hardly be reasonable 

 under a method from Avhich reason is ex- 

 cluded. In support of this strong state- 

 ment, one need only turn to those fanciful 

 not to say fantastic landscapes, which have 



so often defaced the pages of empirical 

 text-books, and which bring together in the 

 most absurd manner all sorts of incon- 

 gruous land forms. Under the rational 

 method, diagrams and especially block- 

 diagrams, of which more will be said be- 

 low, are of immense service; they present 

 the graphic equivalent of deduced forms, 

 whereby another person than the deducer 

 may easily apprehend the intended mean- 

 ing; and they serve at the same time as 

 graphic definitions of a systematic termin- 

 ology. 



Furthermore, each member of the em- 

 pirical series has to be learned without con- 

 sideration of its origin and without expla- 

 nation of its relation to other forms. 

 Hence to the geographer who employs the 

 empirical series, the corresponding actual 

 forms in a landscape will seem to stand in 

 purely arbitrary association with one 

 another; the occurrence of one element of 

 form can not be logically taken to indicate 

 the associated occurrence of another ele- 

 ment; the use of empirical types in the 

 description of actual landscapes or regions 

 requires that every part must be described 

 for itself. On the other hand, all the 

 types in an explanatory series, and par- 

 ticularly the deduced types, are learned 

 in view of their origin by the action of 

 some reasonable process on some specified 

 structure through some limited period of 

 time ; and hence type-forms of this kind 

 are necessarily considered in relation to 

 their natural associates. The association 

 may be regional, as in the ease of the differ- 

 ent parts of an ideal landscape produced 

 by the imaginary action of process on 

 structure to a given stage of development; 

 or the association may be sequential, as in 

 the case of a single element of form fol- 

 lowed in imagination along its successive 

 stages of erosional change, from the ini- 

 tial, through the sequential to the ultimate. 



