1902.1 DAVIS — SYSTEMATIC GEOGRAPHY. 1 251 



may be led to think that he sees things that do not exist. There is 

 certainly some danger of this kind, but it can be greatly lessened 

 by good training — without which the explanatory method is indeed 

 valueless — and in compensation for the little danger that remains, 

 there is the great increase in the thoroughness and accuracy of ob- 

 servation that results from bringing forward the various idealized 

 types to be confronted with the facts in the field. If doubt finally 

 remains, it may be expressed by the phrase, "as if" : — The Sus- 

 quehanna valley looks as if it were in the stage of narrow flood- 

 plain scrolls. The initiated reader is thus concisely put in posses- 

 sion of the most probable conclusion as well as of the doubt that 

 accompanies it. As a matter of practical experience, it may be 

 urged that the gain from attempted explanation far outweighs its 

 danger ; and in illustration of this conclusion reference may be 

 made to the curious case of the Connedogwinet, a branch of the 

 main Susquehanna opposite Harrisburg. The branch has an un- 

 usually serpentine course, and the tangents between its curves are 

 of extraordinary length. On visiting it in the spring of 1901, I 

 expected that it would show normal nanow flood-plain scrolls ; but as 

 a matter of fact, its scrolls were found to be distinctly abnormal, in- 

 asmuch as they are nearly all on the down-valley side of the tan- 

 gents. Truly, this is not a matter of great geographical conse- 

 quence ; the farmers would cultivate the scrolls, on whichever side 

 of the tangents they might lie ; but it is certainly of some physio- 

 graphical interest to note their abnormal position, because it con- 

 tradicts a generalization that is well supported by the repeated oc- 

 currence of examples in various parts of the world ; a generalization 

 that is fully explained by simple processes, perfectly accordant with 

 the laws of stream flow. No explanation of the abnormal situation 

 of the Connedogwinet scrolls has yet been suggested ; indeed, as 

 far as I have read, no mention of them as abnormal features has 

 ever been made. Their peculiar arrangement seems never to have 

 been noticed until it was brought out as an exception to the rule of 

 flood-plain development. This example may therefore be taken to 

 show that, far from there being serious danger of seeing imaginary 

 facts by the light of theoretical explanation, a well defined con- 

 ception of ideal types is a positive aid in correct observation. 



16. Framework of Physiographic Classification. — If the explana- 

 tory method of physiographical description were adopted, it would 

 result in the construction of a mental framework on which all 



