'.WU 



l..\ Mii.ldx r..ik i<\' Sil\cr Cicck, Siidi pirary will (•(iiiliiiiic nnlil a lialariccd 

 (•(imlitidii of Ihc liradifiils (.f llic Iwo stn-ani syslciiis is rcaclu'd. Sii.li a 

 (•oiiditioii will iiiarU the li(>.t:iiiiiiiiKs of old aiic of tlic strciim systems, when 

 str(>aiii adJusdiKMits ai'c i>rac(ically coiiiiilctc. It is furtlicr noted tliat in 

 the adjiistineiil of the ha ihed trihiilaries to liie icvcfsed draiiiaire. an 

 iiliusiial set of he(hi-ocl< lerraces is iieiiiti' made w liere the ha fhed trihii 

 taiies Join the main stream. 'I'liese tenaces are due to ceiiditions unlike 

 any which have elsewhere come under tiie ohsei'val ion of the writer. 



The special features in this pajier t(. which the atleidion of physio.iira- 

 phers is directed are as follows: delinition of the terms ■•^ceolo-.Mc struc- 

 luro" iiiid "topo.ijniphic condition" as physio.iiraiiliic terms; a ^roiiiiiir^' of 

 the pliysiojiraphic factors tui(h'r two heads, active factors and coniliti<jiiin,ti 

 factors: a division of the conditioiiin.ir factors into the so-called "material" 

 and "time oloments". with definitions and illustrations of the new terms 

 used: a declaration of the impiutance of y;eolojcic structure (litholoi^y and 

 structure I in the dexcloiiment of re,i:ional toi)o.i,M-aphic foi-ms in the staj^es 

 of youth and maturity:'' an extension of the use ui' the term "I'ejuvenation" 

 in which the term "static rejuvenation" is proiiosed, and alon.a; with the 

 terni a retiional examiile of it offered. These are phases of physiography 

 which the writer attempts to make pertinent or which he wishes to present 

 initiiilly. Finally contriluitions to re.uional physioiiraphy are made in the 

 treatment of a particular re,i;ion as a whole and ])arts of it in drtail. 



The viewpoint of this paper is pre-eminently that of explanation of ].hy- 

 siojrraphic phenomena. A rejiion is selected and discussed i)uri)osely for the 

 presontatit)n of this sort of physio,iirapIiic treatment. The common physi- 

 ographic forms and processes are ,i;iven litth' si)ace. It is held that the 

 topographic luai) coutriltutes such data as size, shaiie. and relationship of 

 topographic forms, and that the text need not he tilled with a mass of 

 rather unnoces.sary and burdensome detail. 'i'lie text should he con- 

 cerned primarily with tlie general conditions which permit of the develop- 

 ment of the particular array of topographic forms, and should he focused 

 especially on the unusual forms and unusual relationships. When these 

 lattt'r tilings are considered the text may have in it then such additional 

 descriptive matter as may he necessary in the explanation of the forms or 

 relationships. Such a program is attempted in the presentation of the 

 material in this i)ai;er. Attention is Hrst centered uiieii tlie factors which 

 have controlled the topograjihic develoi)ment. Tlieii follows a iiresentation 

 of the uiuisual features with sutHci(>nt detail to show what the features 

 are and why tliev exist. 



i-This idea is l.y no iiicaiis new. l.ul it a|)ii.";us to the writer that too little 

 emphasis has l)eeii placed upon it in pliysio.irraphic pai)ers. Kiiftlish physiographers 

 are more appreciative in (his respect than llieir American lieijrhliors. "These fornjs 

 (land forms) never o<inr scattered hapliazard over a region, Imt always in an orderly 



suhordinatlon depending on their iin)de of origin Tile ge(dogical structure 



and tile mineral composition of the roclvs are often the chief causes determining 

 the eliaraiTer of ilie land f<irins of a region. Thus (he scenery of a limestoiu> country 

 depends on the soluliility and permealiility of tlie rocks. leading to the typical Karst- 

 formatioMS of caverns, swallow Indes and underground stream courses, with the 

 contingent plieiionier.a oC dry valleys and natural l>ridges. A sMn<ly beach or desert 

 owes its character to the mohility of its constituent sand grains, which are readily 

 drifted and i)iled u]) in the form of dunes. A region where volcanic activity has 

 lead to the einliedding of <likes or bosses of hard rock aniongst softer strata pro- 

 duces a idain broken by abrupt and isolated eminences." Hugh Robert Mill, Encyclo- 

 lia.Mlia I'.ritaninc.i. Vol. XI. KlcveiUh Kdition, 1>. 6.'!:'.. 



