120 W. M. DAVIS RELATION OF GEOGRAPHY TO GEOLOGY 



The properly explanatory definition of these terms enforces this conclu- 

 sion. A delta, for example, is not properly defined simply as having a 

 flat lowland surface at a river mouth, nor j^et as having been formed by 

 the deposition of river-brought waste at the river mouth, but as having a 

 flat lowland surface, because of having been formed by the deposition of 

 river-brought waste at the river mouth. Similarly a dissected peneplain 

 ought not to be defined as an upland district of subequal altitude, tran- 

 secting rock structures indifferently and here and there interrupted by 

 valleys, nor yet as a district which once stood lower and was then worn 

 down to low relief by normal erosional processes, and which w^as after- 

 ward uplifted and in this new altitude partly cut down by its revived 

 rivers ; but as an upland district, in w^hich the accordant hilltop surface 

 transects the rock structures indifferently because of having been worn 

 down to low relief by normal erosional processes during a former lower 

 stand of the region, and which is now here and there interrupted by val- 

 leys because of the revival of erosive processes in virtue of later uplift. 

 Neither the empirical statement of present fact nor the geological ac- 

 count of origin suffices in such definition. A double definition is neces- 

 sary in which geological origin is closely associated with present form, for 

 thereby the essentially geographical nature of these terms is made clear. 

 The same is true of the term morvan. A morvan is not best defined 

 simply as a hard-rock upland, whose resistant mass descends rather 

 smoothly under a neighboring lower district occupied by stratified rocks, 

 nor yet as a region that has been through such and such changes during 

 its long past history, but as a region that exhibits a hard-rock upland or 

 highland bordered by a lower land of slanting stratified rocks because of 

 having suffered such and such changes in its long past history; and thus 

 defined, morvan may be added to the growing list of well established 

 geographical terms. 



Part IV. The Eelatton of Geography to Geology 



GEOGRAPHY IS THE GEOLOGY OF TODAY 



The description of the Colorado Front Eange as a morvan will, I trust, 

 be regarded as properly geographical by nearly all members of this So- 

 ciety; but it may still be that some of the more serious objectors may 

 refuse to be blinded by the use of a mere term, and may declare that 

 no such subterfuge can conceal from them the essentially geological 

 quality of any explanatory description that i« essentially based on the 



