110 AV. M. DAVIS RELATION OF GEOGRAPHY TO GEOLOGY 



too many links, and thus to encumber their geographical essays with so 

 many inferred facts of remotely past occurrence, little related to present 

 facts, that the reader's attention is distracted from instead of concen- 

 trated on the facts of present form. 



Let me emphasize this principle by pointing out that the exclusion of 

 irrelevant geological matter requires careful consideration. There is too 

 frequentlv a tendency among geographers of the modern or evolutionary 

 school to make mention of geological technicalities, which, however im- 

 portant they may be in geology, are unessential and irrelevant in geog- 

 raphv. Many geographers would, for example, introduce into such a 

 description as that given above for the Colorado Front Eange petro- 

 graphical and geological names for the deformed and generally resistant 

 crystalline rocks of the highlands, and for the members of the heavy cover 

 of sedimentaries now seen in the adjacent plains, and they would mention 

 also the geological dates of the early planation, of the monoclinal defor- 

 mation, of the later peneplanation, and of the final uplift of the district 

 to its present altitude. All such matters are truly essential in a geo- 

 logical description, but they are unessential, irrelevant, distracting, and 

 obstructive in a geographical description. If a better understanding of 

 the appearance of the existing landscape can be gained by adding any one 

 of these geological terms, then let it, of course, be added at once: but if 

 not, let it be as carefully excluded. 



It may well be that in his preparation for writing the description of a 

 mountain range a geographer has occasion to examine many geological 

 reports, in which he will repeatedly come upon such matters as names of 

 formation, dates of unconformities and deformations, and so on. When 

 he finally abstracts those parts of his accumulated information, which are 

 to serve for a truly geographical description, all names of formation 

 which imply geological dates and all names of fossils and of rare minerals 

 will be carefully excluded. True, if a geographer wishes to make his geo- 

 graphical description serviceable to geologists, he may well enough include 

 some mention of purely geological matters that are geographically irrele- 

 vant; but in the same way he might make his geographical essay useful 

 to mathematicians by including some mention of the method of calculat- 

 ing logarithmic tables, or to classical philologists by adding some remarks 

 on the increase of certain Latin nouns in the genitive. All such matters 

 have their value somewhere and are all interesting to those who are inter- 

 ested in them ; but none of them deserve a place in a geographical descrip- 

 tion unless they aid in the object of that description, namely, the por- 

 trayal of the existing landscape. If some of mv hearers are skeptical en 

 this point let them settle their doubts by making critical trials of pure 



