PERTINENCE OF EXPLANATORY PHRASES 99 



GEOGRAPHICAL PERTINENCE OF EXPLANATORY PHRABE8 



Let me show explicitly how closely pertinent, how directly helpful 

 every element of the description of the Front Eange is in forming a just 

 conception of the existing landscape. The range was described as "a 

 highland of disordered and generally resistant crystalline rocks, which 

 shows signs of having been long ago worn down from its initially greater 

 mass to a surface of faint relief, slowly depressed and more or less broadly 

 buried under a heavy cover of sedimentary strata." That condensed 

 statement gives us a sufficient introductory understanding of the com- 

 pound structural mass with which we have to deal. Next : "As the result 

 of a general uplift a part of the compound mass west of a pronounced 

 monoclinal displacement along a north-south line came to stand above the 

 rest, and thus the province of the mountains on the west was marked off 

 from that .of the less uplifted plains on the east." This statement makes 

 clear the attitude in which the compound mass was placed at the begin- 

 ning of an important cycle of erosion, the work of which is at once inti- 

 mated as follows : "The form of the highland shows that the whole region 

 advanced far through the cycle of erosion introduced by the monoclinal 

 uplift." From this the hearer may easily infer what is at once directly 

 stated, namely, "that the resistant underlying crystalline rocks of the 

 mountains area were stripped of their cover and worn down to a gently 

 rolling peneplain, diversified with irregularly scattered monadnocks rising 

 singly or in groups with a relief of from 500 to 2,500 feet." This is a 

 most pertinent matter, for herein we find the explanatory conception of 

 the broad surface of erosion, which is now seen in the highland of the 

 Front Eange. It might have been expected that scattered monadnocks 

 would survive, even though much of the surface was peneplained, because 

 the crystalline rocks were described as generally resistant, thus implying 

 the occurrence of some variation in their resistance; and again that the 

 surviving monadnocks would be irregularly scattered singly or in groups, 

 because the structure of the crystallines was briefly described as "dis- 

 ordered." Had systematic trends characterized the arrangement of the 

 rocks, and had pronounced difference of resistance characterized their 

 composition, those structures would have been mentioned earlier; the 

 absence of such mention indicates the absence of such structures and sug- 

 gests the inference of scattered monadnocks. Although no explicit state- 

 ment is made as to what happened during the same cycle of erosion in tlie 

 plains area, it is easily inferred that the weak strata there exposed must 

 have been worn down to extremely faint relief, because the resistant crys- 

 tallines of the mountains area are explicitly stated to have been as a whole 

 worn down to a gently rolling peneplain. 



