too Ot'Tll\l-i MILD-GEOLOGY PARTI 



rock does not occur higher up. hut has its upper limit 

 somewhere near the point where the fragments in the 

 a disappear. While these particular ruck - chips 

 cease, others of some different rock may be found to 

 increase in number, and another zone of rock may be 

 shown and traced in a similar way. 



In many parts of the country where, owing to the 

 depth to which the rocks have decayed from the surface 

 downward, no satisfactory < s of them can he 



found on the fields, or even in the valleys and brooks, 

 sections may be detected on the roads where the super- 

 ficial cover of disintegrated material has been worn down 

 or cut through. 



In nothing is the highest type of a field-geologist better 

 displayed than in the exhaustiveness and sagacity with 

 which, in the absence of all other evidence, these various 

 little indications of the geology of a district are sought 

 for, found, and marshalled in their proper places, so as 

 to bear witness to the distribution and probable structure 

 of the rocks. Such an observer is able in many cases to 

 trace lines, with a near approach to accuracy, over 

 ground which a less skilled student would pronounce to 

 be a blank. 



It must often happen, however, that the ground is so 

 obscured by superficial accumulations, such as vegetation, 

 soil, gravel, and clay, that no indication whatever can for 

 considerable intervals be found as to the nature of the 

 solid rocks underneath. Under these circumstances the 

 geologist, when no boring or mining operations are at 

 his service, must do the best he can, by examining all 

 the surrounding ground, to determine what lies below the 



