104 



STRUCTURAL GEOLOGY. 



Fig, 96 below represents a section of alternating belts of limestone and schist, numbered 

 I to mil, to be interpreted. 



It may be that each belt, I, II, III, IIII, III II, is an independent stratum, alike in 

 dip, with mil the highest in the series. This is the simplest explanation. But there 

 may be flexures, and Figs. 97, 98, 99 represent some of the possible methods of interpre- 

 tation. By comparing each with Fig. 96, the relations may be studied out. 



97. 



\\ 



96. 



H«1 



98. 



99. 



In a region of flexed rocks the same bed, as the illustrations show, may come many 

 times to the surface ; and it is therefore easy for the observer to be deceived in such 

 regions as to the number of independent beds. The covering of soil adds greatly to the 

 difiiculty, as the following figures illustrate. When the rock in a region of high dips is 



100. 



101. 



102. 



simply a slate or shale, with no associated stratum of permanent horizon, it is almost 



impossible to decide as to flexures. Such beds bend easily, and may be full of flexures, 



and yet none may be apparent. 



Sometimes an anticlinal flexure has the dips of a synclinal, as in the central part of 



Fig. 102 A. If worn down to a plane (Fig. 102 B), the dips along the center would seem 



to be good evidence of a syncline. Such fan-sha2)ed folds 

 are common on a small scale in schists, and occasionally 

 they may occur on a scale of mountain magnitude. The 

 facts at Mont Blanc in the Alps are explained on the idea 

 of such a fold. 



To reach positive conclusions among the possible 

 explanations, the beds or strata must be carefully com- 

 pared, and also the sides and middle of the several strata, 

 as to texture and all other differences. Besides, search 

 should be made for outcrops that exhibit the limestone 

 and schist in broad anticlinals or synclinals, as in the 



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following cases. In Mount Washington and Greylock of the Taconic range on the boun- 

 dary of western New England, the beds dip at the north end of the mountain mass, nearly 



