ON CLEAVAGE AND FOLIATION IN ROCKS. 



377 



between the lines* 

 Fiff. 8. 



The 

 Fig. 9 



Fig. 10. 





general result of that inquiry, as regards this tract 

 "" of country, may be 



understood by refer- 

 ence to the drawings 

 marked 8, 9. 



In his description 

 of these sections, Mr. 

 Sharpe calls attention 

 to the fact, that " in 

 this wide area we have 

 only one axis of the 

 cleavage, but there are 

 several anticlinal and 

 synclinal axes of the 

 stratification ; these 

 (with the exception 

 of the central one at 

 Rhaiadr Cwm) have 

 no effect on the clea- 

 vage, which follows its 

 own direction indiffer- 

 ently through beds 

 dipping in opposite di- 

 rections. Still there is 

 so much relation be- 

 tween the direction of 

 the cleavage planes 

 and the position of the 

 beds, that we might 

 infer from this section 

 alone that the cause 

 which produced the 

 cleavage of the rocks 

 had helped to deter- 

 mine the elevation of 

 the beds." This infer- 

 ence is not only ob- 

 scure, but seems op- 

 posed to those already 

 established, which as- 

 sign priority of date to 

 the movements of the 

 strata, and more exten- 

 sive symmetry to clea- 

 vage than to inclina- 

 tion of beds. 



The region thus 

 sketched by Mr. 

 Sharpe was previously 

 traversed by mvself in 

 1836 and 1843" with a 

 view to measured re- 



* Sharpe, 1846 ; " On 

 Slaty Cleavage," Proc. of 

 Geol. Soc. p. 90, &c. 



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