﻿582 



DR. 



T. GPvOOil AND ME. P. LAXE ON THE [XoV. I908, 



than that of the fault, then an overthrust will bring newer beds 

 upon the top of older (fig. 14, p. 581). It is impossible, therefore, 

 from the mere fact that the Dolhir Pault brings higher on to 

 lower beds, to infer that it is necessarily a lag-fault. 



In the section, fig. 1 (p. 552), it will be observed that the beds 

 above the fault dip at a lower angle than the fault itself, while the 

 beds below dip at a higher angle. This, as will be seen by refer- 

 ence to fig. 15, is what may happen if the fault affects the margin 



Fig. 15. 



either of an anticline or of a svncline 



on the southern margin of the Llangollen Basin 



and the Dolhir Fault lies 

 and also on the 



northern margin of the Berwyn Anticline. The diagram shows that 

 either an upward or a downward movement, if of the proper extent, 

 would bring the higher beds A, B, C (dipping at a low angle) upon 

 the top of the lower beds 1, 2, 3 (dipping at a high angle). In 

 such a case as this, it is clear that the anticline and syncline were 

 formed before the fault. 



The relations of the beds, therefore, tell us nothing of the 

 direction of movement ; and the only evidence that we can find is 



