672 MISS E. M. E. WOOD ON THE [Nov. I906, 



exceptionally well shown. It pitches to the southward, and is over- 

 turned towards the east. The Lower Dolgau Shales are repeated 

 on the east of this fold and continue to the end of the section, 

 where they are folded once more. In this cutting we have an 

 index of the type of folding which is prevalent throughout the 

 district. 



Fig- 2. — Section in the railway -cutting due north of Llawr-y-coed* 

 on the scale of 25 inches to the mile. 





MT*' Bdi iBd 



(a) North Side 



e 



> \ 



ft ,*-■*., 



■'-«f7 Br Bd.' Bd* 



(b) South Side 



Bd 2 = Middle Purple Sub-group of the Dolgau Beds. 

 Bd x = Lower Green Sub-group of the Dolgau Beds, with graptolitic 

 bands at the base. 



The section in the southern bank of the cutting, although not 

 quite so clear, presents some differences. As far as 97 paces from 

 the bridge the beds exposed agree in all particulars with those 

 in the northern bank, but at this point purple mudstones are 

 seen in the bank about 10 feet from the ground. This purple band 

 comes down to the level of the railway-line 12 yards farther on, 

 and extends for a distance of 21 yards, occupying the whole height 

 of the bank, with the exception of the topmost part. It then rises 

 up again towards the top of the bank, leaving the base to be 

 occupied by the underlying green beds of the Lower Dolgau Group. 

 The disposition of the strata on the two sides of the cutting is best 

 understood by an examination of the two accompanying sections 

 (fig. 2, a & b, above), while the facts can be readily explained if we 



