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MR. W. G. EEARNSIDES ON THE 



[May 19 10, 



dolerite to yield further information. The second series of outcrops 

 is seen on the path up from Penmorfa to Beudy'r-garth, and can be 

 traced continuously for some half a mile along that path, as far as 

 the old Penmorfa nag-quarry on the slopes of Allt Wen. In the 

 quarry it consists of several distinct beds, altogether about 8 feet 

 thick. In this exposure the crumpling of the bedding of the ash- 

 bands under the stresses which produced a slaty cleavage in the beds 

 above and below is beautifully shown, and is most characteristic 

 (see tig. 5, below). 



Pig. 5. — Exposure in the Penmorfa flag -quarry. 



[The above view shows the andesitic ashes of the ' second series' of exposures 

 interstratified with slaty rocks now metamorphosed to desmoisitic flags. 

 The slates, by compression under cleavage-stress, have sufl'ered uniform 

 distortion ; while the andesitic ashes (now almost adinoles) have become 

 crumpled.] 



Due north of the Tremadoc iron-mine the ash-band appears 

 "n, and is underlain by 25 feet of the vesicular rock (4), which 

 itself overlies a dark slate with ill-preserved Dijilograptus, and these 

 three beds follow on together until they are covered by the screes of 



