388 



PKOCEEBINGS 01^ THE GEOLOGICAL SOCIETY. [May 10, 



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W. of Forth Clais, purple sand- 

 stones, which will be shown to be 

 higher in the series than the green- 

 ish flaggy rocks, strike against the 

 quartziferous breccias, affording 

 further evidence of the occur- 

 rence of a fault in this neighbour- 

 hood. 



It has been stated that at the 

 ruins of IS^un's Chapel the compact 

 quartz rocks are in connexion with 

 the quartziferous breccias. 



At this locality there are seen 

 resting, apparently conformably, 

 on the compact quartz rocks, con- 

 glomerates already referred to as 

 being composed of large and well- 

 rounded masses of quartz imbedded 

 in a purple matrix. These conglo- 

 merates, as here seen, are about 

 30 feet in thickness. 



The same conglomerates are well 

 shown near Clegyr Bridge, where 

 they appear to be conformable to 

 the underlying compact quartz 

 rocks, their dip being towards the 

 S.S.E., at about 80°. In this lo- 

 cality the thickness of the con- 

 glomerates amounts to about 60 

 feet. 



On the N.N'.'W. side of the axis 

 of the quartziferous breccias no 

 compact quartz rocks are recog- 

 nizable ; but some fine-grained 

 yellowish beds of a soft and de- 

 composing nature are seen in con- 

 tact with the quartziferous brec- 

 cias, and are succeeded by purple 

 conglomerates. 



The section on the S.S.E. side of 

 the axis exhibits a good develop- 

 ment of greenish flaggy sandstones 

 identical with those alluded to as 

 occurring at Perth Clais Harbour ; 

 and these sandstones are confor- 

 mable to the conglomerates on 

 which they rest. The greenish 

 flaggy sandstones have been 

 worked, especially at Caerfai; 

 and a small quarry of them is also 



