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VOLCANIC ASHES, ETC., SNOWDON SERIES. 185 



75, N.E. Bluish-grey felspathic sediment, with a little 

 calcareous cement; weathers very unequally, giving the 

 outer surface a rough scoriaceous appearance. 



ash. — Clogwyn du'r 



32. — Brecciated 



felspathic 



Arddu, Snowdon, Caernarvonshire. 



Map 



7o 



N.E. 



Greenish-grey felspathic sediment, with included angular 

 felspathic fragments, which project on the weathered 



surface. 



°3. 



Volcanic ash— Dolwyddelan, Caernarvonshire. 

 Map 75, N.E. Dark greenish brecciated and scoriaceous- 

 looking volcanic ash, enclosing rough angular, and a few 

 rounded felspathic 

 brittle. 



fragments. 



Exceedingly hard and 



34— Felspathic ashy breccia — Castell Cader Din- 



Mer 



shire. Map 74, KW. Roughly bedded ; dark-grey rock, 

 with small included fragments of grey felspathic sub- 

 stances. Weathers brownish-grey. 



35— Felspathic breccia — Same locality as 34. Light- 

 grey rock, made up of angular felspathic porphyritic frag- 

 ments, imbedded in a felspathic base, containing crystals of 

 felspar. Bleached and weathered surface, very irregularly 

 eroded, and covered with ferruginous stains. 



36— Felspathic sediment— Same locality as 35. Dark 

 greenish-grey, with fragments of black sandy slate, and 

 crystals of white, brown, or yellow felspar fragmentary and 

 entire, some much decomposed. The specimen has a coarse 

 slaty structure, and gives a strong argillaceous odour. 



The mechanical origin of this rock is very apparent, the 

 crystals being truly and mechanically imbedded in felspa- 

 thic and slaty sediment, containing a few grains of quartz. 



37— Sandy felspathic ash— Same locality. Similar 

 to the last, but of a lighter colour, with larger fragmonts of 

 ™ d r ™ k > and numerous broken and entire crystals of 



(Orthis), the 



fel 



spar 



shells of which have been carried away in solution by the 

 percolation of rain water. The fossils in this specimen, 



TJPPEB 



Gallery. 

 Wall-case 4 



I 



I 



