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FELSPATHIC PORPHYRIES, ETC., SNOWDON SERIES. 197 



102.— Felspathic trap.— Esgair-felen Y Glyder Fawr, 

 Llanberis, Caernarvousliire. Map 78, S.E. Grey compact 

 felspathic rock, with patches of pink felspar. Upper 

 part filled with elongated cavities, partly empty, partly 

 filled with pink felspar, partly with siderite, and some with 

 ochreous brown iron ore, from the decomposition of the 

 latter mineral. 



From the northern continuation of the highest of the 

 three beds of felspathic trap that form the cliff of Clogwyn 

 du'r Arddu. 



103. — Concretionary felspathic porphyry Y 



Glyder Fawr, Llanberis, Caernarvonshire. Map 78, S.E. 

 Bluish-grey felspathic rock, with crystals of fe'lspar,' 

 full of spheroidal felspathic concretions, themselves por- 

 phyritic. 



From the felspathic trap north of Pen-y-Gwryd, between 

 the top of the Pass of Llanberis and Capel Curig. Equi- 

 valent to a high part of the Snowdon felspathic traps of 



Clogwyn du'r Arddu, &c. 



104. — BrECCIATED FELSrATIIIC TRAP. 



Snowdon, Caernarvonshire. Map 75, N. E. __ uauiou . 

 grey felspathic rock formed of angular fragments of fel- 



Crib Goch. 

 Dark bluish- 



spathic rocks. 



Snowdon and Moel Hebo°:. 



This specimen belongs to one of 8 small isolated patches 

 of compact felspathic trap that overlie the ashy rocks of 



-_ t TLT , TT , ^ j^ . g genera -Qy C0 l Umnarj an( J 



once overlying the ash, formed a great continuous sheet of 

 lava, the greater part of which has been destroyed by 

 denudation. 



105 — Calcareous amygdaloid Moel-yr-Ogof, Bedd- 



gelert, Caernarvonshire. Map 75, N. E. Green° felspathic 

 rock, full of cavities. Containing cole spar on the surface. 

 The lime has been dissolved out of the cavities. 



From an outlying patch of the above , lying on the ashy 



beds of Moel Hebog. 



106 — Compact felspathic 



trap — Digoed, 31 miles 



south of Bettws-y-Coed, Caernarvonshire. Map 75, N 



Uppeb 

 Gaxlekt. 





Wall-case 4 



