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INTRUSIVE IGNEOUS ROCKS. 



199 



115. — Compact felspathic rock, with a few inter- 



position 



Ffelspa 



j 



Mont 



W.N. W 

 Map 



It is uncertain whether 113 and 115 are of the date of 

 the Snowdon traps or of those of Cader Idris and the 

 Arans ; the latter is probable. It is also uncertain whether 

 they are contemporaneous or intrusive. 



Intrusive Igneous Rocks, North Wales. 



rian and 



Rocks intruded among and altering the Camb 



Lower Silurian strata. 



116— Hornblende porphyry.— Ridge of Cader Idris 



Merionetl 



Map 



N.E. Light grey felspathic base, containing small crystals of 

 light and dark green hornblende, slightly bleached on the 

 exposed edges. 



This specimen is from the cliffs on the north side of 



Cader Idris, 



and though 



the rocks here lie between the 



strata (see Section No. a above, No. 116,) 



to be intrusive, as they break across the strike 'on Mynydd 

 Pennant, east of Lyn Cae. Map 



N.E. 



base with 



a 



117.— Syenite.— Two miles north-west of Ffestinio°- 

 Merionethshire. Map 75, N.E. Greenish grey felspathfc 



little quartz, with irregularly interspersed 



*gmeuia 01 a platy hornblende (bronzite). 



From a large boss of intrusive Syenite piercing the Lin- 

 gula flags, and altering them all round the points of junc- 



) 

 Bwlch-yr-Hcndref, near Capel 



tion. 



118. 

 A r th Off, 



Greenstone. 



6 miles south-west of Dolgelley, Mer 



■ ap 59, N.E. Dark green hornblende base, containing 

 crystals of white potash felspar and large crystals of a platy 

 variety of hornblende. - 



UrpER 

 Gallery- 



Wall-case 4- 



