198 



IGNEOUS ROCKS. 



Upper Light greenish-grey felspathic rock, with inclosed chalce- 



Gallery. t -. , ,. 



dome or cherty concretions. 



Wall-case 4. ^ — g ILIC EOUS AND FELSPIITHIC CONCRETIONARY ROCK 



made of light grey felspathic and bluish chalcedonic sphe- 

 roids. 



108 and 109. — Similar specimens. — Same place as 108. 

 Specimens 106 to 109 are derived from bosses of felspar trap 

 that lie in horizons, not far beneath the Bala limestone, and 

 are, therefore, probably, approximately equivalent to the 

 felspathic rocks under the calcareous ashes of Snowdon, 

 which are partly the equivalents of the Bala limestone. 



110. — Compact felspathic trap. — Yspytty Evan, Caer- 

 narvonshire. Map 74, N. W. Light bluish-grey compact 

 felspathic rock, containing a few felspar crystals. From the 

 same rocks as the preceding. 



111. — Felspathic vesicular trap. — Castell Caer Seion, 



€onway, Caernarvonshire. Map 78, N. E. North end of 

 the felspathic traps of Snowdon, Y Glyder-fawr, Carnedd 

 Dafydd, and Carnedd Llewelyn. 



112. — Ancient celt, mifinished, found in Anglesea, 

 and probably formed from one of the preceding felspathic 

 porphyries of the Snowdon district. 



* 



From 108 to 111 the specimens are all derived from the 

 same set of rocks underlying the ash-beds of Snowdon, &c, 

 and their equivalents. These old lava beds extend from 

 Moel Hebog on the South to Conway on the North. South 

 of Snowdon they form one chief mass. On Snowdon and Y 

 Glyder-fawr the felspathic trap splits into 3 or 4 separate 

 beds. See Section No. i above, and Maps 75, S.E. and 

 78, N.E. The ashy beds near Bettws-y-Coed are the equi- 

 valents of those of Snowdon. 



113. — Blue felspathic rock, with a few cavities. 



Mont 



Map 



74, S.W. 



114. — White felspathic rock, the cavities filled with 

 crystallized carbonate of lime. Craig Rhiwarth, near 



Mont 



Map 74 



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