30 The Rev. D. Williams's Cliff Section of Lundy Island. 



6. Dark olive-gray hornblende porphyry, passing into a 

 black bottle green colour with disseminated crystals of cal- 

 careous spar, at times remote, at others so thickly grouped 

 together as almost to usurp the base, and nearly to touch each 

 other. 



7. Light and olive-gray compounds of clay, felspar, quartz 

 and lime, parted out in inch-thick layers and lesser lamina- 

 tions of schist by delicately thin plates of fibrous calcareous 

 spar, passing into a calcareous trappean foliated marl, and 

 marl rock, sometimes more thickly laminated and without the 

 calcareous spar partitions, at others a clay schist. At the foot 

 of the section on the N.N.E., where 6 and 7 is as if wedged 

 in, and curves out in No. 5 *, a conglomerate of fine gravel in 

 a base of felspathic schist or greenish-gray volcanic ash, per- 

 taining rather to No. 5 than to 6 or 7, is distinctly seen. 



8. Black, finely granular crystalline hornblende trap, feebly 

 calcareous, rendered somewhat porphyritic by crystals of glassy 

 felspar, so nearly black as only to be detected by the light 

 reflected from their cleavaged facets; it also contains sparely, 

 a green mineral like olivine, more irequently iron pyrites, at 

 times white on exposure; and commonly small white spherules 

 of calcareous spar. 



9. Unctuous clay schist, evidencing no alteration from its 

 contact with No. 8, differing little or nothing in composition 

 and texture from much of No. 7. 



10. Flinty, talcose clay, and felspathic schists and slates, 

 in indefinite alternations. 



11. Buff and ochreous rusty-coloured porphyry. 



N.B. The unshaded parts represent a lofty cavity at either 

 extremity, caused by the more ready decomposition of the 

 calcareous products. 



It is a notable fact, that after the confines of the slate and 

 granite at Lundy, a distance of half a mile, we have not a 

 vestige of a granite vein ; the same intermediate substances, 

 Nos. 6, 7 and 8, are met with at either extremity, and at in- 

 tervals between them, and the immediately bounding schist 

 and slate show no amount of alteration, or so little, that re- 

 garding those intervening substances, and their mineral rela- 

 tions with, and transition into, the granite, the inference that 

 the schists had metamorphosed the granite or the original 

 granite lava, is far more probable and defensible than an in- 

 verse supposition. 



From Nos. 1 to 10 inclusive, we had so many graduated 



* This remarkable feature in the section is at nearly the base of the cliff, 

 and is sometimes quite obscured by shingle, which shifts theie very much 

 at times. 



