Detailed List of Specimens. 137 



of reddish felspar, with specks of a green substance, probably 

 mica; — resembling a rock from Shap in Cumberland. 



Cape Clinton, between Rodd's Bay and the Percy Islands. 

 — Porphyritic conglomerate, with a base of decomposed felspar, 

 inclosing grains of quartz and common felspar, and some frag- 

 ments of what appears to be compact epidote ; very nearly re- 

 sembling specimens from the trap rocks * of the Wrekin and 

 Breeden Hills in Shropshire. Reddish and yellowish sandy 

 clay, coloured by oxide of iron, and used as pigments by the 

 natives. 



Percy Islands, about one hundred and forty miles north 

 of Cape Capricorn. — Compact felspar of a flesh-red hue, in- 

 closing a few small crystals of reddish felspar and of quartz. 

 This specimen is marked " general character of the rocks at 

 Percy Island," and very much resembles the compact felspar 

 of the Pentland Hills near Edinburgh, and of Saxony. Coarse 

 porphyritic conglomerate, of a reddish hue. Serpentine. A trap- 

 like compound, with somewhat the aspect of serpentine, but 

 yielding with difficulty to the knife. — This specimen has, at 

 first sight, the appearance of a conglomerate, made up of por- 

 tions of different hues, purplish, brown, and green ; but the 

 coloured parts are not otherwise distinguishable in the fracture: 

 — It very strongly resembles a rock which occurs in the trap- 

 formation, near Lyd-Hole, at Pont-y-Pool, in Shropshire. 

 Slaty clay, with particles of mica, like that which frequently 

 occurs immediately beneath beds of coal. 



Repulse Island, in Repulse Bay, about one hundred and 

 twenty miles north-west of the Percy Islands. — Indistinct spe- 

 cimens, apparently consisting of decomposed compact felspar. 

 A compound of quartz, mica, and felspar, having the appear- 

 ance of re-composed granite. 



Cape Cleveland, about one hundred and twenty miles 

 north of Repulse Island. — Yellowish-gray granite, with brown 

 mica; " from the summit of the hill." Reddish granite, of 

 very fine grain ; with the aspect of sand-stone. Dark gray 



* By the terms Trap, and Trap-formation, which I am aware are ex- 

 tremely vague, I intend merely to signify a class of rocks, including several 

 members, which differ from each other considerably in mineralogical cha- 

 racter, but agree in some of their principal geological relations ; and the 

 origin of which very numerous phaenomena concur in referring to some 

 modification of volcanic agency. The term Green-stone also is of very loose 

 application, and includes rocks that exhibit a wide range of characters ;— 

 the predominant colour being some shade of green, the structure more or 

 less crystalline, and the chief ingredients supposed to be hornblende and 

 felspar, — but the components, if they could be accurately determined, pro- 

 bably more numerous and varied, than systematic lists imply. 



Vol. 68. No. 340. Aug. 1826. S porphyritic 



