Geological magazine . oscope shows the usual triclinic felspars and green pyroxene,the felspar crystals and fragments being especially abundant, togetherwith fine volcanic dust and glass fragments. There are also veryslender needles of a highly refracting yellow-brown mineral, whichhas much of the appearance of rutile—a mineral scarcely to beexpected in such a connexion. Falcon Island came into existence owing to a volcanic eruptionwhich occurred in the year 1885.^ The main mass of the islandconsists of a fine grey ash, mostly quite incoherent, but containingcrumbling lumps. The microscope sho
Geological magazine . oscope shows the usual triclinic felspars and green pyroxene,the felspar crystals and fragments being especially abundant, togetherwith fine volcanic dust and glass fragments. There are also veryslender needles of a highly refracting yellow-brown mineral, whichhas much of the appearance of rutile—a mineral scarcely to beexpected in such a connexion. Falcon Island came into existence owing to a volcanic eruptionwhich occurred in the year 1885.^ The main mass of the islandconsists of a fine grey ash, mostly quite incoherent, but containingcrumbling lumps. The microscope shows this to be a volcanic dustsimilar to that so widely dispersed during the eruption of is composed largely of comminuted crystals, among which arerecognized felspars, some with twin-lamellation, green augite, and 1 A Visit to the newly emerged Falcon Island, Tonga Group, S. Pacific, byJ. J. Lister, Proceedings of the Eoyal Geographical Society, March, 1890. Geol. Mag. 1891. Dec. III. Vol. VIII. PL Eemains of Hylonomus Lyelli, Dawson, 1859. Coal-Measures, South Joggins ; Nova Scotia. (1) Cranial boues and mandibles; (1«) Sternal and shoulder bones; (2) Mandible ; (3) Humerus, ribs and vertebrae ; (4) Hind limb; (5) Pelvis; (6) Caudal vertebrte. A. Harl-er—Rocks from the Tonga Islands. 257 a rather fibrous rhombic pyroxene. Some of the felspars areandesine, but they are not all of one variety. With these mineralsoccur many fragments of yellowish glass, often with very irregularshape and concave boundaries, such as would arise from the breakingup of pumice. The coarser accumulations would rather be termed have a rough and often porous texture, and are largely com-posed of bomb-like ejectamenta, a quarter or half an inch in diameter,besides pieces of vesicular and pumiceous lava. The interspaces areoften partly vacant, with a dusty lining. These agglomeratic rocksare grey or yellowish, but become red or brown by weathering. Mr. Listers col
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectgeology, bookyear1864
