154 



TUFAS, ASHES, AND CINDERS : ASCENSION. 



Upper 

 Galleey. 



"Wall-case 2. 



61. — Breccia, composed of fragments of trachyte and 

 obsidian in a trachytic base, which also contains a few 

 crystals of glassy felspar. 



62. — Breccia, composed of fragments of pitchstone and 



pearlstone in a trachytic base. 



63. — Pumice (porous felspathic volcanic scoria). 



64. — Pumiceous conglomerate. 



65. — Volcanic ash (in a bottle). 



66. — Consolidated volcanic ashes, enclosing a Pecten. 



67. — Volcanic sand (in a bottle). 



68. — Soft white pumiceous tufa. 



69, 70, 71, & 72. — Varieties of trachytic tufa (in 

 bottles). 



73. — Bright-red vesicular tufa. 



74. — Fine-grained, partially consolidated tufa or pepe- 

 rino, with coarser loose scoriae. 



75 & 76. — Peperino, formed of volcanic sand and ashes 

 cemented together. 



77. — Black trachytic tufa or Peperino, from the 



bottom of the volcano. — St. Vincent. 



78. — Scoriaceous lava or pozzolana. — Sheepwalk. 



— Scoriaceous lava or pozzolana. — High Peak. 



79 & 80. 



81. — Volcanic scoria and ashes. 



82, 83, & 84. — Volcanic scoria, cinders, and slags. 



Volcanic Bombs. 

 85.— Volcanic bomb of obsidian. — " The specimen was 



foundj in its present state, on a great sandy plain between 

 the rivers Darling and Murray, in Australia, and at the 

 distance of several hundred miles from any known volcanic 

 region. The external saucer consists of compact obsidian, 

 of a bottle-green colour, and is filled with finely cellular 

 lava, much less transparent and glassy than the obsidian. 

 The external surface is marked with four or five not quite 

 perfect ridges. The lip of the saucer is slightly concave, 

 exactly like the margin of a soup-plate, and its inner edge 

 overlaps a little the central cellular lava. This structure is 





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