146 



VOLCANIC ROCKS OF TENERIFFE 



Upper 

 Gallery. 



Wall-case 1. 



but for an opening in one place ; but in the interior there 

 is a gentle slope for about 106 feet. 



The crater has lone 



ceased to emit flame, but it still gives vent to 



vapours 



W 



aqueous 



140.— Lava, from the outer surface of the stream, of a 

 twisted form, showing the result of a viscous flow. 



1 4 1 .—Lava, with a wrinkled surface, the result of flow- 



"1 • 1 • • 



ing while in a viscous state. 

 142. 



From the Ice Cavern. 



Black lava, overlying the Pumice at Alta Vista, 

 showing a tendency to assume spheroidal forms, and the 

 smooth planes of joints. 



143 — Pumice, from A Ita Vista. 



144.— Pitch-stone lava, lying under the pumice at 



Alta Vista. 



145. — Sulphur, from the interior of the crater. 



146. — Sulphate of alumina and iron, from the in- 

 terior of the crater. 



147. — Sulphate of iron and alumina, containing also 

 insoluble matter — From the interior of the crater. 



Wall-case 2. 



w 



from the Island of 



Mr. Charles Darwin. F. 



1 to 14 e, are varieties of lava, of which 4 to 8 and 10 are 

 more or less cellular, while 9, 11, and 13 are more compact. 

 14 to 14 e, as well as 106, from Chatham Island, from the 

 superficial parts of a lava stream, are especially remarkable 

 for their singular forms. They are described as being scat- 

 tered over the surface of the ground, presenting the appear- 

 ance of logs and branches of trees. 



lo to 26 represent varieties of laminated beds, which 

 alternate with and pass into obsidian. 



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