F. A. Ferret — Floating Islands of Halemaumau. 277 



The roasting of the mass of rock, with its lower portion 

 immersed in seething lava and its emergent part exposed to 

 air and moisture, results in a complicated process of decompo- 

 sition with evolution of vapors which, naturally, tend to rise 

 in the fissures and lines of fracture, thus issuing principally 

 from the summit of the island. Now, it is well known that 

 such gas action inevitably enlarges the passages and it is inter- 

 esting — and may be permissible — to imagine that, in time, 

 these channels might be widened and extended to the liquid 



Fig. 2. 



Fig. 2. Showing grotto under central neck into which the surface lava 

 was flowing and falling into a void below. 



below in which case the ascending gases would bring up lava, 

 and a true volcanic chimney would be established within an 

 already formed containing edifice. This suggests the possi- 

 bility of an ordinary mountain — formed, or in process of 

 formation — becoming a volcano, whose ashes and lavas would 

 soon obliterate the original contours. 



That the probabilities are all against this will be understood 

 from the strongly compressed lower portion of the anticlinal 

 type of fracture, i. e. a fracture in an anticlinal fold as con- 

 trasted with that of a synclinal fold which is open at the bot- 

 tom to the intrusion — and therefore to the comparatively facile 

 subsequent extrusion — of the volcanic materials from below. 

 When it is considered how rarely, even under these compara- 



