I9II] ON VOLCANOES. 219 



Friday, June 1 6. — Overcast again — little wind but also little 

 moonlight. Jimmy Pigg quite recovered. 



Went round the bergs in the afternoon. A great deal of 

 ice has fallen from the irregular ones, showing that a great deal 

 of weathering of bergs goes on during the winter and hence that 

 the life of a berg is very limited, even if it remains in the high 

 latitudes. 



To-night Debenham lectured on volcanoes. His matter is 

 very good, but his voice a little monotonous, so that there were 

 signs of slumber in the audience, but all woke up for a warm 

 and amusing discussion succeeding the lecture. 



The lecturer first showed a world chart showing distribution 

 of volcanoes, showing general tendency of eruptive explosions to 

 occur in lines. After following these lines in other parts of 

 the world he showed difficulty of finding symmetrical linear dis- 

 tribution near McMurdo Sound. He pointed out incidentally 

 the important inference which could be drawn from the discovery 

 of altered sandstones in the Erebus region. He went to the 

 shapes of volcanoes: 



The massive type formed by very fluid lavas — Mauna Loa 

 (Hawaii), Vesuvius, examples. 



The more perfect cones formed by ash talus — Fujiama, 

 Discovery. 



The explosive type with parasitic cones — Erebus, Morning, 

 Etna. 



Fissure eruption — historic only in Iceland, but best prehis- 

 toric examples Deccan (India) and Oregon (U.S.). 



There is small ground for supposing relation between ad- 

 jacent volcanoes — activity in one is rarely accompanied by ac- 

 tivity in the other. It seems most likely that vent tubes are en- 

 tirely separate. 



Products of volcanoes. — The lecturer mentioned the escape 

 of quantities of free hydrogen — there was some discussion on 

 this point afterwards; that water is broken up is easily under- 

 stood, but what becomes of the oxygen? Simpson suggests the 

 presence of much oxidlzable material. 



CO2 as a noxious gas also mentioned and discussed — causes 

 mythical ' upas ' tree — sulphurous fumes attend final stages. 



Practically little or no heat escapes through sides of a 

 volcano. 



