148 F. A. Perret — Lava Fountains of Kilauea. 



maintain a remarkable constancy of position in the area lying 

 approximately over the Halemaumau conduit, among which 

 the one known as "Old Faithful" is preeminent. It would 

 seem that the gas bubbles, rising through the liquid mass, cre- 

 ate a path of less resistance which tends to be perpetuated by 

 further emission. A striking example of this was seen at 

 Etna in 1910, where the loci of the explosions were continued 

 as the stream flowed downward (fig. 7). 



The writer holds that the fountains of Kilauea are caused 

 by the rise and expansion of large bubbles of gas in a hyper- 

 mobile lava. The jets of incandescent, liquid lava at Strom- 

 boli, Vesuvius, Etna, etc.,* are true lava fountains in which 

 the spatter phase prevails because of the somewhat greater 

 viscosity of the lava. 



That some forms of volcanic action are quiet and non-explo- 

 sive need not signify that they are non-gaseous. Eruption is, 

 fundamentally, not explosion but emission of gas. Explosion 

 occurs when the emission is obstructed and the gases have 

 acquired sufficient tension to remove the obstruction. The 

 writer believes that the great outpourings of basalt during 

 fissure eruptions were accompanied by the emission of enor- 

 mous quantities of gas. 



Geite may well be the condensed gas deduced by Arrhenius 

 working up into magma which finally separates out into gas 

 and lava. 



Posillipo, Naples, 

 November 27, 1912. 



* An example may be seen over the crater in fig. 7. 



