140 



F. A. Perret — Lava Fountains of Kilauea. 



often iridescent sheen greatly resembling iu appearance the 

 oxidized surface of molten metal in a plumber's solder pot. 

 As the flow is divergent, this skin is pulled apart, forming a 

 series of radiating " bright lines" which, if the activity is 

 moderate, often constitute, at night, the only luminous por- 

 tion of the surface, exception taken of the fountains. The 

 film gradually thickens by accretion from below and changes 

 from a tough, flexible skin to a true crust which, is brittle and 

 cracks under unequal pressure. 



Fig. 1. 



Fig. 1. Lava Lake, Halemaumau. From east brink, July 1911. 



Suddenly a large, circular area of the lake surface, in the 

 center of which a fountain is to appear, is strongly agitated as 

 though a violent up-thrust had been given from below, and 

 in a few seconds there rises through the surface skin a beautiful 

 dome-topped column of perfectly liquid lava — bright orange- 

 yellow in clear sunlight — bursting upward in a shower of fiery 

 drops or boiling, dome-shaped, for a few moments and then 

 subsiding into the lake amid surging waves as the parted 

 surface-lavas close over the spot, where smaller jets continue 

 spouting and a general commotion prevails for some time. 

 Nor even so is the phenomenon at an end, for the cooling of 

 the fountain lava, and the reduction of its volume by contact 

 with air and the loss of its gases, give to it a greater density, 

 and this, together with the acquired momentum of its subsi- 

 dence, favors rapid sinking and a local void with a lower surface 



