Jaggar — Volcanologlc Investigations at Kilauea. 215 



Refusion. 



Two deductions may be made at once from the temperature 

 distribution in a blowing cone : 



First, that the more slowly oxidizing gases at 1250° C inside 

 the cone are well above the melting point of the lava walls of 

 the cone, and are also able to oxidize the ferrous iron of the 

 interior surface. The results are seen in the secondary glazes, 

 often brown or silvery with ferric iron, found in the interiors 

 of caverns ; they are seen also in the peculiar cavern stalac- 

 tites ; these glazings mark a refusion of cavern linings so as to 

 destroy the visible vesiculation of a rough surface and to coat 

 the wdiole wnth a smooth mantle of porcellanous aspect. These 

 secondai'Y linings are found everywhere on Kilauea, where the 

 pahoehoe lava has withdrawn from its crusted portions and left 

 cavernous spaces. The linings and stalactitic forms are in 

 great variety of color and texture, and it has been for years 

 apparent to the writer that nothing would account for them 

 satisfactorily except a mechanism of refusion, because of their 

 lithologic distinction from the molten rock. When refusion in 

 a blowing cone goes far enough it results in the glowing 

 " filagree " cone, fused through from within, which may col- 

 lapse and reform, during rising of the lava, again and again. 

 The rising lava is cooler and constructs; the gas chamlier of 

 subsidence is hotter and destroys. 



Furnace effect. 



Second, that a blowing cone is an excellent furnace stack 

 for creating a draught of air into the interior from below, 

 the hottest portions being at the orifices in the summit. 

 This would create a strong updraught, and as all blowing 

 cones contain gas chambers over lava connected in some way 

 with a larger pool, and commonly at the pool level, there 

 would always be an air channel, to supply oxygen to the base 

 of the stack, during the temporary subsidences of the liquid 

 column, which from hour to hour alternate with risings. There- 

 fore rising lava in the stack w^ould yield the purest magmatic 

 gas ; sinking lava should produce more combustion within the 

 edifice. The puffing which has given these cones their name 

 may be a combustion phenomenon ; it is sometimes strilvingly 

 like the noise made by a locomotive. 



Helatlve Coolness of Lake. 



As to the normal lava lake temperatures, it is clear that 

 foundering crusts in a melt of 800°, 900° or even 1000° C. 

 would have no chance for refusion (melting point 1100° to 

 1200° C). On the contrary, in a superfused pure melt their 

 tendency, if not opposed by reheating mechanisms, would be 



