Jaggar — Volccmologic Investigations at Kilaxtea. 185 



Evidences of Heat from Gas Oxidation. 



Considering what a poor condnctor jDorons basalt is, as illus- 

 trated by the outer walls of the pit, and granting greater radia- 

 tion at the lake surface than laterally, and particularly if the 

 lake is at its hottest near the surface, as suggested by Day and 

 Shepherd, this reheating of flow crusts and buried crags 

 demands special consideration. Furthermore the whole ques- 

 tion of a special mechanism of oxidation heating would seem 

 to be worthy of examination, in view of the new facts concern- 

 ing bench magma and lake magma. The difficulty of intro- 

 ducing water vapor from meteoric sources into a lava column 

 has been found insuperable. Does the same difficulty apply to 

 air, an uncombined mixture of fixed gases, and among them 

 oxygen ? 



In the early part of this paper the writer has indicated five 

 methods by which air may be brought into contact with sul- 

 phur vapor, with hydrogen or with carbon gas in the volcano, 

 and the first two of these are not hypothesis but fact, for sur- 

 face flames are abundant, and suction at grottoes and sinkholes 

 is unquestionable. 



Types of Flames. 



It is singular that geologists who saw Kilauea active could 

 have disputed the existence of flames. They are generally 

 invisible by day and they vary greatly in visible abundance by 

 night. Their color by night is of two distinct kinds, blue- 

 green and yellow. The common banners of flame over the 

 grottoes, seen against a dark background, appear from bluish- 

 green to violet. The sharp flame spears which burst out and 

 play only a few seconds, when crusts on the lake are rent apart 

 over accumulated gas, are bright blue, sometimes appearing in 

 series like jagged saw teeth. These bluish or blue-green flames 

 are very common above spatter cones built over cracks in the 

 benches, and at wall chimneys wdiere the lava froth has per- 

 colated into high talus or cliff cracks and developed a flaming 

 aperture, sometimes a hundred feet (30 meters) or more above 

 the lake. 



It is a question of great interest whether such climbing vents 

 are only the differential mounting of the froth by gas expan- 

 sion, favored by small size of the crevice selected, or whether 

 the heat of oxidation itself, by a sort of blowpiping, fuses and 

 lines its way with a melt re-fused from the rock penetrated. 

 If such refusion by oxidizing gases is possible amid talus open- 

 ings, for example, it is possible on a considerable scale amid 

 the interstices of the crusts of the still hot bench flows, buried 

 by subsidence and overflow, and full of air cavities large and 

 small. 



[Text continued on p. 192.] 



