Jaggar — Volcanologic Investigations at Kilauea. 193 



of the liquid lava which emit gas without flame, there is in 

 daylight a distinct yellow-brown fume at the places where the 

 blue flames occur (tig. 9^, over sinkhole), and higher there is 

 a condensation of pale blue fume which expands above into a 

 larger cloud faintly blue. This blue smoke is very hot and may 

 be nearly invisible, but it is the most irrespirable of the Kilauea 

 fumes, and the odor is that of sulphur dioxide. It probably 

 contains also the trioxide. The gas from the smaller bubblings 

 makes no perceptible fume and has very little odor, but is 

 sometimes oppressive as though with carbon dioxide. The 

 white smoke that rises from cracks in the benches and crags 

 is weakly sulphurous but quite respirable, and appears to be 

 in the main a mixture of moist air and unburned sulphur. In 

 working to leeward of Halemaumau one learns to dread the 

 intolerable blue fume from the sustained continuous fountains ; 

 at night these are seen to be surmounted by flames, so that 

 the conclusion aj)pears warranted that the surface oxidation 

 which they represent is mainly that of sulphur vapor. 



Gases Responsible for Flames. 



It thus appears that of the three combustible gases hydro- 

 gen, carbon monoxide and sulphur, the last is most in evidence 

 as surface flames, the second, along with impurities, may be 

 represented by rare flames but mostly achieves its combustion 

 below the surface, while the tirst, namely hydrogen, flashes to 

 water vapor in depth, and is not (unless by spectroscopic means) 

 to be diagnosed \>y itself as flame at the surface. A residue of 

 both gases is mixed with the sulphur. 



By its stronger aflinity for oxygen, hydrogen w^ould certainly 

 be the flrst of the combustible gases in the mixture to achieve 

 oxidation below the surface if oxygen were available ; we And 

 it in the Day and Shepherd analysis of even the surface gases 

 in larger amount than the carbon monoxide. In view of the 

 evidence that some oxygen reaches the lava column below the 

 visible lake surface from downward suction and from engulfed 

 talus slabs and crusts, and that in the gas-collecting apparatus 

 water vapor condensed abundantly, it seems hardly admissible 

 that none of the water should be produced by combination of 

 hydrogen with atmospheric oxygen. If any of it is produced 

 by sub-surface combustion of hydrogen, then w^e have in such 

 combustion a formidable heating agency to be reckoned with 

 for whatever depth air enters the lava. In less degree but in 

 like fashion air would at these high temperatures (850° to 

 1150° C.) react powerfully with carbon monoxide and sulphur 

 vapor to produce heat."^ 



* Dr, Shepherd suggests (oral) that silicon hydride (SiOo + 4H2 = SiHi + 2H2O) 

 is a combustible unstable gas formed at high temperature, possibly present 

 at Halemaumau, and that he has detected the odor of carbon oxy-sulphide 

 (COS) there. The latter is a lower temperature product, also inflammable, 

 and might be expected in the bench magma. 



Am. Jour. Sci.— Fourth Series, Vol. XLIY, No. 261 -September, 1917. 

 14 



