Jaggar — Yolcanologic Investigations at Kilaum. 207 



and through for scores of feet one month from the time when 

 live lava was overflowing, as in the collapsed west pit of 

 February, 1917, points to profound and rapid oxidation with 

 strong evolution of heat. Moreover, on March 14, 1917, in 

 this same region, after subsidence of the lake of 84 feet (26'") 

 in six weeks, the weathered pahoehoe flow surfaces, dead since 

 January, began in places to glow with red heat, though 70 

 feet (21"") above the lake and quite remote from any live lava. 

 This reheating appeared to be gas oxidation through small 

 crevices. 



The writer as yet has no clear vision of the gradation down- 

 ward of temperature and viscosity in the bench magma nor of 

 its transition stages downward to where bench and lake magma 

 are one. K two-phase convection in the deep region com- 

 plicated by such opposed processes as adiabatic expansion and 

 gas fluxing, or the assumptions on the one htmd of increased 

 temperature in depth from a heated substratum and, on the 

 other, of decreased temperature owing to incomplete gas reac- 

 tions, are too difficult for the student of observable facts. 

 Apparently the bench magma and the lake magma in Hale- 

 maumau, with their respective circulations, are definite facts, 

 and for the present, specalation as to what is beneath may be 

 postponed. That the lava column is a stiff body with its gases 

 in solution, and at no great depth, appears extremely probable. 



EXPEKIMEJSTS TO DeTEEMINE DIFFERENTIAL TEMPERATURES. 



Q'ueries Concerning Temperature. 



There have been hitherto presented in this paper evidences 

 from observation at Kilauea volcano of a duplex lava column, 

 of convection, of shallowness of the liquid lava lake, of heat 

 supply and of oxidation of gases. The evidence from five 

 years of recording, summarized above, necessarily leads to 

 queries, answ^erable in part, at least, by some very simple ex- 

 periments, if opportunity offer for direct contact with the lava 

 lake, grottoes and blowing cones through the agency of simple 

 instruments thrust into them. Such an opportunity of easy 

 access to the fire pit was first presented to the writer in 

 January, 1917, and for three weeks, w^hile the lava remained 

 high, a series of rough experiments was made with a view to 

 answering leading questions. 



Such questions are concerned primarily with temperature, 

 viscosity and depth. Would experiment show the lava lake 

 to be hotter or cooler below the surface crusts, than the 

 recorded temperature of about 1000° C. measured with thermo- 

 element by Ferret and Shepherd in 1911 in the '' Old Faith- 

 ful " fountain region ? Would the grottoes give temperatures 

 higher or lower than the maximum 1185° C. recorded with 

 optical pyrometer by Day and Shepherd at the time of intense 

 multiplefountainingin July, 1912 ? Is the temperature below 



