216 Jaggur — Yolcanologic Investigations at Kilaiiea. 



to start solidification. Thej would pile up on the bottom, 

 were they not disintegrated by explosion and local reheating, 

 through the union of magniatic gases with the oxygen in their 

 vesicles. As has been explained above, in view of the fact 

 that great quantities of crust have been seen foundering without 

 immediate fountaining effect, there is probably such piling up 

 along with storage of the oxygen through gas-proof glazing, 

 which coats the exterior of foundered blocks. This would be 

 especially expectable if the lake is shallow, and more viscous 

 near the bottom, in places removed from the sinkholes. 



Experiments to Determine Depth and Consistency. 

 Queries concerning Depth and Consistency. 



In order to settle this point with reference to the liquid 

 lake, shallowness being a seemingly indispensable condition to 

 account for the facts observed, an experiment was devised 

 having in view the bold project of actually sounding the lava 

 pool of Halemaumau. The preliminary work with iron pipes 

 and Soger cones had shown that the crusts are heavy and stiff, 

 the lava beueath sufficiently plastic to be dipped up in an iron 

 pot, but by no means as mobile as molten lead, while the lava 

 of the grottoes seemed much more liquid when stirred with an 

 iron pipe. The grotto lava which solidified around the pipe 

 terminal exhibited dull oxidized surfaces, smaller vesicles, finer 

 texture, and a dense selvage next the iron, while the accumula- 

 tions of normal lake lava were lustrous, lighter, glassy and 

 coarsely vesicular. The streaming currents in the lake are 

 neither strong nor deep in contact with the submerged pipes, 

 but in the grottoes they are very powerful. 



The queries suggested concerning viscosity and depth, possi- 

 bly answerable by experiment, are as follows : (1) when the 

 lake is at a high level, at what depth would a sounding rod 

 strike bottom ? (2j Is the lake magma stiffer or more liquid 

 in depth ? 



Measurement of Depth. 



On January 23, 1917, with the surface of the lava lake de- 

 pressed only 50 feet (18 meters) below the rim of Halemaumau 

 the writer tried sounding with the aid of half-inch (1*27'^"') 

 ''black iron" (steel) pipe. A total of 200 feet (60 meters) of 

 piping was screwed together and this was laid out across the 

 northeast floor adjacent to the eastern rampart of the lake 

 margin. In tiie first test Soger cones were inserted in the 

 end of the pipe nearest the lake and conflned with a screw 

 plug, but as this pipe was lost, the temperature in depth was 

 not determined by this means. The extremity of the pipe 

 remote from the lake was attached by a rope to a block and 



