METHOD OF COLLECTING VOLCANO GASES 583 



had found. These tubes were of the same capacity as the individual 

 tubes in the previous experiment (one-half liter), but were provided with 

 a long stem, on the remote end of which was blown a thin glass bulb. 

 The plan was to attach these tubes to a pole of convenient length and to 

 thrust the end carrying the thin bulb into the dome, where the heat might 

 be expected to explode the thin glass immediately, permitting the tube to 

 fill, with the gases, and as quickly to seal it again by melting down the 

 broken end. The tubes were dried in contact with phosphorus anhydride 

 and the degree of exhaustion checked by electrical discharge tests from a 

 small static machine. When a number of these tubes had been prepared 

 and everything was ready for a second attempt, the top of the lava dome 

 had fallen in, and the liquid lava in the basin had gone down to such an 

 extent that it offered no further opportunity to collect gases under condi- 

 tions which should assure original gas without contamination from the 

 air or otherwise. In fact no other opportunity offered until December 4. 9 



The second Attempt to collect Gases 



On December 4, with the lava surface 360 feet below the rim, and 

 therefore even less conveniently accessible than on the previous occasion, 

 a similar dome formed directly on the border of the lava lake, and the 

 second attempt was made to collect a quantity of gas — this time in the 

 vacuum tubes. In order that there might be no possible doubt about the 

 excess gas pressure within the lava dome, the descent into the crater was 

 made at night, when the pale blue flame of the escaping gases could be 

 plainly seen emerging from the crack in the dome. The manner of col- 

 lecting the gases was exactly that which was planned and described above, 

 and six tubes were filled with gas under these conditions. 



On descending into the crater to collect gases from the December dome, 

 it was found that in addition to a long slit or crack across the top, from 

 which the gases were discharging constantly, there was a second opening 

 near the base which was not noticed before the descent, but which gave 

 access to air at the base of the dome and thus behaved like an air blast in 

 a furnace. The gases were therefore partly burned within the dome in- 

 stead of outside, and the tubes, which were filled at the upper opening, 

 were accordingly found to contain chiefly burned gases — that is, the free 

 hydrogen had become water, the free sulphur had burned to S0 2 , the CO 

 appeared as C0 2 , etcetera. 



8 In the meantime one of the authors (Day) was obliged to return to Washington, 

 leaving the other (Shepherd) to finish the task alone. 



