598 DAY AND SHEPHERD WATER AND VOLCANIC ACTIVITY 



amount of chlorine given off by the crater at the time of out studies was 

 relatively insignificant, it seemed worth while to look for it, as Brim had 

 done, in the older lava which had been exposed to the fumes of the crater 

 for several years. A specimen of lava was accordingly taken on the lee 

 side of the crater rim, where it had been fumed with the gases carried 

 over it by the trade-winds for 20 years or more. This lava in a 2-gram 

 sample yielded no test for chlorine. This result is not as satisfactory as 

 it might otherwise be from the fact that the major portion of the exhala- 

 tion of the volcano is S0 2 , which when combined with water readily 

 changes to sulphuric acid and would tend to drive the chlorine out of 

 any combinations which it might form. It constitutes, nevertheless, a 

 plain indication that the amount of chlorine actually evolved is insig- 

 nificant. 



Discussion of Kesuets 



general conclusions 



In so far, then, as this reconnaissance yields final results, it shows that 

 the gases evolved from the hot lava at the Halemaumau crater are N 2 , 

 R 2 0, C0 2 , CO, S0 2 , free H, and free S, with CI, F, and perhaps NH 3 , 

 in comparatively insignificant quantity. Xo argon or other rare gases 

 and no hydrocarbons were found. 



THE EFFECT OF THE REACTIONS BETWEEN THE GASES 



The first plain conclusion which follows from the discovery of this 

 particular group of gases associated together at a temperature of 1,000° 

 or more is that they can not possibly be in equilibrium there, and that 

 chemical action between them is still going on. Whatever may have been 

 the previous opportunities for chemical readjustment among the gases as 

 they rose in solution with the magma and were gradually set free with 

 the diminishing pressure, they are still in process of active reaction when 

 discharged into the air. Free sulphur, for example, could not have re- 

 mained in permanently stable association with C0 2 ; neither could free 

 hydrogen be found in stable association with C0 2 and SO, at 1,000°. 



THE EFFECT OF THE EXPANSION OF THE GASES 



Moreover, as the pressure continued to diminish during the progress of 

 the upward movement, the quantity of gas released from solution, and 

 therefore free to enter into new relations, must have been constantly and 

 rapidly increasing up to the moment of discharge into the an 



Two consequences follow from the continuation of this operation, 

 which are thermally opposite in sense. First is the rapid expansion of 

 the gases with the release of pressure, which is a cooling phenomenon, and 



