ANALYSES OF GASES 597 



The water condensed in a tube filled by pumping at this point yielded 

 about 3 milligrams of chlorine, but no fluorine. 



With regard to the chemical products along this circular crack about 

 the crater basin of Halemaumau, we can sum up by saying that water, 

 although no doubt partly of meteoric origin, was always present at the 

 time of our visit, and the gases were prevailingly high in carbon dioxide, 

 sulphur dioxide, and sulphur trioxide. Only at the automobile road ter- 

 minus was chlorine found to be present in an amount sufficient to show 

 appreciably in a field test. 



Cracks farther removed from the Halemaumau pit show in some cases 

 small amounts of S0 2 , but more frequently exhale merely steam. Thus 

 in caves where stalactites are forming at a temperature of about 40 °, 17 

 the gas present was in all the cases examined merely air and steam and 

 contained no more C0 2 than is normally contained in the air. The for- 

 mation of the stalactites in this cave is accompanied by the formation of 

 gelatinous silica in the presence of some kind of green algae. As might 

 be expected, neither carbon monoxide nor hydrogen was detected in the 

 gases taken from these cracks. 



Sublimation and Decomposition Products 



Numerous samples of decomposed lava were taken from various points 

 around the crater where the alteration of the surface lava is conspicuous. 

 While the examination of these is not complete, the preliminary results 

 can be summed up by saying that the samples consist primarily of the 

 products to be expected from a sulphuric acid decomposition of the usual 

 basic lava. In most of the places where these samples were gathered the 

 surface is constantly bathed by the volcanic cloud carrying S0 2 , S0 3 , and 

 free sulphur, together with steam; which ingredient predominates is of 

 no particular interest, so far as the general problem of surface alteration 

 is concerned. In addition to the gaseous products, the breaking down of 

 the lava results in ferric sulphate, which is formed more or less rapidly 

 from the oxide in presence of steam. Alum occurs at favorable places 

 over most of the main floor of the Kilauea crater, but the amount is 

 relatively small. Gypsum is perhaps the most common decomposition 

 product which is left, and this occurs all over the crater. Projecting lava 

 points on the under side of a lava block will often be found tipped with 

 small crystals of gypsum. 



Since the gases collected point uniformly to the conclusion that the 



17 W. T. Brlgham : "The Volcanoes of Kilauea and Mauna Loa on the Island of 

 Hawaii," p. 29. Honolulu, 1909. 



