WATER AND VOLCANIC ACTIVITY DAY AND SHEPHEKD. 297 



carbon dioxide, sulphur dioxide, and sulphur trioxide. Only at the 

 automobile road terminus 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 

 eases small amounts of SOajbut more frequently exhale merely steam. 

 Thus in caves where stalactites are forming at a temperature of about 

 40°,' the gas present was in all cases examined merely air and steam 

 and contained no more COo than is normally contained in the air. 

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

 formation of gelatinous silica in the presence of some kind of gi-een 

 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 SO,, SO3, and free sulphur, together 

 with steam ; which ingredient predominates is of no particular in- 

 terest, 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 rela- 

 tively 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 

 amount of chlorine given off by the crater at the time of our studies 

 was relatively insignificant, it seemed worth while to look for it, as 

 Brun had done, in the older lava which had been exposed to the 

 fumes of the crater for several years. A specimen of lava was ac- 

 cordingly 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-gi*am 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 exhalation of the volcano is SO^, 



1 W. T. Brigh.im : " The volcanoes of Kilauea and Mauna Loa on the Island of Hawaii," 

 p. 29. Honolulu, 1909. 



