356 J. D. Dana — History of the Changes in Kilauea. 



"billows" or " hummocks," in part, of some describers, are com- 

 mon here and there over a stream and often have a height of 

 fifteen to twenty feet. I have attributed them, in my Explor- 

 ing Expedition Report, to steam made from moisture under- 

 neath. This view is sustained by the actual arching of the 

 stratum, often seen in a cross-section, and also by the cavity or 

 cavities within and the broken or fallen-in top. Some seem 

 to have been further crushed by the push of a subsequent lava 

 flow. 



The sulphur vapors may also aid in making these dome- 

 shaped elevations. And when so, the space below may have, 

 as the facts show, the roof covered with a crust and stalactites 

 of glauber salts, or with a thin crust of gypsum ; the vapors 

 having contributed material for the sulphuric acid, and the 

 labradorite of the lavas, the soda or lime. 



In many places evidence was plain that bulging had taken 

 place after the flow of the lava-stream though before complete 

 consolidation. This evidence was afforded by the tapestry 

 folds on the bulged surface, they being upside down ; that 

 is, the folds were often convex upward instead of downward, as 

 in the figure. The tapestry folds indicate the direction of 

 movement; and, when thus upside down, they prove that they 

 had been turned out of their original position. 



11. Flames from the lava-lake. — The party which made a 

 night visit to the small lava-lake in Halerna'uma'u, the evening 

 before we left the place, saw flames, similar in all respects to 

 those reported by Mr. Brigham.* They were seen to rise 

 where heavings and breakings of the lava-crust took place, and 

 not where the fires were most active. The flames were one to 

 three feet in height. They were very pale in color and slightly 

 greenish rather than bluish. I cannot claim myself to have 

 seen the flames — the rains of the evening, and a cold from a 

 thorough wetting the day before, having prevented my joining 

 the party. But critical observers were of the number — as Mr. 

 Emerson of the Government Survey, President Merritt of 

 Oahu College, Eev. S. E. Bishop and others, and the testimony 

 was unanimous. 



* This volume, pages 91, 95. 



