J. D. Dana — History of the Changes in Kilauea. 217 



who refers part of the movements in the lake to escaping atmos- 

 pheric air ; the air being supposed to be carried down by the 

 splashing and jetting lavas, there to become the source of the 

 splashing ; and to become confined in this and other ways, and 

 be carried deeper for other work.* But the amount of vapor 

 escaping from a lake in times of moderate activity, when it is 

 mostly crusted over, is very small — being only that from the 

 vesicles (p. 194) and breaking bubbles in the actively liquid 

 portion ; and in a state of brilliant action, the hot air above, up 

 to a height where the temperature is diminished from that of 

 the liquid lavas to 300° F. will dissolve and hold"invisible nearly 

 o times as much moisture as at 212° ; up to 410°, 16 times as 

 much: and to 446°, 27 times. The absence of vapors over a 

 flowing lava stream is made evidence against the presence of 

 water ; but if all is from one source, there should he none except 

 at the source (ibid.) 



The amount of sulphur in the vapors, and its condition be- 

 fore the escape from the lava, whether as sulphur vapor sim- 

 ply or as sulphurous acid (sulphur dioxide), are questions for 

 the future investigator. Pyrite, or some iron sulphide, being 

 its probable source, I add that I have detected pyrite in the 

 lava of a dike on Oahu, but not in the lavas of the crater, where 

 we should hardly expect its presence. Chalcopyrite (copper 

 pyrites) may also be present ; for, in 1840, I found, at the 

 southwestern sulphur banks, some blue copper sulphate, f 

 The faintly greenish tint of the flames which have been seen 

 (xxxiv, 24, 356) may have this source. 



Carbonic acid has not been observed escaping from fuma- 

 roles about any part of the Hawaiian Islands, and no frag- 

 ments of limestone have been found among the ejectamenta 

 of Kilauea or Mt. Loa The volcanoes stand in the deep ocean, 

 and the conduit must come up through old lavas for thousands 

 of feet, and hence carbonic acid is only a possible not a proba- 

 ble product. The position of the volcanic region in mid- 

 ocean, where continental geological work has, most probably, 

 never gone forward, makes it questionable whether limestone 

 is passed through by the hot lavas at any depth. 



The presence of hydrogen among the escaping vapors re- 

 mains to be determined. The pale, hardly bluish flames seen 

 about the Great Lake may come from the burning of escaping 

 hydrogen, or of sulphur vapor, or of hydrogen sulphide. 



The source of the water or moisture, whence comes the chief 

 part of the escaping vapors, is probably atmospheric. On this 

 point the arguments appear to be as strong now as in L840. 



* Vestiges of the Molten Globe, Part II, 8vo, Honolulu, 1887. 



f My Exped. Report, pp. 180, 201, 2u2, the last containing an analysis. 



