WATER AND VOLCANIC ACTIVITY- — DAV AND SHEPHERD. 2 M 



review is not altogether easy. His reasoning is based on deductions 

 from many phenomena, such as apfteal to an observer on the ground; 

 great lava streams without a trace of vapor rising from them; a 

 condition of great activity in the lava pit of Halemaumau (the only 

 portion of the Kilauea Volcano now continuously active), with 

 hardly a trace of any cloud above it; a rather conspicuous difference 

 in character between the Halemaumau cloud (when there is one) 

 and the clouds which arise from numerous steam cracks in the coun- 

 try round about, etc. Perhaps the chief factor which clinched his 

 conclusion was the fact (which we also observed) that there are 

 times when a magnificent cloud rises from the active basin, separated 

 by but a day or two from periods when practically no cloud can be 

 seen, and this with no apparent change either in the character or 

 amount of activity visible in the basin. He therefore concluded 

 that if steam was the moving force, and if the gi'eat white cloud was 

 the manifestation of that fact, its presence must be expected on one 

 day- as much as on another in which the same gas and lava condi- 

 tions appeared to prevail. 



He was also able to discover no diminution in the liquidity of the 

 'lava, either in the crater or in the great lava streams during those 

 periods when no cloud was seen, and therefore no casual connection 

 between the presence of the gases and fluidity of the lava. 



Had it occurred to Green to try to remelt some of the solidified 

 lava after the gases had escaped, this last puzzling question would 

 have been clearer to him, for the crudest effort would at once have 

 revealed the fact, which since then has often been noted, that these 

 lavas, Avhen reheated to the temperature prevailing in the lava lake 

 l)efore solidification, remain quite rigid — the characteristic fluidity 

 has departed with the escaping gases. 



Brun's statement of his observations at Kilauea is more explicit. 

 In particular he offers six definite reasons for believing that steam is 

 not present either in the lava basin or in the cloud above it. They 

 are these : 



(1) The cloud arising from the crater does not evaporate in the 

 sun as do the clouds arising from neighboring cracks after a rain, 

 but can be seen floating majestically away often for 20 miles or more. 



(2) No rainbow or other optical phenomena can be detected in the 

 cloud arising from the crater, although rainbows are abundant 

 enough in the vicinity under appropriate conditions. 



(3) If the cloud were of steam emerging from white-hot lava, 

 there should be an interval of a few feet between the point of emer- 

 gence and the beginning of condensation (like the dark space imme- 

 diately in front of the spout of a steaming teakettle) in which the 

 steam should be invisible. No such dark space could be seen. 



