LIFE OF JAMES DWIGHT DANA 



the hot vapors in lava-caverns, may include the recrystal- 

 lizing of basalt, therein making it into long, stony, pipe- 

 stem stalactites and stalagmites, having cavities lined 

 with transparent crystals of augite and labradorite, be- 

 sides octahedrons of magnetite. 



" It has obtained evidence, also, that the greatest of 

 eruptions may occur without the violence or the noise 

 of an earthquake, and without an increase of activity in 

 the crater; that, in place of an increase, there may be a 

 sudden extinction of the fires, all light and heat and 

 vapors disappearing as soon as the discharge begins ; of 

 the greater frequency of eruptions during the wetter 

 season of the year ; of the agency of fresh water from the 

 rains (and snows) in the supplying of steam-power for 

 volcanic action ; of the full sufficiency of water from this 

 source without help from the ocean, fresh water being 

 as good as salt for all volcanic purposes ; and, further, of 

 a great augmentation of the activity so produced with the 

 increase in altitude of the working crater. 



' These are facts from Hawaii and not all that might 

 be cited that have not yet been made out from the in- 

 vestigation of other volcanoes, not even the best known, 

 Vesuvius and Etna. 



" But much remains to be learned from the further 

 study of the Hawaiian volcanoes. Some of the points 

 requiring elucidation are the following: the work in the 

 summit-crater between its eruptions ; the rate of flow of 

 lava-streams and the extent of the tunnel-making in the 

 flow; the maximum thickness of streams; the existence 

 or not of fissures underneath a stream supplying lava; 

 the temperature of the liquid lava; the constitution of 

 the lava at the high temperatures existing beneath the 

 surface; the depth at which vesiculation begins; the kinds 

 of vapors or gases escaping from the vents or lakes ; the 

 solfataric action about the craters ; the source of the flames 

 observed within the area of a lava-lake ; the differences 

 between the lavas of the five Hawaiian volcanoes, Ki- 

 lauea, Loa, Kea, Hualalai, and Kohala; the difference in 

 kind or texture of rock between the exterior of a moun- 

 tain and its deep-seated interior or centre, for the eluci- 

 dation of which subject Kohala's northern gorges may 

 possibly afford material ; the difference between Loa, Kea, 

 and Haleakala in the existence below of hollow chambers 



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