424 REPORT OF NATIONAL MUSEUM, 1904. 



Assuredly, if, while Kilauea is open on the Hanks of Mount Loa — a vast gulf :'.', 

 miles in diameter — lavas still rise and are poured out, Kilauea is do safety valve 

 even to the area covered by this single mountain alone. 



The conclusions based upon the .study of these Hawaiian volcanoes 

 were to the effect that: 



1. The majority of the Pacific volcanic summits were formed from 

 successive eruptions of molten rock, alternating sometimes with cinder 

 or fragmentary ejections. 



2. That the eruptions are, in general, the result of a rising or ascent 

 of the lavas, owing to the inflation by heat of such vaporizable sub- 

 stances as sulphur and water, the overflow or lateral outbreak taking 

 place in consequence of the increased pressure from gravity and from 

 the elasticity of the confined vapors, the contraction of the earth's sur- 

 face being no more necessary for an eruption than the contraction of 

 the sides of a pot of water to make it boil. 



lie concluded further that volcanic action usually proceeded from 

 fresh water gaining access to a branch belonging to some particular 

 outlet or vent, and not to a common channel at greater depth. The 

 lack of sympathetic action between two neighboring vents was thus 

 explained on the ground that the union of their channels ""took place 

 far below the level to which the waters that ordinarily feed the tires 

 gain access." 



To the elevation theories of volcanic craters advocated by Von Buch 

 he took exception, as he did also to the theory of Bischoff, who 

 appealed to the internal igneous fluids for the source of volcanic action. 



The highly feldspathic, coarsely crystalline, and solid centers of 

 certain volcanic mountains, in contrast with the more vesicular and loss 

 dense outer portions, he rightly ascribed to slowness in cooling, the 

 central mass being protected on all sides from the external air. Inci- 

 dental^ he discussed a problem which has become known to modern 

 petrographers as that of magmatic differentiation. He argued that, 

 given a large crater like that of Kilauea, the rise of the lavas through 

 the center would be accompanied hy a descending current along the 

 side, though of less distinctness. The essential constituents of a rock, 

 for example, being augite and feldspar, wherever the temperature of 

 the liquid mass becomes sufficiently lowered, there the feldspar will 

 commence to solidify or will slowly stiffen in the midst of the fluid 

 material made up of the other ingredients. Under these conditions 

 the ascending vapors would urge the feldspar upward much less freely 

 than the more liquid part of the lava, for the latter would } T ield more 

 readily to the inflating vapors and thus become lighter and rise to the 

 surface. This process, going on throughout the whole progress of 

 the cone, would keep the center feldspathic below a short distance 

 from the summit. The residue from the feldspathic crystallization, 

 consisting of ferruginous silicates, would be brought upward in the 



