Iyneous Ejections, Volcanoes. 115 
usually solid throughout, without the minutest vesicle, and 
similar complete compactness characterizes many fissure ejec- 
tions even of volcanic regions, when they have taken place at a 
considerable distance from the volcanic vent.* This would 
want of sympathy between the summit crater of Mauna Loa, 
nearly 14,000 feet in elevation, and the larger crater of Kilauea 
on the flanks of the same broad mountain only 4000 feet above 
the sea, I have adduced as evidence that the ordinary volcanic 
action was here due to movements in the of the 
lava columns, probably to portions extending little below the 
sea-level, and that these voleanoes were therefore mainly de- 
pendent for their various phases on the freshwaters precipitated 
ever the mountain slopes. The waters of the ocean take their 
part in such action; but they are not in Hawaii the chief source 
of activity.+ The effects of hydrostatic pressure have been ex- 
emplified in the same volcanic mountain, not only in fractures 
of the mountain, but also in majestic fire-fountains, in which 
the lavas were thrown to heights from 100 to 700 feet.t 
other Part, on the formation of the Continental plateaus 
and Oceanic depression, will finish this memoir. 
*Itisa i volcanic ejections are 
lags or scorn,” The eariace of onto ie ofteuof this character fora depth of 
aura or perhaps a foot. But below this, the layer is beste a a peed a 
of the rock is as told aad fine from vosiclesas the dolerite of the Connecticut 
o 
. 
+ See further o th ints the author’ ll. . Geol. Report, and also 
4 . m these es tng amet sadly often rete a to, has 
vari 
excellent observations on this subject, as on oth 
} This Journal, II, xiv, 219, 254, 1852. 
