244 J. D. Dana on Volcanic action at Mauna Loa. 
tains at heights of 10,000 to 14,000 feet, when Kilauea on the 
flanks of the same mountain 6000 to 10,000 feet below, hold its 
capacious gulf wide open, and heedless, keeps on its boilings and 
mutterings. A syphon with the fiuid lava standing in one leg 
10,000 feet higher than the other, and yet without sympathy be- 
tween the two—the upper at times even playing a jet of 1000 
feet diameter and many hundred feet high,—is a strange problem 
for the geologist. Deny the connection,—and the hypothesis of 
a communication now existing betwen a modern volcano and 
the earth’s interior fires has but a poor foundation. Admit the 
connection,—and a mystery remains to be solved. 
e may say that a connection exists; and that, as the craters 
are twenty miles apart, the junction may be at least 100 or 150 
miles below ; so that the friction or resistance to free motion In 
the long conduit isnot more than counterbalanced by 10,000 feet 
in height of lava.—Or, we may suppose, as the writer suggests 
in his Report, that as the aetion causing the eruptions 1s com- 
paratively superficial or within a depth of a few miles, it being 
in fact, a rising from developed vapor, as a vessel of fermenting 
syrup froths over, (as suggested by C. Prevost,) such an action, 
a kind of inflation, does not necessarily increase much the weight 
of the column compared with that of its whole length. 
Both causes may indeed operate. Still, supposing the lava col- 
umn of the central crater two miles in diameter at top and that 
of Kilauea three miles, these being the diameters of the craters, 
we should naturally infer that the heat and the diameter would 
increase downward rather than decrease ; and that the passage 0 
the syphon would therefore be free. Yet the law of latent heat, 
by which much more heat is required to produce fusion than the 
setisible heat of the fused material, makes it possible that @ 
melted mass may be held within a basin made of the same mate- 
rial unmelted, as water in a basin of ice; and it also increases 
the facility with which the melted mass, be it even the conduit 
of a volcano, would be encroached upon by the cold rock, the 
latter congealing it by conduction. 
This great question may therefore be regarded as still unset- 
tiled. If the thickness of the earth’s crust be but thirty myes, 
as has been sustained on good grounds, it exceeds only one*na! 
the distance between the summit crater of M. Loa and Kilauea; 
and in that case a connection of the two conduits could hardly 
take place at all except through the central fluid mass of the 
globe; for to bring them together within twenty miles of the 
surface would require a rapidity of convergence between them, 
which, although possible, cannot be deemed probable. 
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