106 J. D. Dana— Volcanic Action. 
are generally small unless open active vents exist along such 
fissures.* 
8. Projectile action.—In. Kilauea, in 1841, the projectile action 
of the lava-pools, consisted in the throw of jets of lava toa 
height of 80 to 60 feet over the whole liquid surface—many 
rising and falling simultaneously. I watched the process for 
some time while within four or five feet of one of the smaller 
lakes, and, also, but necessarily from a much greater distance, 
the more brilliant display over the great lake of Halema’uma’u. 
This lake, owing to contact with the air above had usually a 
red-hot surface (except when blackened at times in patt by in- 
cipient cooling) ; but in the play ofjets over its wide surface, lines 
of white heat, or very nearly white, opened to view between 
them, which acompanion in the expedition, Dr. C. Pickering, 
well compared to a net-work of lightning flashes. _ . 
The jets were ordinarily 30 to 60 feet high; in one of- the 
small pools about 30 feet, but 50 to 60 at intervals. At times 
of lull they ceased or nearly so. The diameter, if I remember 
rightly, was three to six inches. With a mean of 4 inchesanda 
height of 30 feet, each would have contained about 400 pounds 
of lava, making the force expended equivalent to that required 
to raise 400 pounds 10 or 12 feet. They were in form, in rise 
and fall, and apparently in mode of projection, like the little 
jets over a surface of boiling water; and the word edullition 
seemed to all appearance to express what was going on. On 
other occasions jets have been seen of 100 to 200 feet, and also 
of five or six feet and less. In the~higher jets the lava is usu- 
ally broken into parts, and the lowest of two or three feet are 
sometimes broad and hemispherical. 
The boiling movement has been recognized by all who have 
visited the crater. Rev. Wm. Ellis, of Kilauea, in August, 
1828, describes a lake as a flood of fire in ‘‘ terrific ebullition ;” . 
and Capt. John Shepherd, R. N., there in 1839, speaks of the 
“violent ebullition” as ‘‘caused by the escape of elastic fluids 
which threw up the spray [jets] in many parts 30 to 40 feet.” 
In the case of “ blow-holes” the boiling process goes on 
beneath a small aperture in the solid lavas, and the liquid rock 
is thrown up in masses or driblets, with swashing sounds, and 
volumes of vapor at each throw. Small, steep cones of lava 
are made around the hole; and one such, surmounted by a 
column consisting of adhering lava drops (each 4 to 5 inches 
across), the whole 40 feet high, is figured in my Report, and the 
* Prof. J. Prestwich discusses the subject of the agency of water in volcanic 
action at much length in a valuable memoir read before the Royal Society, in 
1886. He makes no use of the facts afforded by Kilauea or of the bearing of the 
phenomena there observed on the great subject of voleanic action. As the views 
here given on the agency of water, and the special methods of its action are 
those of 1849, I have no occasion to make further mention of Prof. Prestwich’s 
paper. 
