J. D. Dana— Volcanic Action. 109 
eal or nearly vertical projection of the materials of the broken 
bubble would follow. <A partial cooling of the lavas tends to 
increase viscidity, and this may account for the higher jets. 
The mechanism exists in Kilauea for making cinder ejections ; 
but in the case of so low jets—30 to 60 feet—the liquid mate- 
rial descends before it has had time to cool and the dropping 
masses that fall outside the lava pool plaster themselves to its 
sides. The only cinder cones are found on the slopes outside 
of the crater where greater viscidity, due to partial cooling, may - 
have existed.* 
Kilauea continues this easy, quiet throw of jets even in the 
covered chambers of the now-existing cone. Mr. Van Slyke 
speaks of the puffing up and throw of the lavas, and the swash- 
ing sounds. The work going on, producing these sounds and 
the throw, is the same as has been described—the breaking of 
bubbles of the viscid iava by the elastic vapors or gases within 
them. 
12. Fundamental forces at work in Kilauea.—In review: the 
two chief sources of upward movements are (1) the slow-acting 
ascensive force carrying the lavas to the surface, where they 
become exposed to earth-surface agencies. (2) The elastic 
force of the vapors escaping in bubbles from the exposed sur- 
face of liquid lava, producing projectile effects; these vapors 
partly of ascensive origin, but chiefly from external waters that 
become subterranean and were forced into the conduit. In addi- 
tion to the above: (8) Subterranean vapors in confined spaces 
(a) derived from the surface of the underground liquid lavas 
(those of the top of the conduit), or (8) made, gradually or 
eatastrophically, from the approach or access of waters to the 
sides of the conduit, may, by pressure, produce : 
(a) Disruptive effects, opening fissures within the crater and 
in the mountain’s sides. 
(0) Displacements or uplifts over large or small areas; and 
opening spaces for the intrusion of lavas. 
(c) When acting on a surface of liquid lava, the thrusting of 
the lava into open spaces between layers and thus producing an 
elevation of the overlying bottom of the crater and of the 
sides of boiling lakes; or into fissures, and in the latter carrying 
the lavas to heights several hundred feet above the level of the 
active vents of a crater, as in cases above mentioned, just as 
mineral oil is often thrown to heights by the confined eases 
below. 
(4) The hydrostatic pressure of the column of liquid lava 
in the crater is a common source, probably by itself, and cer- 
* In former periods pumice-like cinder ejections took place from Kilauea or its 
vicinity; but they cover a wide surface south of the crater, instead of forming 
cones. See my Report, p. 183. 
