396 PACIFIC OCEAN. 
ral features by fragmentary accumulations; and the other summits of 
the Hawaiian Group and the mountains of most Pacific islands afford 
additional illustrations, though much modified in features by degra- 
dation. The general slopes of these summits as finished by the fires, 
—or, more correctly, of the layers constituting them,—vary from one 
to fifteen degrees. 
In the molten rock, as Kilauea illustrates before the eye, there are 
all the elements requisite for producing cones of every angle. 
a. The lavas may be jetted from a vent in small ejections, gradu- 
ally diminishing; they flow only to a short distance before cooling, 
and layer added to layer by overflowings, produces a cone of twenty 
degrees or less, to forty degrees. 
b. The same lavas jetted in smaller driblets, the drops falling and 
adhering, and thus accumulating on one another, raise a very sharp 
cone, or a column, or spire of lava, (p. 178.) ‘The remarkable in- 
stance of a steep raised rim around the great lake of Kilauea, formed 
by small overflowings cooling on the edge, has been mentioned : to be 
duly appreciated, it should be remembered that this lake is actually 
a large crater, the opening fifteen hundred feet in one diameter. The 
peculiar features of the “ Old Crater” of Koloa on Kauai (p. 273), 
were probably produced by a similar mode of action.* 
c. When the overflowings are extensive, the cones that are formed 
slope at different angles, usually between one and fifteen degrees. 
The cones at Kilauea, though confined within the crater, are no tiny 
elevations, for they are sometimes a mile in diameter. They often 
become steeper above by a variation in the extent of the eruptions, 
nearly as above explained. ‘The successive ejections flowing to a less 
and less distance from the summit, thin out below, increasing the 
steepness of the cone; then larger ejections succeed, and cover the 
* From the descriptions of Cotopaxi, by Humboldt, there appears to be a circular wall 
surrounding the crater, looking like a small cylinder raised on a truncated cone; and it 
is visible to the naked eye at a distance of two miles and a half. (Personal Narrative, 
English Trans. i. 169.) It may have been produced by a boiling up of the lavas, as in 
the great lake of Kilauea, or by ejections of lava, which, on falling, still had the cohe- 
siveness of semifluidity. Mr. Darwin, who cites the above, and mentions similar facts as 
occurring at the Galapagos, (Vole. Islands, 83,) attributes the effect ‘“ to the heat or vapours 
from the crater, penetrating and hardening the sides to a nearly equal depth, and after- 
wards to the mountain being slowly acted on by the weather, which would leave the 
hardened part projecting in the form of a cylinder or circular parapet.” But the usual 
effect of volcanic vapours is to decompose, as may be seen in any solfatara and is well 
showa in the sulphur banks of Kilauea. 
