3508 PACIFIC OCEAN. 
The same principle is illustrated by Hale-a-kala, the eastern moun- 
tain of Maui. The last great summit eruption forms a continuous 
stream of lava from the top to the sea: it is nearly two miles wide 
where it commences at the crater, and enlarges towards the shores of 
the island. The average slope is nine and a half degrees. 
We may not, therefore, believe the statement that lavas cannot form 
beds on a steeper slope than six degrees. We cannot doubt, what- 
ever be the truth in other regions, that Mount Loa and Hale-a-kala, 
and others of similar features, have actually been formed simply by 
the process of eruption; and that the angle of declivity was fixed by 
the mode of eruption in the different phases of the volcano. 
But what may be the different phases of a volcano, and what their 
effects upon the features of the mountain? These different states 
have been pointed out; but may be here alluded to again. 
Influence of different degrees of fluidity—The lavas may have the 
fluidity of those of Kilauea, and may boil up and overflow, being too 
liquid for cinder eruptions. Whenever the heat is sufficient, this 
simple ebullition and overflow will be the common mode of action. 
In earlier conditions of our globe, this greater heat must have existed, 
and igneous centres must have been vast boiling lakes, instead of 
narrow craters, like the majority of those now active. Kilauea re- 
mains to correct our ideas with regard toigneous action, and to evince 
the important fact that cinder eruptions are, in general, a proof of sub- 
siding fires, not only in particular craters, as has been often admitted, 
but also throughout the globe. 
The most striking feature arising from these two different condi- 
tions,—the liquidity of free ebullition, and the viscidity occasioning 
cinder eruptions,—is seen in the crater of a voleanic mountain. In 
the former case, it is a deep gulf, with vertical walls of stratified rock, 
and a bottom of solid or boiling lavas. In the datter, though there may 
be a deep pit, the lava vents are surrounded by a rising cone of scoria. 
In the former, the cavity may be of vast size, for there are no limits 
to the extent of a boiling lake of lava, but such as may result from 
limited heat; and there may hence be craters of this kind, not only 
seven miles in circuit like Kilauea, or Mokua-weo-weo, but even 
three hundred or four hundred miles, like those of the moon, which 
are evidently of this character.* In the datter, the imperfect fluidity 
* See On the Volcanoes of the Moon, by the author, in the American Journal of 
Science, ii. Ser. i. 335. 
