OAHU. 257 
In Hawaii, as has been shown, we have an instance of an island 
formed by the action of three great vents or centres of eruption, Kea, 
Loa, and Hualalai. From the features of Maui, it is as evident that 
the origin of this island must be attributed to two centres of eruption, 
its two insulated peaks standing apart, and coalescent only at base, 
like the two great summits of Hawaii. What then follows for Oahu? 
Is not this double-headed island another example of the conjoined 
eruptions of two vents, one the eastern, and the other, the western? 
The rocks of the two parts have flowed from distinct openings, for 
they both slope gently towards the dividing plain, precisely as on 
Maui and Hawaii. In the eastern division, the inclination of the 
layers follows the points of the compass, the southern side sloping 
south, the southwestern, southwest, the western, west, exactly as with 
Mount Loa. Although the inclination is much obscured by the many 
valleys, we may distinguish a sloping plain along the tops of the 
ridges which rise from the coast, and from ridge to ridge it is so even 
in its height, and the layers composing them are so regular and uni- 
form, that we cannot doubt the whole to have been continuous, and 
subordinated to a single elevation of volcanic origin. On the side of 
the dividing plain, we may distinctly follow this sloping surface up 
the declivities, see it become more and more cut up by valleys, yet 
retaining a uniform angle of declivity. 
It is reasonable to infer that the beds of lava, (which must have 
flowed from some direction,) have flowed from that towards which 
they rise: and when we find them all pointing upward towards a 
single central area, can we hesitate with regard to their origin, any 
more than we can with reference to the lavas over the dome, Mount 
Loa? The inclination of the layers is small—only three to ten de- 
grees, and the flowing of lavas, at such inclinations, is abundantly 
exemplified among the forming cones of Hawai. ‘There are no up- 
turnings of strata, no irregular tiltings in any part of the island; the 
only tilt, is this gentle slope away from a central area. 
These remarks with regard to the nature of the eastern division, 
apply also to the western range. The only difference is, that, in the 
latter, the original slopes have been more completely obliterated by 
valleys, and both the heights and declivities are more irregular. 
It is obvious, therefore, that Oahu, although now consisting of two 
nearly straight and narrow ranges of mountains, one thirty, and the 
other fifteen miles long, must, at some former period, have been a 
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