ae 
alia: clit ia a a 
ee ee ee 
a 
J. D. Dana on Denudation in the Pacific. 49 
II. Valleys of the third kind have an extensive plain at bottom 
quite unlike the strip of land just described. They sometimes 
abut at head against vertical walls, but oftener terminate in a 
wide break in the mountains. 
The ridges of land which intervene between the valleys, have 
a flat or barely undulated surface, where these valleys intersect 
the lower plains or slopes; but in the mountains, they are narrow 
at top, and sumetimes scarcely passable along their knife-edge 
summits. Some of them as they extend inward, become more 
and more narrow, and terminate in a thin wall, which runs up 
to the central peaks. Others stop short of these central peaks, 
and the valleys either side consequently coalesce at their head, 
or are separated only by a low wall, into which the before lofty 
ridge had dwindled. The crest is often jagged, or rises in sharp 
serratures. 
The main valleys, which we have more particularly alluded to 
above, have their subordinate branches ; and so the ridges in ne- 
cessary correspondence, have their subordinate spurs. 
As examples of the valleys and ridges here described, we intro- 
duce a brief account of an excursion in the Hanapepe valley on 
Kauai, one of the Hawaiian Islands, and a second up the moun- 
tains of Tahiti. 
Hunapepe Valley, Kauai—We reached its enclosing walls, 
about four miles from the sea, where the sloping plain of the 
Coast was jist losing its smooth, undulating surface, and changing 
into the broken and wooded declivities of the interior. The val- 
ley, which had been a channel through the grassy plain, a few 
hundred feet in depth, was becoming a narrow defile through the 
mountains. A strip of land lay below, between the rocky walls, 
Covered with deep-green garden-like patches of taro, through 
which a small stream was hastening on to the sea. 
We found a place of descent, and three hundred feet down, 
reached the banks of the stream, along which we pursued our 
course. The mountains, as we proceeded, closed rapidly upon 
Us, and we were soon in a narrow gorge, between walls one thou- 
sand feet in height, and with a mere line of sky over head. ‘The 
Stream dashed along by us, now on this side of the green strip of 
land, and then on that ; occasionally compelling us to climb up, 
and cling among the crevices of the walls to avoid its waters, 
Where too deep or rapid to be conveniently forded. Its bed was 
often rocky, but there was no slope of debris at the base of the 
Walls on either side, and for the greater part of the distance it was 
ered by plantations of taro. ‘The style of mountain archi- 
tecture, observed on the island of Oahu, was exhibited in this 
ded defile on a still grander scale. The mural surfaces en- 
closing it had been wrought, in some places, into a series of semi- 
Seconp Srrms, Vol, IX, No. 25, J n., 1850. 7 
