OAHU. 237 
to their head. Of this character is the Nuuanu Valley, back of Hono- 
lulu; and another a few miles farther west is said to be similar. 
Still another kind of valley occurs where the general surface of the 
country is nearly level, as in the dividing plain of the island, or where 
the slopes are very gradual. They are deep channels cut out of the 
rocks, with vertical walls of two to four hundred feet, and a narrow 
riband of land at bottom through which the stream takes a serpentine 
course. 
The ridges separating the valleys have broad flat slopes where they 
first rise from the shore plain, or after the first one or two hundred feet 
of ascent; but beyond, they become narrow and irregular. Many 
terminate in a thin ridge running up to the crest; others break off 
abruptly before reaching it, and precipitous depths of great extent 
intervene. The sides of these ridges are occasionally abrupt and lofty, 
and some portions appear as if formed of rounded buttresses or clus- 
tered columns, constituting a sublime style of mountain architecture. 
Just west of Kaneohe Bay there is a spur of this kind, fifteen hundred 
feet in height. It stands by itself like a temple cut-from the hills, 
and we look almost unconsciously for an entrance to the solemn gran- 
deur of its interior. 
A remarkable feature of the country gradually opens to view, as the 
voyager approaches the shores of Oahu. Besides the hills and valleys 
of the interior, there are at several places along the coast isolated ele- 
vations of a broad conical shape. ‘They have an earthy stratified ap- 
pearance, and are much gullied down the slopes. In certain views, a 
glimpse is obtained of a large cup-shaped cavity at top. These are 
tufa craters, singularly fresh in their appearance, although they have 
evidently been long extinct. Some of them form the prominent capes 
of the island. One of these tufa craters stands against the side of 
the hills, just back of Honolulu, significantly called the Punch- 
bowl: it is a capacious bowl, five hundred feet in height. Diamond 
Hill is another, still larger, forming the southernmost point of the 
island. At Koko Head, near Makapuu Point, and east of Kaneohe 
Bay, are similar subordinate cones. 
60 
