KAUAI, 267 
1. Structure of Central Kauai and the Shore Plains subordinate. 
As far towards the interior as the island was examined by the 
author, it consisted of a series of layers, like the mountains of Oahu. 
We have already alluded to the regularity of stratification presented 
in the valley sections of the shore plain, and have stated farther that 
the same structure continues to characterize the walls of the gorges 
beyond this plain. The layers are remarkably regular in direction, 
and dip with the slope of the plain, at an angle of one to five degrees ; 
they are so nearly horizontal, that the inclination is often hardly 
apparent. 
The dip, as in Oahu, corresponds in direction with the points of the 
compass, the surface rising gradually towards the interior from the 
southern, eastern, and northern shores. 
The layers differ much in thickness, and enlarge as we approach 
the interior. Within five miles of the sea, they vary from ten to one 
hundred feet: twenty to twenty-five feet is the average thickness 
Each layer stands out distinct on the bluff, owing either to decompo- 
sition or removal between, or to open spaces left by the flowing rock. 
The under surface of the layers is frequently very jagged, and some 
small caverns or deep cavities may be seen among its protuberant 
points. 
These layers consist of the same compact and conglomerate rocks 
which have been described in the account of Oahu and the other 
islands. 
They often have the appearance of a recent lava, though generally 
nearly compact, with irregular cells. Some grayish layers are very 
cellular, though not scoriaceous; the under surface of many layers, 
as just stated, strikingly resembles the recent formations of Hawai. 
The rock is usually of a grayish-black or grayish-blue colour, with a 
slightly glistening lustre when broken: some ferruginous varieties are 
black and heavy. Grains of chrysolite are commonly disseminated 
through the texture, and, among the glistening points, particles of 
magnetic iron may sometimes be detected. Other than this, it is rare 
to find imbedded crystals in the rock, or any trace of crystallization. 
Porphyritic varieties are, however, met with: in those seen, the feld- 
spathic crystals were small and imperfect. Augite is seldom found in 
distinct forms. 
Though generally somewhat cellular within five miles of the coast, 
