240 HAWAIIAN ISLANDS. 
ture, though well-formed prisms are not common. The size of the 
prisms had an obvious relation to the depth of the bed. 
A columnar structure is finely displayed in a baked tufa east of 
Diamond Hill. The bed of tufa lies beneath a layer of the black 
basaltic lava, from which the heat was derived which produced the 
change in the tufa. The texture had been rendered quite firm and 
hard, and the colour, in other parts dirt brown, is changed toa deep red. 
The prisms are very neatly regular, and mostly hexagonal; they are 
one to two inches in diameter, and three or four long. The effects of 
the heat are not apparent below six inches. 
Lateral Craters of the Eastern Division of Oahu.—The lateral or 
shore-craters have many points of interest, and merit particular de- 
scription. On the south side of the island, they form four distinct 
regions, in some of which there are several craters. Koko Head, near 
the east cape, is one of these regions:—Diamond Hill, eight miles 
west of Koko Head, along with other craters east of Honolulu, consti- 
tute a second ;—Punchboni, behind Honolulu, is a third ;—and the 
salt lake region, seven miles west of Honolulu, is a fourth. To the 
north of the Pali, there is a single district, constituting the east cape 
of Kaneohe Bay. About the Pali itself, there are indications which 
appear to deserve notice in connexion with these lateral points of 
eruption. 
Diamond Hill—Diamond Hill is one of the largest and most remark- 
able of these secondary cones. Its height varies in different parts from 
five to eight hundred feet, and it is full a mile in diameter at top. 
The bowl or crater has nearly the curve of a saucer, and is neatly 
smooth, without a loose stone to deface it. There are a few blades of 
grass about the centre, where the waters collect and remain for a while 
during the rains. 
DIAMOND HILL, AS SEEN FROM THE WEST. 
The sides are deeply gullied by the rains, or rather by rills of water 
caused by the rains; which have reduced the once smooth and gra- 
dual slopes to steep declivities, presenting, on a small scale, the 
