246 HAWAIIAN ISLANDS. 
shows, on the left, the bluff a, fronting the lower basin; and to the 
right, part of the prominent walls of the crater c, just referred to. 
Fragments of chrysolite are sometimes found in the tufa of this 
region, half an inch in diameter, resembling the large crystals ob- 
served occasionally in some of the compact gray basalts of the mouh- 
tains. [ observed no lavas which had flowed from any of these vents. 
There is still a third basin, which is situated to the west of the first, 
near the borders of Pearl River lagoons. It is a flat plain, nearly cir- 
cular, surrounded by a low ridge, and in area about half the size of 
the last. 
These three basins occupy together a region about twelve square 
miles in extent. ‘The more northerly is about forty feet above the 
lake; and the lake was found by the Expedition to be near the level 
of the sea at half tide. 
The salt lake (called by the natives Aha paakat), when visited by 
the author, was nearly a mile wide in its longest diameter, and half a 
mile in the transverse, and occupied about half the area of the basin 
in which it lies. The shores are flat, and a rise of a foot would extend 
it to the enclosing ridge. It was formerly supposed to be fifty fathoms 
deep, but the long line prepared for sounding it descended only sixteen 
inches. ‘This was in November, 1840, at which time it was surveyed 
by officers from the Expedition. In the November of the year fol- 
lowing, when examined a second time by the writer, there were but 
siz inches of water ; and instead of finding salt only about the stones 
of the shores, or on some planted twigs, the whole bottom was covered 
with a crust of salt, averaging three inches thick and hard enough to 
support a team of horses. ‘The surface of the crust was beautifully 
crystallized, consisting of brilliant cubes, mostly a third of an inch in 
their dimensions. In some places the salt stood up in knobs, as large 
as the fist, consisting of clustered crystals; and there were columnar 
or finger-shaped aggregations, made up of a series of these large 
cubical crystals, which had formed horizontally from the knobs, or 
parallel with the surface of the water, instead of erect,—a position evi- 
