QA8 HAWAIIAN ISLANDS. 
and separated from the lake only by a dam built for the purpose. 
These waters rise from springs, as just explained. 
There have been no satisfactory observations made upon the lake, 
to ascertain whether the tides of the ocean cause an oscillation. ‘The 
author spent seven and a half hours on the ground during one day 
(from 9 a. Mm. to 4h. 30’ p. mM.) at the time just alluded to, in order to 
observe the tides. It was high tide that day on the coast at 12h. 30’. 
Between 9 a.m. and 10h. 30’ a. m., there appeared to be a fall of 
halfan inch. But after this, there were only slight irregular oscilla- 
tions, depending on the winds, and no evidence whatever of any con- 
nexion with the sea. 
Incrustations of salt were observed by Dr. Pickering, and afterwards 
by the author, high up on the bluff in the small gorge at the northwest 
corner of the basin, one hundred feet above the level of the lake, and 
half a mile distant. They occurred under a projecting ledge, and 
were an eighth of an inch thick and less. Dr. Pickering also detected 
salt plants, a species of Sesuvium, in all the three basins, the northern 
and western, as well as the Ala paakai basin; the last two are many 
feet above the level of the sea.* 
Previous to the rising of the island indicated by the elevated coral 
reef, this lake must have been many feet beneath the sea; and there 
is interesting evidence of this in a ledge of coral reef, on the southern 
ridge of the basin, at a point marked e on the topographical sketch of 
the lake region, page 245. 
Kaneohe Point.—The east point of Kaneohe 
Bay is a small peninsula, eight or nine square - 
miles in extent. HEixcepting the volcanic hills, 
the surface is nearly flat, and is formed of 
coral limestone, elevated a few feet above high 
water level. ‘There are four of these hills, of 
which three have remains of craters, more or 
less distinct. The largest of the craters, A, 
occupies the outer extremity of the peninsula. Its walls are broken 
away on the western side, exposing to view the bowl-shaped cavity 
within. It is hike Diamond Hill, except that the inner walls are more 
furrowed. The sea washes its foot, and the broken condition is owing 
to the action of its waters. The following sketches show the outline 
* Craters containing salt lakes are described by Mr. Darwin as occurring on the Gala- 
pagos.— Volcanic Islands, pp. 105, 108. 
