268 HAWATIAN ISLANDS. 
‘there are also compact layers, without a trace of a cell. Some of 
the boulders, in the Hanapepe Valley, consisted of grayish-blue 
basalt, containing crystals of chrysolite an inch or more in their 
several dimensions. The clinkstone varieties were not met with in 
the course of our rapid jaunt over the island. 
The conglomerates are very various in structure. Some are a 
coarse tufa; others consist of large, rounded masses, many thirty cubic 
feet in size, lying together, with earth and pebbles filling the inter- 
stices. They contain all the rocks of the mountains, the most cellular 
as well as the compact. Near the descent into the Hanapepe Valley, 
not far from the bottom, there were masses of scoria in the conglome- 
rate, looking as if there had been ejections of scoria in the vicinity 
while the island structure was in progress, and before the superin- 
cumbent two hundred feet of layers had been formed. 
There is often a tendency to prismatic structure in the basaltic 
rocks, and distinct columns were occasionally met with. ‘Towards 
the interior of the island, the prisms are most perfect and extensive. 
At the falls of the Hanapepe, they were well defined, and could be 
traced for a height of one hundred and twenty feet, though less dis- 
tinct below; and above, they were a little curved on each side of the 
falling water, so that, if continued, they would span it with a Gothic 
arch. On the side of the valley opposite the fall, the steep sides of 
the slender peak overhanging the valley, show a columnar structure. 
This structure was met with, in many places in this valley, before 
reaching the falls: but we observed no examples of much interest 
near the bottom of the gorge, and could see only at a distance the 
columns which occur in the inaccessible heights above. In some thin 
layers, the columns were but six feet long, and ten inches in diameter. 
Where we first reached the bottom on the descent, we left a high pre- 
cipice on our right, which was distinctly columnar throughout its 
upper half: the following section was there presented. 
Eighty feet coarse basalt, with a columnar structure, the upper 
thirty feet imperfectly so; columns irregularly curved in some parts. 
Twenty-five feet ;—a second layer, but not distinctly columnar. 
Twenty feet ;—a third layer, not columnar. 
Twenty feet, or to the bottom; coarse conglomerate. 
The layers of basaltic lava were black and ragged. The conglome- 
rate is the same bed which has been described as containing scoria 
and light cellular lava. The place was, probably, a lateral vent at 
some period in the history of the island. 
