TAHITI. 299 
taining much iron become at once deep red. ‘The crystals of augite 
next yield, becoming at first crumbling, and then assuming a dark- 
brownish colour. 
The soil produced by decomposition varies in colour from a dirt 
brown, through yellow and brownish shades, to a brick red or brown- 
ish red. Many of the hills are entirely of the latter colour, but a 
brownish yellow appears to be most common. On the summit of 
Mount Aorai, the colour was found to vary from brownish yellow to 
deep red, and in most places, the surface for ten to twelve inches was 
as black as vegetable mould. 
The red soil often makes a good red ochre, and is used as a paint 
by the natives. 
2. EVIDENCES OF CHANGE OF LEVEL. 
One of the objects I had in view when commencing the ascent of 
Mount Aorai, was an examination of the reputed coral bed, located, 
according to report, on the summits of the Tahitian mountains. 
There was scarcely a native, but had heard of the mountain coral and 
the screw shells; yet it was difficult to find one who had ever seen 
either. We were at last successful, and started with the assurance 
from our guide that he had seen both, and would lead us to the spot. 
On approaching the summit, the valleys were searched for frag- 
ments, but none were found. Having reached the top, we looked 
around for the bed, but there was nothing in sight on the surface. 
My guide commenced digging and I joined him. Soon he brought 
me a coral fragment, a grayish white trachytic variety of the basalt. 
When told that it was not coral, he insisted that it was coral in Tahiti. 
We dug still longer and searched around, but it was all unavailing. 
The screw shells he could not find. ‘They were of the same nature, 
he said, but longer and round. My guide had explained to me 
on the ascent that they were worn smooth like the stones, yet I 
scarcely expected so close a resemblance. In some places the ridge 
was bare, but without any trace of coral. 
The peak of Orohena, as it is higher than Aorai, may possibly have 
its coral bank. Yet we believe that there is no evidence of it what- 
ever. ‘The view from Aorai showed no signs of it: and the examina- 
tion of the valleys of the island by the officers of the squadron in 
