78 CORAL FORMATIONS. 
ashes are sometimes distributed over these islands, through the atmo- 
sphere; and in this manner the soil of the Tonga Islands is improved, 
and in some places it has received a reddish colour. 
The officers of the Vincennes observed several large masses of com- 
pact and cellular basalt on Rose Island, a few degrees east of Samoa: 
they lie two hundred yards inside of the line of breakers. The island 
is uninhabited, and the origin of the stones is doubtful; they may 
have been brought there by roots of trees, or perhaps by some canoe. 
Notwithstanding the great number of coral islands in the Paumotu 
Archipelago, the botanist finds there, as Dr. Pickering informs me, 
only twenty-eight or twenty-nine native species of plants. The fol- 
lowing are the most common of them :— 
Portulacca, two species. Pemphis acidula. 
Sceevola Konigii. Guettarda speciosa. 
Pisonia? one species. Triumphetta procumbens. 
Tournefortia sericea. Suriana maritima, 
Pandanus odoratissimus. Convolvulus, one species, 
Lepidium, one species. Urtica, one or two species. 
Euphorbia, one species. Asplenium nidus. 
Morinda citrifolia. Achyranthus, one species. 
Boerhavia, two species. A species of grass. 
Cassytha, one species. One or two rubiaceous shrubs, 
Heliotropium prostratum. Polypodium, 
On Rose Island Dr. Pickering found only the Pzsonza and a Portu- 
lacca. The Triumphetta procumbens, a creeping plant, takes root like 
the Portulacca, in the most barren sands, and is very common. The 
Tournefortia and Scevola are also among the earliest species. The 
Pisonia, a tree of handsome foliage, the Pandanus or Screw-pine, and 
the Cocoanut, (always an introduced species,) constitute the larger 
part of the forests. In the Marshall Group, where the vegetation is 
more varied, Chamisso observed fifty-two native plants, and in a few 
instances the banana, taro, and breadfruit. 
The language of the natives indicates their poverty, as well as the 
limited productions and unvarying features of the land. All words 
like those for mountain, hill, river, and many of the implements of 
their ancestors, as well as the trees and other vegetation of the land 
from which they are derived, are lost to them; and as words are but 
signs for ideas, they have fallen off in general intelligence. It would 
be an interesting inquiry for the philosopher, to what extent a race of 
men placed in such circumstances are capable of mental improvement. 
Perhaps the query might be best answered by another, How many 
