ORIGIN OF ISLANDS. 11 
Tahiti, the principal of the Georgian Islands, is 
the most extensive and lofty of the group. It is 
formed by two peninsulas, united by a long broad 
isthmus. The largest is circular in form, and above 
twenty miles in diameter. ‘The smaller is oval, and 
is sixteen miles long, and eight broad. The circum- 
ference of the whole island is 108 miles. The whole 
of the islands are mountainous in the interior, and 
have a border, from one to four miles wide, of 
rich level land, extending from the base of the high. 
land to the sea, and though the outline of each 
has some peculiarity distinguishing it from the 
rest, in their general appearance they resemble 
each other. Tetuaroa, Tubai, Lord Howe’s, and 
Scilly islands, however, form exceptions, as they 
are low coral islands, seldom rising many feet 
above the sea. Eimeo is supposed to be about 
twenty-five miles in circumference, Huahine pro- 
bably more than thirty, and Raiatea somewhat 
larger. The others, though equally elevated, are of 
smaller extent. 
A corresponding resemblance to each other pre- 
vails in the geological structure of the principal 
clusters and surrounding islands; the substances 
of which the majority are composed being the same, 
while each island has some distinguishing pecu- 
liarity. 
There is no reason to suppose that either Tahiti, 
or any adjacent island, is altogether volcanic in 
its origin, as Hawaii, and the whole of the Sand- 
wich Islands, are. The entire mass, compos- 
ing the latter, has evidently been in a state of 
fusion, and in that condition has been ejected from 
the focus of an immense volcano, or volcanoes, ori- 
ginating, probably, at the bottom of the sea, and 
forming, by their action through successive ages, 
