414 PACIFIC OCR AWN: 
this point, as far as regards the exterior coating of Mount Loa, the 
only part exposed to view. Like the two preceding kinds of evidence, 
it is of very difficult application. In Eastern Oahu, however, in the 
lower slopes beyond Diamond Hill, there are many caverns so similar 
to those of Mount Loa, that they clearly evince that the land was 
above water when the ejections took place. 
The recently ejected rocks of Mount Loa, though often very com- 
pact, still contain some ragged cellules; and this kind of cellule is a 
good proof of the rocks cooling without pressure above. ‘The appli- 
cation of this test leads us to no different results from those already 
stated. 
We arrive, therefore, at the conclusion, that while it is apparent 
that the latest eruptions of many of the Pacific islands were subaerial, 
and the most of these lands were at a much lower level in the course 
of their progress, we cannot point out which were of submarine 
origin; and of course we learn nothing with regard to the earliest 
condition of these centres of eruption, from examining the rocks above 
the present sea level. 
The action of the sea on the cliffs of the islands before these shores 
were protected by reefs, is another source of evidence with regard to 
the level of the land at an early epoch. Such facts are identified 
with difficulty ; and we have distinguished only a single undoubted 
case. ‘This occurs on the north side of Vanua Lebu, one of the 
Feejees, where there is a cylindrical well-like cavity, which was 
probably a former blow-hole. It is already described on page 350. 
V. GENERAL ARRANGEMENT OF LAND IN THE PACIFIC. 
The linear ranges of islands in the Pacific, and the extent of the 
great chains over this third of the earth’s surface, have been pointed 
out in an early part of this volume.* This arrangement, in lines, 
has often been correctly attributed to the opening of fissures, and we 
have pursued this view to some interesting conclusions respecting the 
Hawaiian Islands. We repeat here our general deductions, adding 
farther illustrations, where the subject seems to require it. 
* The pages referred to should be reperused in connexion with this chapter, and as 
introductory to it. The facts might have been deferred to this place: yet were properly 
connected with a general review of the topography of the ocean. ‘The following discus- 
sions could not have been given in that place without anticipating many facts and conclu- 
sions since detailed. 
