CHANGES OF LEVEL 413 
finer material at Ewa, and occurring at a height of sixty feet above 
the sea. We were informed of similar deposits up a valley on this 
part of the island, at a much greater elevation, but did not have an 
opportunity to examine them. In crossing the mountains of the 
western peninsula of Maui, Dr. Pickering observed a basaltic pudding- 
stone, or conglomerate of half-rounded stones, two thousand feet 
above the level of the sea. On Mount Kea, similar beds were met 
with by Dr. Pickering at a height of six thousand feet. On the 
island of Tahiti a coarse conglomerate of partially rolled fragments 
was observed by the writer up a branch from the Matavai Valley, at 
an elevation of about one thousand five hundred feet above the sea. 
From these facts, and others similar in the Feejees and Samoa, we 
may infer that many of the islands were at a lower level during some 
portion of their early history, while their formation was in progress. 
But they do not prove their submarine origin, nor anything definite 
respecting the actual condition of the seas. ‘This remains for future 
exploration. ‘The compact rocks of the interior of the islands, and 
especially the crystalline syenitic rocks of Tahiti, were at one time 
considered by the author evidence of their eruption beneath the pres- 
sure of an ocean; but this is not satisfactory, (see p. 377,) since the 
pressure required for compactness would be afforded in the interior of 
a volcano, by the molten lava itself. 
From the surface of Mount Loa we learn that the occurrence of 
beds of lava with ropy lines characterizing the surface (produced by 
the flowing of the lava) indicates a subaerial origin. In ejections 
beneath the sea, the surface of the lava is so acted upon by the cold 
waters that such lines are not preserved. From these indications 
we ascertain that Tahiti, Upolu, Savaii, Oahu, Maui, and Kauai were 
nearly at their present height when the dafest eruptions took place. 
We learn again from Mount Loa, that a subaerial origin is shown 
by a great number of lateral cones of lava or cinders. ‘The absence 
of these small cones from Tahiti cannot, however, prove the contrary ; 
since the island has been subject to extensive denudation, and these 
minor craters would be the first parts to disappear. Western Maui, 
as well as the larger part of Kauai, resembles ‘Tahiti. On Hastern 
Maui and Savaii these lateral cones are still numerous, and the sur- 
face of these lands bears every evidence of recent, subaerial fires, and 
little denudation. 
The cavernous nature of Mount Loa, is another point that may be 
looked upon as proof of subaerial origin; and it is conclusive upon 
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