The Express.
London, England, 1868-10-23 00:00:00

TUE tiIaItiIDENCH OF HAWAII,

The intelligence which we published yesterday
respecting the progress of the subsidence of
Hawaii, is worthy of careful consideration. It
appears that since the groat submarine eruption
which took place some months ago, the island has
Lein gradually sinking, the depression of the
southern and western shores having amounted to
several feet ; while that of the northern and
eastern shores has not exceeded a few inches. ft
is important to attend to this peculiarity. IL•►d
the change of the sea-level been uniform in all
parts of the island, we might have boon doubtful
as to the seat and nature of the disturbance. The
gradual elevation of a widely-extended pinion of
the bed of the Pacific Ocean would, in that ease,
have accounted as satisfactorily for tho diminu-
tion in the height of Hawaii above the sea
level as the sinking of the island itself. But the
inequality. in the motion of subsidence points at
once to therm] character of the disturbance, which
doubtlees only effort' Hawaii and its immediate
neighbourhood. We do not think, however, that
the sinking of the island has been a gradual pro-
cess. Far more probably it took place simulta-
neously with the outburst of submarine fire which
caused so much mischief last April. The manner
in which the Honolulu correspondent of the New
York Tribune refers to the discovery of the change
does not certainly convey the notion that any slow
process of change has been detected. "It is
believed," ho writes, " that Hawaii is slowly
sinking into the ocean. Ever since June last
unusually high tides have prevailed along the
southern and eastern shores, and it is now evident
that the ishmd has sunk," &c. It appears to us
that the inhabitants do not fear that any further
sinking will take place, unless—which seems
unlikely—there should presently be other sub-
marine explosions.
Very interesting also is the account of the waves
which spread across to Hawaii from Peru, after '
the great earthquake of August 13-16 last. "The
first of these waves was observed at Honolulu on
the night of the 13th of August, and at almost
the same moment it was noticed 200 miles to the
south-east. They were more powerful at those
parts of Hawaii which are nearest to the South
American coast. They rolled in at the rate of
three or four per hour for four days. They were
not like the sweep of the furious breakers that
lashed the shores during the April eruptions, but
appeared to be the effect,, of some gigantic oscil-
lation across the Pacific." There can be no doubt
whatever that these waves were duo to the great
earthquake which recently desolated the coast of
Peru and Ecuador. The waves must have been
transmitted across the whole distance which sepa-
rates nawisii from Peru in the course of a few
Lours, or probably at the rate of about I,ooa miles
per hour. This does not exactly agree with the
statement that the wave was noticed almost at the
same moment at two places 200 miles apart (and
lying nearly in the direction of the Vilivol pro-
gress); but probably there is some mistake in this
account. The difference of time must have been
nearly a quarter of an hour.
It would be important if wo could determine
the exact rate at which sea-waves traverse the
Pacific Ocean, since it has been shown that a rela-
tion exists between the depth of an ocean and the
rate at which waves of given dimensions traverse
it. We say of given dimensions, but it is net
necessary that all the dimensions of a wave should
be known in order that its ascertained velocity
should suffice for the determination of the depth
of the oc•aan across which it has been propagated.
All that is necessary is that the breadth of the
wave should be known—that element being mea-
sured from summate summit of successive rollers.
They following Table is derived from one calculated
by Mr. Airy, the Astronomer Royal. It presents
the relation between the breadth of sea-waves,
their velocity, and the depth of the sea they are
traversing: