, I I'K-i
S I i ' L
290 APPENDTX,
from each side, that the western portion of this zone is affected.
Otaheite is thus at the edge, or Umit, of four tides—one east, another
west, a third to the north, and a fourth to the south, and as
these tides are moving with different impulses, and at different
times, it is not at aU surprising that they should almost neutralize
each other at Otaheite. As we go west or east of that island, we
find the tides augmenting gradually in height. At the Friendly
Islands they rise five feet, and at the Gambier Islands three feet.
Respecting the twelve hour tide at New Ireland, and at other
places in the Indian archipelago-appeal to facts, so far as we can
trace the tides at present, tends to confirm the explanation of Sir
Isaac Newton, which consisted in supposing that such tides are compounded
of t^'o tides, which arrive by different paths, one six hours
later than the other. " When the moon is in the equator, the
morning and evening tides of each component tide are equal, and
the tides obUterate each other by interference, which takes place
about the equinoxes. At other periods the higher tides of each component
daily pair, are compounded into a tide which talies place at
the intermediate time, that is, once a day ; and this time wiU be
after noon or before, according to the time of year."—WheweU, in
PhU. Trans. 1833, p. 224.
At New Ireland, the time of high water is about 3 ; but at New
Caledonia it is 9. Again, at the north-west coast of Australia it is
12 • and at the eastern approach to Torres Strait, 10 : at the Phihppine
Islands it is 4 ; and at Loo Choo, 10. Now here are various
times of tide, and different impulses, crowded together into a comparatively
small space, sufficient to perplex any theorist di the present
day. Omng to local configurations, and a variety of incidental
circumstances, we find every kind of tide in this region, in
a space sixty degrees square. Although tidal impulses, waves
and resulting currents are checked and altered by the broken land
of the Indian archipelago, they cannot be suddenly destroyed, or
prevented fi'om infiuencing each other, whfle communications, more
or less open, exist in so many directions.
At the Sandmch Islands there is said to be very little tide. As it
is high water in 40° N., on the American coast, at 8 ; at which time
it is also high water at the Galapagos, it appears that the two
zones of the ocean—one about the equator, and the other near 40 N.
—have high water, in the meridian of the Sandwich Islands, at two
APPENDIX. 291
very different times ; and that the high water of the northern zone
will have passed that meridian about three hours before the equatotorial
wave. Impulses derived from them might succeed one
another at an intermediate point, such as the Sandwich Islands.
Besides which, there is the tide of their own zone to be considered;
in consequence of which alone it might be high water at about 6 :
thus these islands are so situated as to receive at least three tidesone
primary and two derivative—whose respective times of high water
are 1, 6, and 10, a succession which may well be supposed to neutralise
any ebb, and maintain the water thereabout above its natural
level, independent of tide.
About the Strait of Magalhaens, and along the eastern coast of
Patagonia, there are very high tides; apparently complicated, but
perhaps less so than is usually believed.
A powerful tide arrives at the Falklands, and at the east end of
Staten Land, at about 9 ; which is opposed by another powerful
tide arriving from the west. The union of these two accumulates
the water between Tierra del Fuego and the Falldands, and on the
east coast of Patagonia.
Within the Strait of Magalhaens, westward of the Second Narrow,
it is high Water at about 4.40, and the tide rises six feet:
but eastward of the First Narrow it is high at 1.30, and the tide rises
forty feet.
Now, as in one case the sea only rises three feet, and in the other
twenty, above its mean level, every one would expect to find a rush
of water through the Narrows, from the high sea to the low, and
such is the fact. From ten to four the water runs westward with
great velocity, and from four till ten it rushes eastward. During the
first mterval, from ten to four, the eastern body of water, between
Tierra del Fuego and the Falklands, is above the mean level; and
during the latter interval, from four till ten, it is below the mean
level—that which it would have if there were no tides.
From 50° S. to near Blanco Bay in 40° S. the tide-wave certainly
travels along the coast to the north; but this is a derivative from the
meetmg of tides above-mentioned, combined with the primary tides
on the coast traversed. In this way principally may we account
for a high tide m one place on this coast, and a low one on another
(simflarly situated, though differing in latitude) ; and, again, a high
tide at another place. Durmg the twenty-four hours that the deri