L I
.1 : I'
280 AprENnTx.
Some of the facts which seem to stand most in opposition to the
theory that deduces tides in the northern Atlantic from the movement
of a tide--wave originated in the great southern ocean are:
—the comparative naiTowuess of the space between Africa and America
; with the certainty that the sea is neither uniformly nor excessively
deep in that space,* and the triiiing rise of tide; not only
upon either nearest shore (where it does not exceed four or five feet
at the utmost), but at Ascension Island, where the highest rise is not
two feet.t Secondly, the absence of any regular tide about the wide
estuary of the river Plata, the situation and shape of which seems so
well disposed for recei\'ing an immense tide.+ Tliirdly, the floodtide
moving towards the west and south along the coast of Brazil,
rent from that which we have taken. The course of these lines in the
Pacific appears to be altogether problematical; and though those which
are drawn in the neighbourhood of the west coast of America connect
most of the best observations, they can hardly be considered as more than
conjecture : in the middle of the Pacific I have not even ventured to conjecture.
It only remains to add, that I shall be most glad to profit by
every opportunity of improving this map, and will endeavour to employ
for this purpose any information with which I may be supplied."—
pp. 234-5.
• Besides the ' Roccas' , Fernando de Noronha, and St. Paul rocks,
various accounts have been received, from time to time, of shoals near the
equator, between the meridians of fifteen and twenty.four degrees west.
There can be no doubt, from the descriptions, that many alarms have been
caused in that neighbourhood by earthquakes; which are, to my apprehension,
indications of no very great depth of water. In 1761, a small
. sandy island was said to have been seen by Captain Bouvet, of Le Vaillant.
This, if seen, has probably sunk down since. Krusenstern saw a
volcanic eruption thereabouts in 1806. In 1816, Captain Proudfoot, in
the ship Triton, from Calcutta to Gibraltar, passed over a bank, in latitude
0° 32' S. and longitude 17° 46' W. It appeared to extend in an east
and west direction three miles, and in a north and south direction one
mile. They sounded in twenty-three fathoms, brown sand ; but saw no
appearance of breakers.
+ At St. Helena it is not three feet: while at Tristan d'Acnnha there
is a rise of eight or nine feet under ordinary circumstances.
; I have passed months in that river without being able to detect any
periodical rise of water, which I could attribute to tide ; though it is said,
that when the weather is very settled, some indications of a tide may be
perceived.
APPENDIX. 281
from near Pernambuco to the ricinity of the river Plata; and lastly^
the ahnost uniformity of the time of high water along that extent of
the coast of Africa w-hich reaches from near the Cape of Good Hope
to the neighbourhood of the Congo.
Against the supposition that a tide-wave travels along the west
coast of America, from north to.south, are the facts—that the floodtide
impinges upon Chiloe and the adjacent outer coast, firom the
southward of west; that it is high water at Cape Pillar and at Chiloe,
including the intermediate coast, almost at one time; * that from
Valdivia to the Bay of Mexillones (differing eighteen degrees in latitude),
there is not an hour's difference in the time of high-water;
that from Arica to Payta the times vary gradually as the coast
trends westward; that from Panama to California, the times also
change gradually as the coast trends westward; and that from forty
to sixty north, high water takes place at one time.
Having thus stated a few of the difficulties to be encountered by a
theory which supposes such important tide-waves to move in the direction
of a meridian, rather than in that of a parallel, I wiU venture
to bring forward the results of much anxious meditation on the
• subject, trusting that they will be received by the reader—not as
assertions—not as conclusions to which assent is asked without a
reason for acquiescence being given—but as the very fallible opinion
of one indi^ddual, who is anxious to contribute a mite, however small,
towards the information of those for w^hom this work is more p^urticularly
written—namely, seafaring men; and who, if his ideas are
fallacious, will rejoice at their refutation by the voice of truth.
Resting in confidence upon the Newtonian theory—which assigns
as the primary causes of tides the attractions of the moon and sun—
I will make a few remarks, and then state some facts from which
to reason.
Some persons seem to view the tidal phenomena more in connection
with what would have happened had the globe been covered
with water, than with reference to what actually happens, now
that the oceans are nearly separated by tracts of land. They appear to
consider that the effects of the moon's attraction (leaiing the sun's out
of the question at present, as it is similar though smaller) are felt
only in vertical lines ; and they do not allow for the lateral action of
* Within about half an hour; an irregularity easily accounted for, and
to which any one place is subject.
b b