(Vol. viii., p. 102.)
This question was asked by H., and at p. 479. an answer to it was
undertaken by ESTE. But, probably from over-anxiety to be very brief, ESTE
was betrayed into a most strange and unaccountable misstatement, which
ought to be set right before the conclusion of the volume; since, if
correctness be generally desirable in all communications to "N. & Q.," it
is absolutely indispensable in professed answers to required information.
ESTE says:
"A person sailing to our Antipodes westward will lose twelve hours; by
sailing thither eastward he will gain twelve hours."
This is quite correct. But if one person lose twelve, and another gain
twelve, the manifest difference between them is twenty-four; and yet ESTE
goes on to say:
"If both meet together at the same hour, say eleven o'clock, the one
will reckon 11 A.M., the other 11 P.M."
This is the misstatement. No two persons, by any correct system of
reckoning, could arrive at a result which would imply a physical
impossibility; and it is needless to say that the concurrence of A.M. and
P.M. at the same time and place would come under that designation. What
ESTE should have said is, that both persons meeting {649} together on the
same day, if it be reckoned Monday by the one, it will be reckoned Tuesday
by the other. They may differ as to Monday or Tuesday, but they cannot
rationally differ as to whether it is day or night.
It may be added that, no matter where these two persons might meet, whether
at the Antipodes or at any other place, still, upon comparing their
journals, there would always appear a day's difference between them; and if
they were to keep continually sailing on, one always towards the west, and
the other always towards the east, every time they might meet or cross each
other, they would increase the difference between them by an additional
day.
Whence it follows, that if two ships were to leave England on the same day,
one sailing east by the Cape of Good Hope, and the other west by Cape Horn,
returning home respectively by the opposite capes; and if both were to
arrive again in England at the same time, there would be found in the
reckoning of the eastern vessel two entire days more than in that of the
western vessel. Nor would this difference be merely theoretic or imaginary;
on the contrary, it would be a real and substantial gain on the part of the
eastern vessel: her crew would have consumed two whole rations of
breakfast, dinner, and supper, and swallowed two days' allowance of grog
more than the other crew; and they would have enjoyed two nights more
sleep.
But all this is not an answer to H's question; what he wants to know is
whether the day at the Antipodes is twelve hours in advance or in arrear of
our day and, whichever it is, why is it?
But here H. is not sufficiently explicit. His question relates to a
practical fact, and therefore he should have been more particular in
designating the exact habitable place to which it referred. Our Antipodes,
strictly speaking, or rather the antipodal point to Greenwich Observatory,
is 180deg of east (or west) longitude, and 51deg 28' &c. of south latitude.
But this is not the only point that differs by exactly twelve hours in time
from Greenwich; all places lying beneath the meridian of 180deg, "our
Periaeci" as well as "our Antipodes," are similarly affected, and to them
the same question would be applicable. H. is right, however, in assuming
that, with respect to that meridian, the decision must be purely arbitrary.
It is as though two men were to keep moving round a circle in the same
direction, with the same speed, and at diametrically opposite points; it
must be an arbitrary decision which would pronounce that either was in
advance, or in arrear, of the other.
Regarding, then, the meridian of 180deg as the neutral point, the most
rational system, so far as British settlements are concerned, is to reckon
longitude both ways, from 0deg to 180deg, east and west from Greenwich; and
to regard all west longitude as in arrear of British time, and all east
longitude as in advance of it. And this is the method practised by modern
navigators.
It is not, however, in obedience to any preconceived system, but by pure
accident, that our settlements in Australia and New Zealand happen to be in
accordance with this rule. The last-named country is very close upon the
verge of eastern longitude, but still it is within it, and its day is
rightly in advance of our day. But the first settlers to Botany Bay, in
1788, were actually under orders to go out by Cape Horn, and were only
forced by stress of weather to adopt the opposite course by the Cape of
Good Hope. Had they kept to their prescribed route, there cannot be a doubt
that the day of the week and month in Australia would now be a day later
than it is.
The best proof of the truth of this assertion is, that a few years
afterwards a missionary expedition was sent out to Otaheite, with respect
to which a precisely similar accident occurred; they could not weather Cape
Horn, and were forced to go round, some twice the distance out of their
way, by the Cape of Good Hope; consequently they carried with them what may
be called the eastern day, and since then that is the day observed at
Otaheite, although fully two hours within the western limit of longitude.
From this cause an actual practical anomaly has recently arisen. The French
authorities in Tahiti, in accordance with the before-mentioned rule, have
arranged their day by _western longitude_; consequently, in addition to
other points of dissent, they observe the Sabbath and other festivals one
day later than the resident English missionaries.
I have extended this explanation to a greater length than I intended, but
the subject is interesting, and not generally well understood; to do it
justice, therefore, is not compatible with brevity. Much of what I have
said is doubtless already known to your readers; nevertheless I hope it may
be useful in affording to H. the information he required, and to ESTE more
fixed notions on the subject than he seems to have entertained when he
wrote the answer referred to.