The legitimate
"chronometer-sight" method of ascertaining the longitude I had not
heard of - yes, I had heard of it. My first captain mentioned it
vaguely, but after one or two attempts at practice of it he
mentioned it no more.
I had time in the Fijis to compare my chronometer with two other
chronometers. Two weeks previous, at Pago Pago, in Samoa, I had
asked my captain to compare our chronometer with the chronometers on
the American cruiser, the Annapolis. This he told me he had done -
of course he had done nothing of the sort; and he told me that the
difference he had ascertained was only a small fraction of a second.
He told it to me with finely simulated joy and with words of praise
for my splendid time-keeper. I repeat it now, with words of praise
for his splendid and unblushing unveracity. For behold, fourteen
days later, in Suva, I compared the chronometer with the one on the
Atua, an Australian steamer, and found that mine was thirty-one
seconds fast. Now thirty-one seconds of time, converted into arc,
equals seven and one-quarter miles. That is to say, if I were
sailing west, in the night-time, and my position, according to my
dead reckoning from my afternoon chronometer sight, was shown to be
seven miles off the land, why, at that very moment I would be
crashing on the reef. Next I compared my chronometer with Captain
Wooley's. Captain Wooley, the harbourmaster, gives the time to
Suva, firing a gun signal at twelve, noon, three times a week.
According to his chronometer mine was fifty-nine seconds fast, which
is to say, that, sailing west, I should be crashing on the reef when
I thought I was fifteen miles off from it.
I compromised by subtracting thirty-one seconds from the total of my
chronometer's losing error, and sailed away for Tanna, in the New
Hebrides, resolved, when nosing around the land on dark nights, to
bear in mind the other seven miles I might be out according to
Captain Wooley's instrument. Tanna lay some six hundred miles west-
southwest from the Fijis, and it was my belief that while covering
that distance I could quite easily knock into my head sufficient
navigation to get me there. Well, I got there, but listen first to
my troubles. Navigation IS easy, I shall always contend that; but
when a man is taking three gasolene engines and a wife around the
world and is writing hard every day to keep the engines supplied
with gasolene and the wife with pearls and volcanoes, he hasn't much
time left in which to study navigation. Also, it is bound to be
easier to study said science ashore, where latitude and longitude
are unchanging, in a house whose position never alters, than it is
to study navigation on a boat that is rushing along day and night
toward land that one is trying to find and which he is liable to
find disastrously at a moment when he least expects it.
To begin with, there are the compasses and the setting of the
courses. We sailed from Suva on Saturday afternoon, June 6, 1908,
and it took us till after dark to run the narrow, reef-ridden
passage between the islands of Viti Levu and Mbengha. The open
ocean lay before me. There was nothing in the way with the
exception of Vatu Leile, a miserable little island that persisted in
poking up through the sea some twenty miles to the west-southwest -
just where I wanted to go. Of course, it seemed quite simple to
avoid it by steering a course that would pass it eight or ten miles
to the north. It was a black night, and we were running before the
wind. The man at the wheel must be told what direction to steer in
order to miss Vatu Leile. But what direction? I turned me to the
navigation books. "True Course" I lighted upon. The very thing!
What I wanted was the true course. I read eagerly on:
"The True Course is the angle made with the meridian by a straight
line on the chart drawn to connect the ship's position with the
place bound to."
Just what I wanted. The Snark's position was at the western
entrance of the passage between Viti Levu and Mbengha. The
immediate place she was bound to was a place on the chart ten miles
north of Vatu Leile. I pricked that place off on the chart with my
dividers, and with my parallel rulers found that west-by-south was
the true course. I had but to give it to the man at the wheel and
the Snark would win her way to the safety of the open sea.
But alas and alack and lucky for me, I read on. I discovered that
the compass, that trusty, everlasting friend of the mariner, was not
given to pointing north. It varied. Sometimes it pointed east of
north, sometimes west of north, and on occasion it even turned tail
on north and pointed south. The variation at the particular spot on
the globe occupied by the Snark was 9 degrees 40 minutes easterly.
Well, that had to be taken in to account before I gave the steering
course to the man at the wheel. I read:
"The Correct Magnetic Course is derived from the True Course by
applying to it the variation."
Therefore, I reasoned, if the compass points 9 degrees 40 minutes
eastward of north, and I wanted to sail due north, I should have to
steer 9 degrees 40 minutes westward of the north indicated by the
compass and which was not north at all. So I added 9 degrees 40
minutes to the left of my west-by-south course, thus getting my
correct Magnetic Course, and was ready once more to run to open sea.
