The Correct Magnetic Course was not the
Compass Course.
There was another sly little devil lying in wait to
trip me up and land me smashing on the reefs of Vatu Leile. This
little devil went by the name of Deviation. I read:
"The Compass Course is the course to steer, and is derived from the
Correct Magnetic Course by applying to it the Deviation."
Now Deviation is the variation in the needle caused by the
distribution of iron on board of ship. This purely local variation
I derived from the deviation card of my standard compass and then
applied to the Correct Magnetic Course. The result was the Compass
Course. And yet, not yet. My standard compass was amidships on the
companionway. My steering compass was aft, in the cockpit, near the
wheel. When the steering compass pointed west-by-south three-
quarters-south (the steering course), the standard compass pointed
west-one-half-north, which was certainly not the steering course. I
kept the Snark up till she was heading west-by-south-three-quarters-
south on the standard compass, which gave, on the steering compass,
south-west-by-west.
The foregoing operations constitute the simple little matter of
setting a course. And the worst of it is that one must perform
every step correctly or else he will hear "Breakers ahead!" some
pleasant night, a nice sea-bath, and be given the delightful
diversion of fighting his way to the shore through a horde of man-
eating sharks.
Just as the compass is tricky and strives to fool the mariner by
pointing in all directions except north, so does that guide post of
the sky, the sun, persist in not being where it ought to be at a
given time. This carelessness of the sun is the cause of more
trouble - at least it caused trouble for me. To find out where one
is on the earth's surface, he must know, at precisely the same time,
where the sun is in the heavens. That is to say, the sun, which is
the timekeeper for men, doesn't run on time. When I discovered
this, I fell into deep gloom and all the Cosmos was filled with
doubt. Immutable laws, such as gravitation and the conservation of
energy, became wobbly, and I was prepared to witness their violation
at any moment and to remain unastonished. For see, if the compass
lied and the sun did not keep its engagements, why should not
objects lose their mutual attraction and why should not a few bushel
baskets of force be annihilated? Even perpetual motion became
possible, and I was in a frame of mind prone to purchase Keeley-
Motor stock from the first enterprising agent that landed on the
Snark's deck. And when I discovered that the earth really rotated
on its axis 366 times a year, while there were only 365 sunrises and
sunsets, I was ready to doubt my own identity.
This is the way of the sun. It is so irregular that it is
impossible for man to devise a clock that will keep the sun's time.
The sun accelerates and retards as no clock could be made to
accelerate and retard. The sun is sometimes ahead of its schedule;
at other times it is lagging behind; and at still other times it is
breaking the speed limit in order to overtake itself, or, rather, to
catch up with where it ought to be in the sky. In this last case it
does not slow down quick enough, and, as a result, goes dashing
ahead of where it ought to be. In fact, only four days in a year do
the sun and the place where the sun ought to be happen to coincide.
The remaining 361 days the sun is pothering around all over the
shop. Man, being more perfect than the sun, makes a clock that
keeps regular time. Also, he calculates how far the sun is ahead of
its schedule or behind. The difference between the sun's position
and the position where the sun ought to be if it were a decent,
self-respecting sun, man calls the Equation of Time. Thus, the
navigator endeavouring to find his ship's position on the sea, looks
in his chronometer to see where precisely the sun ought to be
according to the Greenwich custodian of the sun. Then to that
location he applies the Equation of Time and finds out where the sun
ought to be and isn't. This latter location, along with several
other locations, enables him to find out what the man from Kansas
demanded to know some years ago.
The Snark sailed from Fiji on Saturday, June 6, and the next day,
Sunday, on the wide ocean, out of sight of land, I proceeded to
endeavour to find out my position by a chronometer sight for
longitude and by a meridian observation for latitude. The
chronometer sight was taken in the morning when the sun was some 21
degrees above the horizon. I looked in the Nautical Almanac and
found that on that very day, June 7, the sun was behind time 1
minute and 26 seconds, and that it was catching up at a rate of
14.67 seconds per hour. The chronometer said that at the precise
moment of taking the sun's altitude it was twenty-five minutes after
eight o'clock at Greenwich. From this date it would seem a
schoolboy's task to correct the Equation of Time. Unfortunately, I
was not a schoolboy. Obviously, at the middle of the day, at
Greenwich, the sun was 1 minute and 26 seconds behind time. Equally
obviously, if it were eleven o'clock in the morning, the sun would
be 1 minute and 26 seconds behind time plus 14.67 seconds. If it
were ten o'clock in the morning, twice 14.67 seconds would have to
be added. And if it were 8: 25 in the morning, then 3.5 times
14.67 seconds would have to be added.
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