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. Quite clearly, then, if,
instead of being 8:25 A.M., it were 8:25 P.M., then 8.5 times 14.67
seconds would have to be, not added, but SUBTRACTED; for, if, at
noon, the sun were 1 minute and 26 seconds behind time, and if it
were catching up with where it ought to be at the rate of 14.67
seconds per hour, then at 8.25 P.M. it would be much nearer where it
ought to be than it had been at noon.
So far, so good. But was that 8:25 of the chronometer A.M., or
P.M.? I looked at the Snark's clock. It marked 8:9, and it was
certainly A.M. for I had just finished breakfast. Therefore, if it
was eight in the morning on board the Snark, the eight o'clock of
the chronometer (which was the time of the day at Greenwich) must be
a different eight o'clock from the Snark's eight o'clock. But what
eight o'clock was it? It can't be the eight o'clock of this
morning, I reasoned; therefore, it must be either eight o'clock this
evening or eight o'clock last night.
It was at this juncture that I fell into the bottomless pit of
intellectual chaos. We are in east longitude, I reasoned, therefore
we are ahead of Greenwich. If we are behind Greenwich, then to-day
is yesterday; if we are ahead of Greenwich, then yesterday is to-
day, but if yesterday is to-day, what under the sun is to-day! - to-
morrow? Absurd! Yet it must be correct. When I took the sun this
morning at 8:25, the sun's custodians at Greenwich were just arising
from dinner last night.
"Then correct the Equation of Time for yesterday," says my logical
mind.
"But to-day is to-day," my literal mind insists. "I must correct
the sun for to-day and not for yesterday."
"Yet to-day is yesterday," urges my logical mind.
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