Back in the days of the dominance of the British Navy (especially the 1600's through 1820 or so when the US Navy rose to power), the Brits were the force to be reckoned with on the seas. Not only did they conquer the art and science of sailing, but they also invented new techniques for navigation; it's not clear whether this particular subject was a British invention, or some other country .. the Portuguese, the Spaniards, the French and the Dutch were also a formidable forces at sea. The technique of "Dead Reckoning" was once such technique. The normal method of navigation was to use a sextant or other navigational device to calculate latitude and plot the course on navigational charts. The longitude was a bit more difficult and often relied on a significant investment in the Captain's "chronometer" (watch); conditions were horrendous, and seawater was known to ruin such devices regularly. Calculating by the moons on Jupiter was a bit more common, but this technique only worked when the skies were clear enough to see Jupiter at night. What then did they do during a protracted period of stormy weather? How to avoid being taken "by the lee", in other words, being blown onto a lee shore with no recourse to sail off the shore? First, we need to assure that we know where we are in the sea, and that any known shoals or islands are on our charts (which were an evolving piece of technology and not always accurate or complete!)
During these long periods, the answer is that the captain
would plot the progress of his ship on the ship's charts. In order to do so, he just needed to know the
speed and direction that the ship had been moving. Direction was easy: use the ship's compass,
but speed? There was no such thing as a
"speedometer" on a ship! Even
if there was, it was not a digital recording device that could play back all
known readings over a periodic measurement cycle. Instead, the ship relied on a rather odd
method of measuring speed: "heaving the log". What, you say? Yes, a log is literally a piece of wood or
log, to which a line was tied. The line
ran onto a spool and the line was tied up with knots, periodically spaced at a
known, accepted spacing. To measure
speed, which you guessed it, was in a measurement called Knots, the process was
not simple. Three ship's crew were
required: one to hold a sand glass which contained enough grains to run the
sand out for exactly 28 seconds, one to hold the spool of line that was attached
to the log as well as counting the speed, and one person to throw the log into
the sea (i.e. "heave the log"). The person with the log would heave the log
into the running sea and cry out "Nip" when the log hit the sea. On the cry of Nip, the sand glass was turned,
and the spooling operator would count the knots on the line as they passed
through his fingers while leaving the spool.
When the glass had run out, the glass bearer would cry out
"tuck" and the spool operator would declare the number of knots that
had passed through his fingers during the 28-second period. That, folks, is where we got the meaning of "Knots"
as a measurement of nautical speed!
So, what about logfiles??
Well, that precious value of Knots was brought to a special book, the Logbook,
where it was carefully recorded, along with the time that the measurement was
taken and the direction that the ship's compass currently read. These readings would then constitute speed
and direction that would be plotted on the ship's charts as part of the
exercise of "dead reckoning"! Logbooks
became synonymous with our more common term Logfiles as the books became simply
a set of papers in a file drawer. So you
see, logfiles are a descendent of the historical approach from naval days, on
down to our modern, computer world; they are often shortened to the more common
term "Logs", but you will find few folks that ever think about where
we got that term or why we are so comfortable with such jargon! My personal reflection as I think about this
whole process is that I'm often amazed that any explorer ever went sea, and
even more so that they ever returned from their voyages!
