Mike Hammond
Welcome back By the late 1400 I decided to head back to Europe and sail the Atlantic Ocean. Sailors that I had met talked of more adventurous captains that were willing to sail to the ends of the earth in search of riches, adventure or maybe just fame. I was not concerned with their motives I just wanted to travel to new places. So far to measure our speed and figure out where we were on our charts we had to make good guesses. In order to help us with these guesses we would through something that could float over the side and then time it as it floated away. Usually what we threw over the side was a large piece of would or a log so the technique began to be called heaving the log, since normally it involved heaving a log overboard. It was not very accurate but at the time it was the best that we had (Nautical). Over time sailors developed a unit of measurement quite unique from the meter or mile that you use on land. It was called the nautical mile and is about 6067 feet or about 1.15 miles. It was originally defined as the distance of one minute along a meridian on the surface of the earth. It is an average of numbers because of variations of the curvature of the earth but the important thing to remember about it is that it is the preferred way that sailor’s measure the distance that we travel. When we wanted to measure speed it was going to be measured in nautical miles per hour. How, might you ask did we get from nautical miles per hour to Knots, the way we measure speed on ships and even in your airplanes today. A knot is simply one nautical mile per hour, but how did the term come about. It doesn’t seem to have any connection to heaving the log so there must be some story. One problem with heaving the log was that eventually, being out to sea, we would inevitable run out of logs to through overboard (Mordica). This led to all sorts of fights among us as we argued over whose possessions would go over the side next. I would imagine if things got too ugly the result may have been one less sailor on board to argue about it after watching a man instead of a log drift away from the ship. Eventually someone came up with the idea to tie a rope to the log and then we could just bring the same log back every time and never run out of wood. Sometime in the 1500’s, though I’m not exactly sure when, the method used to estimate speed advanced significantly. A tool was devised that allowed us to get a very god estimate of our speed and was called either a chip log or Dutchman’s log depending on where you were from.  Photo of a Chip Log From the Musée de la Marine, Paris. © Rémi Kaupp, CC-BY-SA, Wikimedia Commons
Originally viewed at http://en.wikipedia.org/wiki/Chip_log Most of the men I sailed with called it a chip log and so will I. A chip log was a simple device that consisted of a piece of wood attached to a rope that was wound on a reel. The rope had a knot tied in it every 47.3 feet. To use the log the wood would be thrown overboard and sand filled timer, much like an hourglass, would be turned over. The timer counted down 28 seconds, we wanted to leave the log out for 30 so we took of two seconds to account for the time it took us to throw the log and flip the timer. The number of knots that passed through our hands was equal to the number of nautical miles per hour that we were traveling, and there is the way that the term knot came into our vocabulary. The reason that this works is simple math. Instead of leaving the rope out for an hour and counting how many miles of rope were let out we simply scaled it back to a practical amount of time and distance. There are 120 thirty second intervals in an hour and 120, 47.3 foot intervals would equal about 1 nautical mile. Although it doesn’t work out to be exact it is pretty close and certainly close enough for us sailor's. The chip log was first referred to by William Bourne in A Regiment for the Sea in 1574. This book was a reference book to all sailor’s and contained information valuable, including tide charts and information about longitude the phases of the moon and many other things important to navigation. The fact that a chip log is mentioned in his writings speaks to the popularity and usefulness of the device. The chip log enabled us to accurately measure our speed over
great distances even when out of sight of land and in the dark because we could
feel the knots. The device helped to
create a new term for nautical miles per hour, the knot, which is still used by you
today. The ability to track speed,
coupled with the ability to determine direction with the compass, allowed
sailors to accurately mark their positions on charts making longer voyages
possible and much safer. I think that Trans-Atlantic voyages were made possible, and definitely safer and easier, with the invention and widespread use of the chip log, coupled with compasses and increasingly accurate charts. It is quite possible that Columbus used a similar device on his Voyages to America and very likely that most of the original settlers of the new world owe their safe arrival to the chip log and brave sailors who used them on their journey across the Atlantic. Notes Bourne, William. Regiment for the Sea. 1. London: By [Henry Bynneman for] Thomas Hacket, and are to be solde at his shop in the Royall Exchaunge, at the signe of the Greene Dragon, 1574. from Early English Books Online via the University of Oklahoma LORA system Mordica, Allen. "The Speed Log --History, Construction and Use." The Navy and Marine Living History Association. NMLHA. 1 Dec 2008 <http://www.navyandmarine.org/planspatterns/speedlog.htm>. "Nautical Mile." Encyclopedia Britannica. 2008. Encyclopedia Britannica Online. 30 Nov. 2008 <http://www.britannica.com/EBchecked/topic/406739/nautical-mile>. Primary Source Note For a primary source I used William Bourne’s Regiment for the sea. This book was published by a gunner from a ship in 1574. After viewing it online at EEBO I was fascinated on the depth of things covered in the book and how they can still apply today. The fact that a Chip Log is mentioned in it helps show the importance of this young device to marine navigation. Secondary source note
My secondary source is the web document by Mordica. It is a signed work published on a reputable
historical website by a named author. The
author posses an obvious knowledge of the subject matter and illustrates this
by providing detailed instructions on the construction of a working chip
log. Image Information Nautical Mile Definition from Wikimedia Commons http://en.wikipedia.org/wiki/Nautical_mile Photo of a Chip Log From the Musée de la Marine, Paris. |
