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Old 21-01-2019, 19:25   #1
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Mistake in Bowditch!

While recently perusing an elderly copy of HO9, Bowditch, which e all know is the absolute "bible" of navigation, either I found a mistake, or I have been under a misaprehension for my entire navigating life. HO No9 1926, page 216 "The average speed of towing is about 1 1/2 knots per hour,". Can anyone with a later Bowditch see if this is corrected? Its toward the end of the chapter on marine surveying. My understanding is that knots per hour is a measure of acceleration.
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Old 21-01-2019, 19:45   #2
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Re: Mistake in Bowditch!

How old is the edition? EDIT... just noted ..1926

There was a time when 'knots per hour' was in fairly common usage...

… the ship went ten knots an hour with a prodigious sea....
— Admiral George Anson, Anson's Voyage Round the World, 1748

… we were at that time running at the rate of six knots an hour….
Captain James Cook, Voyages, 1790

Usage continued by others with some experience of the nautical life:

When the ship was running nine knots an hour, these animals [porpoises] could cross and recross the bows with the greatest of ease, and then dash away right ahead.
— Charles Darwin, The Voyage of the Beagle, 1839

We were gliding along, hardly three knots an hour….
— Herman Melville, Mardi: And a Voyage Thither, 1849

Tracked them down in the one spot here...

https://www.merriam-webster.com/word...-an-hour-wrong
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Old 21-01-2019, 19:48   #3
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Re: Mistake in Bowditch!

Dr. Robin G. Stuart has identified at least eight errors and issues in the 2002 edition of Bowditch (some of which have since been corrected). It should come as no surprise that this or any work may contain some errors.


BTW, many different editions of Bowditch can be examined via links provided here.
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Old 21-01-2019, 19:53   #4
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Re: Mistake in Bowditch!

When towing you'll obviously wear out the towrope. So you need to keep tying new knots. 1 1/2 times per hour.
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Old 21-01-2019, 20:20   #5
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Re: Mistake in Bowditch!

A look into the history of knots v "knots an hour"


'Knots an hour'


inter alia:

"We can suggest a tentative date for the “reformation” in American usage, since it is said that the 1881edition of Bowditch’s American Practical Navigator, a standard textbook mentioned by Kipling in Captains Courageous (page 124), amended “knots an hour” to “knots” throughout its pages."
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Old 22-01-2019, 08:55   #6
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Re: Mistake in Bowditch!

According to the link in Stu's post, the knots on a log line are eight fathoms apart. The log glass counted 28 seconds. So if, say, five knots had been counted, the ship was going five knots per 28 seconds. Not five knots per hour.

Which is why I always thought "knots per hour" was wrong. I'm willing to stand corrected if anyone has a better explanation.
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Old 22-01-2019, 09:39   #7
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Re: Mistake in Bowditch!

I just looked in the latest on-line version and it's all converted to "knots".
https://en.wikisource.org/wiki/The_A...ical_Navigator

By the way, it's ironic finding errors in "Bowditch" as the origin of the book back in the 18th Century was to correct other's errors. The preface included this story:
John Hamilton Moore’s The Practical Navigator was the leading navigational text when Bowditch first went to sea, and had been for many years. Early in his first voyage, however, the captain’s writer-second mate began turning up errors in Moore’s book, and before long he found it necessary to recompute some of the tables he most often used in working his sights. Bowditch recorded the errors he found, and by the end of his second voyage, made in the higher capacity of supercargo, the news of his findings in The New Practical Navigator had reached Edmund Blunt, a printer at Newburyport, Mass. At Blunt’s request, Bowditch agreed to participate with other learned men in the preparation of an American edition of the thirteenth (1798) edition of Moore’s work. The first American edition was published at Newburyport by Blunt in 1799. This edition corrected many of the errors that Moore had included.
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Old 22-01-2019, 10:06   #8
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Re: Mistake in Bowditch!

Quote:
Originally Posted by CaptTom View Post
According to the link in Stu's post, the knots on a log line are eight fathoms apart. The log glass counted 28 seconds. So if, say, five knots had been counted, the ship was going five knots per 28 seconds. Not five knots per hour.

Which is why I always thought "knots per hour" was wrong. I'm willing to stand corrected if anyone has a better explanation.

I agree entirely. Maybe some time, somewhere, it was common to say "knots per hour", but it's still bastardized usage.
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Old 22-01-2019, 15:37   #9
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Re: Mistake in Bowditch!

Guys, the meaning of "Get thee to a nunnery!" has changed since Shakespeare wrote that line, too. Doesn't mean it was a mistake or that it was wrong, just means when you're reading something a hundred (or 500) years old, you've got to read it in context.

Charts that say "HERE BE DRAGONS!" might very well have been correct 400 years ago. Dragons tend to move around over the years.
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Old 22-01-2019, 16:17   #10
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Re: Mistake in Bowditch!

'Knots per hour' is not bastardized usage.... it is archaic usage.

When in quite common use it simply relied on 'knot' = 'mile' rather the modern usage where 'knot' = 'mile per hour'.
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Old 22-01-2019, 19:21   #11
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Re: Mistake in Bowditch!

Quote:
Originally Posted by El Pinguino View Post
'Knots per hour' is not bastardized usage.... it is archaic usage.

When in quite common use it simply relied on 'knot' = 'mile' rather the modern usage where 'knot' = 'mile per hour'.
OK, language is a living thing, and usage changes. I get that.

But I still can't see why you'd count out five knots in 28 seconds, and call it 5 knots per hour. When did an hour mean 28 seconds?

Likewise, a knot has always been something you tie in a rope or line. It was never a mile, and it never had anything to do with miles until people started tossing them over the side, counting out 28 seconds, and converting knots per 28 seconds into miles per hour.

Sure, there are probably things I say which can be considered oxymorons. I'm not saying you can't do that, if it's a common usage. I'm just saying it's technically incorrect.
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Old 22-01-2019, 19:58   #12
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Re: Mistake in Bowditch!

You can overthink this stuff....

Maybe you should have a chat with Edmund Gunter or Willebrord Snellius and try and sort it out with them ... but they are both dead....
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Old 23-01-2019, 06:07   #13
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Re: Mistake in Bowditch!

Quote:
Originally Posted by El Pinguino View Post
'Knots per hour' is not bastardized usage.... it is archaic usage.

When in quite common use it simply relied on 'knot' = 'mile' rather the modern usage where 'knot' = 'mile per hour'.



Something can be BOTH bastardized AND archaic


I agree with Cap'n Tom.


When was a "knot" ever a "mile"? It's a literal knot in the log line.



Same in other languages -- uzel, Knoten, noud.
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Old 23-01-2019, 07:23   #14
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Re: Mistake in Bowditch!

Quote:
Originally Posted by Dockhead View Post
...


When was a "knot" ever a "mile"? It's a literal knot in the log line.


Knots were tied in the line of a "Chip Log" at one fathom intervals, roughly 1/1000th of a "mile", and counted for 10 minutes as they ran out after the "chip" was heaved overboard. Our first "knot meter" was a chip log, the chip being a triangular piece of wood weighted on one corner so that it floated vertically and would remain static in the water well enough to pull the log line over the transom. One multiplied the result by 6 to determine the number of of knots per hour. Hence the term. Stepping up (then) to a Walker Patent Log, with a trailing spinner, was a real "high tech" improvement (unless a Dolphin or Shark grabbed the spinner of course!).
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Old 23-01-2019, 07:46   #15
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Re: Mistake in Bowditch!

Quote:
Originally Posted by svHyLyte View Post
Knots were tied in the line of a "Chip Log" at one fathom intervals, roughly 1/1000th of a "mile", and counted for 10 minutes as they ran out after the "chip" was heaved overboard. Our first "knot meter" was a chip log, the chip being a triangular piece of wood weighted on one corner so that it floated vertically and would remain static in the water well enough to pull the log line over the transom. One multiplied the result by 6 to determine the number of of knots per hour. Hence the term. Stepping up (then) to a Walker Patent Log, with a trailing spinner, was a real "high tech" improvement (unless a Dolphin or Shark grabbed the spinner of course!).

So let's assume a speed of 6 nautical miles per hour.


That's a full mile of line dragged out in 10 minutes which is 1000 knots. Multiply that you 6 and you have 6000 per hour. Something doesn't sound right there..



If you are doing 12 Nm/hr you need 2 miles of line.
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