Tying things up with Iggy. (a forwarded post)

[scoutmom21113]

No: HPFGUIDX 95111

Potioncat asked: There a way of keeping tally using knots on strings.

Bookworm:
Thinking back to Mark Twain, he took his pen name from the use of 
soundings on the Mississippi River. IIRC, a line with a weight tied 
to the end would be thrown over the side of the ship and the depth 
would be called out in fathoms. One fathom is 6 feet, so "mark 
twain" would be 12 feet of water under the keel, and in the case of 
the river boats, meant a safe depth for the boat.  The fathom marks 
were usually made by tying knots in the line. This activity is 
called `sounding.' 

According to a navigation-related website from Queensland, Australia 
(http://education.qld.gov.au/curriculum/area/maths/compass/html/coast
alnav/cncha.html): "Knots were originally measured by a line on a 
reel with knots tied at intervals. The line had a gadget on the end 
that doesn't let water through. It was let out over the stern of the 
ship. When the first knot passed over the stern a 14-second 
hourglass timer was started. At the end of the 14 seconds the number 
of knots having passed over the stern was the speed of the ship in 
knots."  In modern times, the speed of a ship (nautical miles per 
hour) is still stated as `knots.' A ship traveling at 10 knots is 
moving 10 nautical miles per hour or about 11.5 statute miles per 
hour. 

For the true trivia buffs:
1 minute of latitude = 1 nautical mile = 1.852 kilometres = 1.1508 
statute miles, or 6,076 feet
Also, there are no ropes on a ship; there are lines. Lines used for 
different purposes have different names (i.e., stay, shroud, sheet). 

If there any deckhands on the list they could probably give 
additional uses of tally knots or better definitions. But back to 
Theo Nott. I don't remember hearing about any nautical experience in 
JKR's background, so her use of Nott/knot/not may be in a generic 
sense not a nautical sense, but we never know.

Ravenclaw Bookworm (who loves an excuse to use bits of odd trivia)