1800's naval questions

[philip_thomson]

watching my favourite tv show today (hornblower) they had a guy (styles) on the lead line yelling out what depth of water they are in.

"by the mark 5"

"a quarter less 4"

"Deep 6"

does anyone know what these mean? are they in fathoms? foot? meters?

cheers phil

[Barrymundi]

Used to find depth and sea-bed characteristics, the lead and line was an ancient, but highly useful navigational aid. It consisted of a sounding lead attached to a line with evenly spaced knots or bits of colored cloth worked into it. The lead was tossed overboard and allowed to sink to the sea floor. Each mark was distinctive, and the distance between successive marks was constant; so water depth could easily be measured ("by the mark") or estimated ("by the deep"). When hauled aboard, the lead, by virtue of tallow packed into a small depression in its bottom, brought up a sample of the sea bed, useful in finding a safe anchorage.


Marks - The pieces of leather, on a lead-line (see "Lead.") In sounding it is usual to say, "By the mark" if the depth of water accords to a mark; if there be no "mark," as between three and five fathoms, the leadsman says, "By the deep four." The marks on the side of a ship which determine how much load or tonnage she can carry under different conditions. Also the designed waterline

The 'lead' was, as its name implies, a piece of lead which was used to find the depth of water. It was attached to a long rope which was marked off in fathoms (multiples of 6 feet, or 1.8m). After the lead was 'heaved' and the lead hit the seabed, the leadsman would count off the fathoms of rope and call out the depth of water. The American novelist Mark Twain got his pen-name from the cry of American leadsmen on river boats who would call out 'By the mark twain!', or two fathoms deep. The piece of lead was hollowed at the bottom and contained a lump of tallow (animal fat). This picked up material from the sea bed:- shingle, mud or sand. If it came up clean, the leadsman knew the sea bed was rock.

[Big_Kev]

I have been told that a fathom is the distance between the span of a mans arms as he hauls in the rope as described by Al. This is around six feet, but the bigger the man the deeper the fathom. A lot like a cubit realy.

I never knew that it was tallow that was used to pick up the bottom.
If you watch Master and Comander (Russ Crowe) this is featured in the film.

Knots were measured with a quarter circle flat board of 1 cubit radius dropped over the side of a sail ship and was rigged to drag through the water so it would pull the rope through the leadsmans hands. Knots were tied in the rope 12 fathom apart and the speed of the boat would pull as many knots through his hands in a time by a sand hour glass of 1 minute.
IE; If 6 knots went through his hands in 1 minute the boat was doing 6 knots.

[blaze]

I am for ever learning on this site, there is a real wealth of info out there
cheers
blaze

[Duyz72]

Hornblower, metres? Unless metric came in a bit early . . . . don't think so. Feet, as I recall he was not a Yank, so I doubt it. And being a nautical oriented arena, fathoms would have to be it.

I remember watching that show first time 'round. I loved it too! I'd love to have an old timber Sailer like those. Remember Alby Mangels? His World Safari Adventures? His boat was awesome, until it burned down of course. He was my inspiration to get one, do it up and cruise the world with a new hot chick every few episodes LOL

[DaveSue_Fishos_Two]

Questions have been answered here that I have long and often asked. It is great to be a part of this site with so many people who know these answers. One further question though: If the speed was measured at 6 knots that would be six knots a minute. How and why was this converted to knots per hour. Or am I wrong??? When we talk of present day boat speed aren't we talking knts per hour???

Cheers and thanks
Dave

[Morlers]

Knots is nautical miles per hour.

The six knots that passed through the leadmans hands in a minute was used to estimate the speed of the ship at six knots or six nautical miles per hour (or 11.1kph or 6.9mph). One knot equals 1.15mph or 1.852kph.

:) :)

Morlers

[revs57]

Good work guys!!!!

[DaveSue_Fishos_Two]

Thanks Morlers

But I'm still a bit confused. If the leadsman had six knots pass through his hands in a minute, and if there is 12 fathoms between each knot, that would mean that the ship had sailed 72 ft in a minute. ( 6 x 12 ). That would equate to 4,320 ft per hour. ( 60 x 72 ). Does that equal 6.9 mph???

Cheers
Dave

[theoldlegend]

A knot (or nautical or sea mile) has been measured at 6076.10333 feet. In my days at school, before electricity had been invented, 6080 feet was the rule. This equated to 1.1515 statute miles or 1.852 kilometres.

For practical purposes in navigation it is considered to represent one minute of arc of a meridian on the earth. There are 60 minutes in one degree, 360 degrees (meridians) in a circle. This would give a circumference of Earth at the equator of 21600 knots or 24872 statute miles or 40003 kilometres. The equatorial diameter of Earth has been estimated at 12756 kilometres, which gives a circumference of 40071 kilometres, or 21637 nautical miles (knots). It's pretty close which ever way you calculate it.

A hand lead was used for determining depths up to 25 fathoms and usually weighed 3 to 6 kilos. It was marked at intervals with strips of leather and also coloured rag.

A chip log was a simple pie shaped weighted piece of wood that was set astern and a rope paid out. By measuring the length of rope paid out, (usually with knots in it at certain distances) over a given time, then it was a simple matter to calculate the speed of the ship.

Say for example, if 500 feet of rope was paid out in one minute, then it could be assumed that 30 000 feet would be paid out in 1 hour, or 5.68 statute MPH, or 4.93 knots PH. I don't know how accurate the measurements used to be way back when.

Remember those Roman galleys with the slaves down below rowing their guts out while they were getting flogged by the blokes above?

I wonder if they used to get them up on the plane? Just a thought.

TOL

[Big_Kev]

Thanks Morlers

But I'm still a bit confused. If the leadsman had six knots pass through his hands in a minute, and if there is 12 fathoms between each knot, that would mean that the ship had sailed 72 ft in a minute. ( 6 x 12 ). That would equate to 4,320 ft per hour. ( 60 x 72 ). Does that equal 6.9 mph???

Cheers
Dave

Dave I have been looking for the old video tape I have of a documentry showing how it is done and the other methods of navagating for this era.

It shows how amazingly acurate the methods they used were in this time and would only be a couple of mile out when around the other side of the world.
It centers on the use of a timepeice (clock) and the need for it to be super acurate and not loose time from the point of origin.
It shows the many different clocks they made- some huge and the most acurate ended up being a pocket sized watch.

It is a very interesting documentry and well worth watching.
If I can find it I will check the info, but that give's you the idea how it is done and where the term knots come's from. #Don't dwell to much on the factual data as it needs to be confirmed.

Paying out the line was the easy part, I can imagine it would be a bitch to haul it back in.
Cheers Kev. #:)

[DaveSue_Fishos_Two]

Thanks fellas! I am more enlightened and with it now. LMAO at TOL....getting them up on the plane!! ;D ;D ;D
It really is fascinating stuff and incredible how those masters of old knew so much from bugger all instruments. We really do have it so easy these days. :)

Thanks again and cheers to you all
Dave

[Morlers]

Thanks TOL for your explanation. It saved my bacon. I had learnt all that stuff years ago but its amazing what you forget. If you don't use it you loose it as the saying goes.

:) :)

Morlers

[theoldlegend]

Hi Kev,

Your comments about the need for accurate timepieces in the old days jogged my memory. I think a world wide competition was set up for this. In the days of sextants and sightings and celestial navigation, an accurate timepiece was essential. Anyway, I'll try and look it up again. I see that you are at Manly. I'm at Birkdale. Maybe you could come round to my shed or I could go round to your shed and we could have a deep and meaningful discussion on the subject, assisted by some fluid.

Dave and Graeme,

It's been a long, long time since I last used a compass, but I can recall that if we found a secret spot x, then we would try and take 3 bearings on landmarks if we could make them out, take back bearings and spot x was somewhere inside the cocked hat thus marked on the chart.

I think that now if you find a good spot, you log it into your GPS and Bob's your uncle.

Regards,

John
TOL

[Morlers]

Hi TOL

Recently learnt about the 'cocked hat' when I did chart work for my VMR boat crew training. It was really interesting.

Also, I was visiting the Maritime Museum at Darling Harbour in Sydney last Christmas and one of their displays was on the competition you speak of to work out time using the lines of longitude. I can't remember how they did it though.

It worked out that 15 degrees longitude = 1 hour in time thus the Eastern seaboard of Australia is approximately 150 degrees Easy of Greenwich therefore = 10 hours before Greenwich Mean Time (GMT or ZULU).

At that stage, they had already figured out distance using lines of latitude (ie 1minute = 1 nautical mile).

See, you can teach old dogs new tricks.

:) :)

Morlers

[88fishframe]

I have been enjoying the info I am getting from this chat site, but DAMN !!!, do you guys ever get time to actually go fishing between getting involved in threads like this? But seriously, interesting stuff and go Hornblower and go Ably Mangels you legends. And go the Cowboys, still. :D

[theoldlegend]

I knew I'd find all this stuff. Got encyclopedias all over the table.

Because a lot of fleets were getting lost at sea by sailing east to west and vice versa, the English Parliament offered offered a prize of twenty thousand pounds in 1714 to anyone who could invent a time piece that was accurate to within the parameters that Parliament had set. Everybody was having a big problem "finding the longitude".

The issue was that the most accurate clocks of the time were pendulum clocks, but these could not be used on ships because of the rockin' and rollin'.

In 1761, a bloke called John Harrison invented a large timepiece (watch) that was installed on a ship and after 81 days sailing to the West Indies, the watch was found to be 5.1 seconds slow, giving a navigational margin of 1.25 miles, inside the margin of 30 miles set by Parliament. Later watches were set in gimbals on board ship.

Determining latitude depended on accurate timepieces and a knowledge of spherical trigonometry plus being able to see the sun, so I suppose they got better as time went on.

Once the prime meridian had been established as passing through Greenwich, a suburb of London, the French got pretty cranky because they calculated it should be established at a point east of Greenwich, which of course would put it in France. As instruments improved over time, I think the prime meridian was moved a few feet from its original calculation.

As Morlers says, each 15 degrees longitude means a time difference of 1 hour E or W of Greenwich Mean Time. 360 degrees/24 hours = 15 deg.

I can't find much about ships' logs at the moment, except that sand glasses were used a long time ago to time the distance of line paid out to estimate speed. Being sailing ships, I guess it was a constant job with wind shifts all the time etc.

Told wife I've got to get a hand held GPS. "Why" she said. Me: "I might get lost, but I'll always know where I am". I also suggested I could take the positions of the Wello Point hotel, the Cleveland Sands and the Grandview pub and enter them in as waypoints. "Come and get me! I'm at waypoint 2". She didn't reply.

TOL

[DaveSue_Fishos_Two]

I would love to sit at any of those waypoints with you TOL, and talk about this, and drink beer until cobwebs filled my hair. ;) Absolutely fascinating!!

Cheers
Dave

[theoldlegend]

Hi Dave,

Sorry that I rave on a bit. Navigation is a subject that I've been interested in for a long time, so I read up on it a fair bit.

I've previously borrowed books from the Cleveland library on coastal navigation and just swallow the stuff that's inside. Don't ask me why; I just like it. It gives me an insight as to how clever those mariners of old were when it came to finding their way around the world.

Regards,

John Miller

[DaveSue_Fishos_Two]

Clever and very bloody patient.

Dave

[Big_Kev]

In the end John it was concluded that a small Clock the size of a pocket watch was the most acurate and unafeccted by the rocking of the boat.
That was of course until the invention of the quartz powered digital.
Took a hell of a long time to get the next step.