Summary - The End

CIRCLES OF UNCERTAINTY

(From the text of a lecture at the conference to celebrate the 25th. anniversary of the Raising of the Mary Rose, October 2007 )


I took part in the BBC tv series about Endeavour as one of the team of navigators, working and living under something close to eighteenth century conditions, and I then signed on as an ordinary crew member to help to sail Endeavour from Fremantle, in Australia, to Whitby, in Yorkshire, around Cape Horn from West to East pondering every day on the extraordinary skills of the old navigators and the extraordinary difficulty of what they did. I spent 166 days at sea on Endeavour in twelve months, so there was time for reflection, for study and for experimenting with some of the old-fashioned navigational techniques.

It is supposed to be easy, nowadays, to know both where you are at sea and what you are most likely to bump in to.

But, as the fate of H.M.S. Nottingham shows - she was a British destroyer that whacked Wolf Rock, near Australia, in 2002 - the sea is still a very dangerous place.

In the eighteenth century, especially in the early years of that century, you never knew exactly where you were and you had very little chance of working out what you would bump in to from the primitive charts and navigational handbooks that were available. Explorers before Cook sailed round the world relying on the three Ls - 'lead, lookout and latitude' to keep their ships safe.

"Lead' - you swing the lead, dropping a lump of lead on a piece of string over the side of the ship, to find the depth. If the water is getting shallow very quickly, you try to go somewhere else immediately (if the wind happens to be in the right direction). But if you are approaching Boston (see Dana's great book, 'Two Years before the Mast',) you can navigate yourself into port in a fog by the samples of the sea-bottom that the tallow in a recess of the lead weight picks up and brings to the surface.

'Lookout' - while you are out at sea, you are safe (except from the elements) - it is the proximity of land which is frightening and brings you into the most extreme danger - so (if you are an old-time navigator) you post good lookouts all the time - especially when the water starts to get shallow. The lookouts can spot the tell-tale patch of cloud on the horizon that indicates a Pacific island, they can (if you are lucky) tell you when the colour of the water changes, which shows that you are getting closer to land; also, they can observe the type of birds that are seen, note the re-appearance of flies on board, maybe they notice a flying cockroach or catch a glimpse of a butterfly - there are lots of indicators that land is near that a good lookout can detect.

'Latitude' - from Phoenician times and certainly from medieval times, people knew that the Pole Star ('our star' as it is described in Dante's Inferno, written in 1320) was a good means of navigation.

It tells you where North is, in approximate terms, but also, if you measure or estimate its angle, it tells you how far up or down the globe you are, that is to say it establishes your latitude. People have relied on it as a basic indicator of geographical position for a very very long time. The sun at noon fulfils the same function, if you know how to use it, what allowances to make, which season (and which hemisphere) you are in.

Measuring angles is important for old-style navigation. It is the angle of the sun or of a star, in relation to the horizon or in relation to another heavenly body, which enables you to hypothesize where you might be, to make a well-informed guess about your vessel's whereabouts.

Whenever I get my sextant out on land, probably to check it, someone will always come up and make the jocular comment: "Where are we then? Know where we are?"

I try to be polite, but it always enrages me.

Sextants never tell you where you are. They are not like GPS at all - I love my sextant dearly but it is essentially a jumped up protractor just like the plastic gadgets children use at school but fabricated very accurately in metal and fitted with optics and micrometers and heavy filters to allow you to look directly at the sun - Sextants Measure Angles. That is all that they do.

What you do with the angles (afterwards) is up to you. You can use nineteenth century techniques (Sumner's position line/Marq St. Hilaire) which ought to allow you to calculate your position to within 2-5 miles from your true position or you can use the eighteenth century lunar distance methods that Captain Cook knew and Nevil Maskelyne (demonised as Harrison the Chronometer's worst enemy in Dava Sobel's book, 'Longitude') pioneered. This will give you your longitude "within a degree or a little more" as Maskelyne ventured in his introduction to "The British Mariner's Guide' published in 1763.

It will also take you hours and hours of patient calculation.

A degree is 60 miles at the equator. Maskelyne's method could, in his own estimate, produce a 'circle of uncertainty' around 75 miles wide, a vast improvement on the status before Maskelyne got to work, when the 'circle of uncertainty' could be hundreds of miles in diameter.

On the BBC voyage, my colleagues and I seem to have done rather better than Maskelyne predicted. Comparing the GPS positions of the ship with our estimates of its position after the journey showed that we were generally accurate to rather less than a degree. However, we had clear skies and very calm conditions.

On my second voyage on Endeavour, on the way across the Pacific, from Bluff, in New Zealand, to Cape Horn, Endeavour didn't see the sun or any star at all for 18 of the 39 days before we reached Cape Horn. We were also driven North (hove to) for a day and a half by a big storm. If I had been navigating by sextant and dead reckoning alone, I would have been a very worried man because it was impossible to tell, within a hundred or more miles, even what latitude we were on.

What have I learned? I have spent almost 12 months studying and working with eighteenth century ships and eighteeenth century navigational techniques. What have I proved or learned or established?

James Cook deserves his fame and his glory. His journeys are like the sculptures of Michelangelo - inimitable, unique, masterly, beautiful. When his men died from malaria, on the first voyage, he wrote about each of them as a friend; when his ship was in danger on the Barrier Reef, he records it in his journal with huge sang-froid and a professionalism which freezes my blood. He brought his ships and people home - not just on the first journey but then again on the second. His untimely death, on the third journey, was a sad and unnecessary tragedy - he was trying to prevent an escalation of a violent clash between the natives of Hawaii and his heavily armed supporters. But his men and his ships got home, even without him.

When Cook was 25 years old, his employer in Whitby (a Mr. Walker) offered him the opportunity to be the skipper of one of the colliers trading from Whitby to Newcastle and then to London. It was, I think, a good professional opportunity. Cook would have been secure and prosperous for life and he had started as a farm labourer's son with an apparent future just as a labourer or a shop-keeper.

Cook declined and joined the British Navy as an able seaman. He wanted to learn more about the world and he did. He taught himself surveying, navigation, seamanship, man-management. He saw himself as more than just a collier's skipper, more than just an ordinary person. He felt he had an important future in the wider world and he turned out to be right.

He was a great, great man and having, hesitantly and nervously, followed in some of his footsteps, I am more impressed than ever by his expertise, his energy and his capacity to endure.

The ship (the Endeavour replica) represents some of that and communicates some of it to you when you go on board.

Have a look at her, if you ever can - it is a wonderful experience. People like me, who have sailed on board, fall in love with Endeavour entirely and return repeatedly to find out more about her and about Captain James Cook.

It could be your turn next, to climb a mast or two, in gusty winds.

You won't ever forget the experience, if you do.

Captain Cook's return home is worth recalling in detail, in his own words.

Wednesday, 10th (July, 1771). Pleasant breezes and Clear weather. At 6 o’Clock in the Morning sounded, and Struck ground in 60 fathoms Shells and Stones, by which I judged we were the length of Scilly Isles. At Noon we saw land from the Mast Head, bearing North, which we judged to be about the Land’s End. Soundings 54 fathoms, Coarse, Grey Sand. Wind Westerly; course North 44 degrees East; distance 97 miles; latitude 49 degrees 29 minutes North, longitude 6 degrees 18 minutes West.

Twenty four hours later, they encountered "a fresh Gale, with which we run briskly up Channel."

Briskly indeed - I estimated his speed by his account of the landmarks on shore and it seems that Captain James Cook and his crew, the veterans of one of the great voyages, who should have been exhausted, debilitated, ravaged with scurvy, whose ship should have been falling apart and riddled with worm, covered the last 175 nautical miles in a magnificent 21. 5 hours - a speed of more than 8 knots. They probably had a big tide with them for more than half the time but it must still have been great sailing. Both foremast and main courses? The foremast topsail? Which of the spritsails? He doesn't say. Two strong men on the wheel - the ship flying home as if she wanted to, the deck bucking underfoot, everyone inwardly terrified and tearful and trembling with anticipation at the thought of stepping again, alive, having survived that epic adventure onto the soil of their homeland.

I think I now know something of how they might have felt.


THE END