ALL AT SEA JULY 2020
DOUGAL
on tour
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Solent based dinghy sailor David Henshall is a well known writer and speaker on topics covering the rich heritage of all aspects of leisure boating.
TIME AND TIDE (WAIT FOR NO MAN) Telling the time at sea, taken for granted by us all, was once a conundrum which took many years to resolve.
It then took even longer for him to finish the construction before, in 1736, Harrison and his clock made an outboard and return passage on HMS Centurion to Lisbon, where his clock continued to provide an accurate time. However, to win the prize, the competition had called for a voyage across the Atlantic, but in recognition of the progress that Harrison had made to date they awarded him a grant of £500. He used some of this money to fund a development of his sea clock, only to encounter yet more technical difficulties, but by now Britain was once again at war with Spain. His sea clock was considered so important that it would not be risked out afloat, with the fear of it falling into enemy hands and, just like on the clock itself, time would advance without an acceptable working solution. It would not be until 1761 that Harrison’s latest development made a trans-Atlantic crossing to Kingston, Jamaica, where, after 81 days at sea, it was found to be just five seconds slow.
T
he subject of navigation has been one of my popular, recurring themes in these pages. As everyone who goes afloat knows all too well, getting from A to B in a boat is fine when you can still look back and see where your departure point was and, at the same time, look ahead to where you are going. The moment you lose these reference points, plus any easy to see visual indications telling you where you are, life suddenly becomes a lot more difficult. Even a simple passage that takes you out of sight of land, either that “let’s go to sea” trip across the Channel, or even a coastal passage in poor visibility, can be fraught when the question of “where am I” has to be addressed. Today, of course, we have the wonderful accuracy of GPS that drives chartplotters, or even a programme on a high end smartphone to tell us where we are, but if we go back just a couple of hundred years, the lack of being able to pinpoint your location could have tragic results. VIKING VOYAGES Being able to calculate the latitude element of a position had been possible since the time of the great Viking voyages, who would lay their longboats beam on to the sun at the solar midday and then measure the length of the shadows cast. This was no more than a function of the height of the sun on any given day that visibility was good enough to allow a ‘sight’ to be taken. The simplicity of the Nordic navigational tools would in time be replaced by a whole range of measuring instruments, astrolabes and then, finally, by the marine sextant, with each development providing the navigator with an ever more accurate indication as to their position in terms of north and south. LOST FLEET However, with so many of the new possessions for the European nations on the far side of the Atlantic, there remained
the tricky issue of determining the position of a boat on the east-west axis. For the UK, boats heading homewards, and often driven by the prevailing brisk westerlies, knowing how long they had before they met the rocky shores that guard our western shores was becoming of prime importance. Apart from dead reckoning, the only real guide to navigators was the taking of soundings with a weighted line, as once the ocean depths started to be replaced by depths of less than 100 fathoms then the boats must be over the continental shelf, with land nearby. All these issues came to a head in 1707 when the British fleet, relying mainly on dead reckoning after days of poor visibility, ran on to the rocks to the south west of the Isles of Scilly, and in a matter of minutes four vessels, including the flagship HMS Association, had sunk with the loss of some 1,500 to 2,000 lives. At the subsequent inquiry it was found that although a previously undocumented current in the western approaches that had a northwards set (now known as Rennell’s current, which sweeps up from the Bay of Biscay) was a factor in the loss, the big issue was the ongoing problem of navigators not only being unsure quite where they were, but what the time was. PRIZE INCENTIVE The famous astronomer Edmund Halley (of Halley’s comet fame) applied himself to the question and determined that lunar observations could be used to determine longitude. Further work was done in the UK and in Europe to use what became known as the Lunar Distance method, but in the days before the publication of lunar tables in Marine Almanacs, the calculations of position were laborious and could take four hours to complete. What was needed was a mechanical way of telling the time on board ships, and with the increase in the frequency of marine trade and the value of the cargoes
The shortcomings of current navigation practice were laid bare on 22 October 1707 when the UK fleet, led by HMS Association, ran on to the rocks to the southwest of the Isles of Scilly. Close to 2,000 sailors drowned this became of the Navy’s worst peace time disasters.
that were being carried, the UK Parliament offered a prize of up to £20,000 (more than £3 million in today’s money). The difficulty was that the timepieces of the day, with the swinging pendulums needed to drive the mechanism, were totally unsuitable to the unstable platform of a ship at sea. There were those who thought that a sea born clock that would have to contend with the often violent movement, humidity and corrosive saline atmosphere was an impossibility, with none
other than Isaac Newton thinking that a clock was not the answer. WORKING DESIGN This did not stop many of the best innovators of the day from attempting to perfect the marine clock, but the technical issues were considerable. Just how difficult the problem was is shown by the fact it took until 1730 before John Harrison, a self-taught carpenter and woodworker, had a working design for his H1 ‘sea clock’.
A blunt and determined Yorkshireman, John Harrison would join the ranks of famous innovative Englishmen. Solving the technical issues of a sea-going timepiece would be almost easy when compared to his dealings with the British government! Image: NPG
TIME WOULD TELL In what would now be a shameful act, Parliament withheld the award of the prize money on a technicality, though they cheekily offered him a sum of £5,000 for the rights to his design. Further improvements to his design would follow, which attracted additional payments, though the promised prize money was never paid out to anyone. Harrison went to his death aggrieved, but nevertheless a wealthy man from his clocks, but his achievements cannot be overstated. The problems of the ship’s chronometer, and with it the resolution of not only time but also the longitude, were now sorted, resulting in a ship being able to know where it was at any given time. Today, even though we have a wealth of devices all telling a sailor the time, there are few boats that lack that all important ‘ship’s clock’, often co-located with the barometer, a continuing memorial to the incredible innovative efforts of John Harrison.
Isaac Newton said that it could not be done and that the on board movement, humid atmosphere and changes in temperature would prevent a clock from keeping time at All images: sea only for H2, Harrison’s clock, to prove him wrong. Image: DiscoverAndrew Scillies Wiseman