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    Re: Lunars - Finding Bermuda in 1807
    From: George Huxtable
    Date: 2007 May 13, 21:49 +0100

    Thanks to Frank for sending us young Basil Hall's account of his lunar
    longitude. That careful and interesting account was more that anyone has a
    right to expect from an 18-year old middie. It shows the degree of
    responsibility that could fall on one so young, and shows the care with
    which he discharged it, with the cooperation of the captured American
    captain.
    
    Perhaps he was aware of the tragic circumstances of the Anson
    circumnavigation, 70 years earlier, when a passage from Chiloe Island, off
    Chile, to Juan Fernandez Island, went so terribly wrong. Anson's plan, and
    his dead reckoning, aimed to put him West of the Island, so he could turn
    East when he reached the right latitude, then sail down the latitude until
    he reached Juan Fenandez. Unfortunately, when he turned East, the ocean
    current had already taken him East of the island, so when he turned East, he
    was sailing away from it. He discovered that, two days later, when he saw
    the Andes mountains in the distance. It took another week to beat back to
    the island, in which time, another 80 of his crew had died of scurvy. The
    Erin was facing somewhat similar dangers, and both Hall, and the American
    captain, would have been desperate to avoid it.
    
    I ask Frank to give us references to that Basil Hall text, and his other
    works that he mentions. I haven't come across him before, and judging by
    that story, I need to put that right.
    
    I wonder how Frank produced that nice email text for us. Was it transcribed
    longhand, which would have been quite a lot of work. Or has it already been
    converted to machine-readable form, perhaps by OCR?
    
    It's an admirably clear account, and there's just one aspect that puzzles
    me. His first round of lunars was taken just after sunset, until the horizon
    became too faint to admit of the altitudes being taken with accuracy, he
    tells us. Then he worked out those lunars to get his longitude, discussed
    and cross-checked them with the captain, went back to take another round,
    worked out and cross-checked his lunars once again. So, for that second
    round, how did he get the necessary Moon and star altitudes to clear the
    lunar distance, as by then the horizon had long gone?
    
    I am aware that the job can be done by computing, rather than observing the
    necessary altitudes, but it's a complex business, and involves a certain
    amount of iteration. If that second round had to be computed by such a
    different procedure, I would have expected the navigator to make something
    of it, as another feather in his cap.
    
     The computations, between the two of them, must have been done very
    expeditiously, for those two rounds to have been worked out and a course of
    action settled in time for the new course to be steered around midnight.
    
    Incidentally, there's a curious turn of phrase, to my ears, in the Hall
    writes that he "bore up", and "spanked along merrily toward the Wast". In my
    book, that would be bearing away, not bearing up. Do others agree?
    
    Finally, worth noting is Hall's statement-
    
    | All the ordinary
    | allowances for the set of he Gulf Stream had already been made, and it was
    | hardly to be conceived that in a week or ten days there should have
    occurred
    | an error of a degree and a half.
    
    Well, at the latitude of Bermuda, a degree and a half is only about 76
    miles, so that statement shows an extraordinary self-confidence (or perhaps
    naivety) in presuming that such an error could not accumulate in 7 to 10
    days of dead reckoning.
    
    George.
    
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message -----
    From: 
    To: 
    Sent: Sunday, May 13, 2007 2:32 AM
    Subject: [NavList 2871] Lunars - Finding Bermuda in 1807
    
    
    |
    | Greetings, Fellow Lunatics.
    |
    | As a preamble, I will note that June 22, six weeks from now is the 200th
    | anniversary of a naval encounter known to historians as the
    | Chesapeake-Leopard incident in which HMS Leopard fired upon the American
    | frigate Chesapeake after insisting on the right to board her and search
    for
    | British deserters. The commander of the Chesapeake surrendered his vessel
    | after scarcely any resistance. The British commander refused the surrender
    | and boarded as originally intended, taking away a few sailors, one of whom
    | was later hanged for desertion from the Royal Navy. There was considerable
    | outrage in Washington over this incident, both the boarding and the swift
    | surrender of the Chesapeake, but at the time, it was only a "seed" for the
    | upcoming war, known today as the War of 1812.
    |
    | Later that same summer, in mid-August of 1807, HMS Leopard stopped another
    | American vessel, the Erin, a small, fast merchant vessel transiting from
    | Bordeaux to Baltimore in defiance of the British blockade of Napoleonic
    | France. The navigational details of this particular incident were
    described
    | in detail by Basil Hall, at that time an 18-year-old midshipman who was
    | placed in command of the Erin as "prize-master" and ordered to take her to
    | Bermuda for adjudication.
    |
    | Basil Hall wrote a series of books describing life in the Royal Navy in
    the
    | early 19th century. These books were an important resource for Patrick
    | O'Brian and apparently provided much of the period detail in his novels. A
    | few of Basil Hall's books are available on googlebooks. The one which I
    | quote below in not among them but there are portions of it quoted in yet
    | another book.
    |
    | Here is Basil Hall's story of lunars in 1807:
    | "When I was mate of his majesty's ship Leopard, I was placed in charge of
    | the identical ship which carried Jerome Bonaparte and his family to
    Europe,
    | and selected for that purpose from being considered the fastest sailer out
    | of Baltimore. I certainly never saw a more perfect model of a merchant
    | vessel or one more commodiously fitted up. I was, of course, prodigiously
    | proud of my new and beautiful command; but had soon more important matters
    | to attend to in the navigation of the ship.
    |
    | "When we parted company with the Leopard, we were within a few days' sail
    of
    | the coast of America, and may then have been a hundred leagues or so to
    the
    | north-westward of Bermuda; consequently, still within the influence of the
    | Gulf Stream, already alluded to as sweeping, in a north-eastern direction,
    | along the shores of the United States. I was ordered to take my pretty
    | charge to Bermuda and proceeded to the southward accordingly. Foul winds,
    | however, detained us for several days in the Gulf Stream, for the set of
    | which current such an ample allowance was made, that when we reached the
    | latitude of Bermuda, 32 1/2 N., it seemed almost certain that we were some
    | thirty or forty miles to the westward of the island, that is between it
    and
    | the coast of America.
    |
    | "From the land of Bermuda being low, it is not easily got sight of; and
    the
    | whole cluster of islands beging of small extent, they are often missed by
    | navigators steering, as they conceive, directly for them. To those,
    indeed,
    | who are provided with time keepers, there is no danger in following this
    | direct method; for these instruments are now so admirably constructed,
    that
    | an error in longitude which would carry a navigator past Bermuda, without
    | seeing it, is, now-a-days [Hall is writing in the 1820s], very unlikely to
    | occur. Ships, however, which have not the advantage of a chronometer, and
    | consequently may not be sure of their longitude, generally find it prudent
    | to run into the latitude of the island, and then steer along that parallel
    | till they come in sight of their object. Most people are probably aware,
    | that the latitude is an element of navigation almost at all times very
    | easily determined, at least with sufficient accuracy for the purpose now
    | alluded to. The longitude, as every mortal must have heard, is, or rather
    | was, the grand stumbling-block in a sailor's way; and it will readily be
    | understood, of what essential importance it must be to a ship, when
    running
    | along a parallel of latitude, in search of a mere speck on the ocean, like
    | Bermuda, that there should be no mistake as to which side of the island
    she
    | really is upon. For if, in point of fact, the ship shall happen to be on
    the
    | eastern side of the island, but, owing to some error in the reckoning, her
    | captain believes that she is on the western side, he will naturally steer
    | east along the parallel of latitude, instead of west, as he ought, of
    | course, to do; and thus will go on increasing his distance from the
    island,
    | instead of shortening it.
    |
    | "This curious case was precisely mine. The Gulf Stream, as it eventually
    | appeared, had carried us eighty or ninety miles farther to the eastward
    than
    | I had made allowance for, although an ample daily set in that direction
    was
    | given her. The superficial velocity of this mighty current, it seems, is
    | occasioneally accelerated or retarded by the prevalence of hard gales. At
    | all events, whatever might be the cause of this unusual increase in the
    rate
    | of the stream, it carried me so far beyond my mark, that when I reached
    the
    | parallel of 32 1/2 N., I supposed myself in longitude 65 1/2 W., that is,
    | about forty miles on the western or American side of Bermuda. As the wind
    | was blowing from the east, of course I struggled hard to beat up against
    it,
    | from supposing that my port lay to windward. It was fortunate that this
    | breeze was not blowing from the west, as I shall proceed to show.
    |
    | "On the day I reached the latitude of Bermuda (32 1/2 N.), I fancied the
    | ship must certainly be on the western side of the island; the sun, however
    | happened not then to be in distance, as it is called, and, of course, no
    | lunars could then be observed. Having, therefore, still nothing to trust
    to
    | but the dead reckoning, we, of course, continued beating all the morning
    to
    | the eastward, under the full persuasion that Bermuda was in the wind's
    eye,
    | due east of us, instead of being, as it really was, due west, on our
    | lee-beam.
    |
    | "As the night approached, the sky became beautifully clear, and shortly
    | after sunset I got my sextant to work. Before the twilight was ended, and
    | the horizon too faint to admit of the altitudes being taken with accuracy,
    I
    | had observed four or five sets of lunars. No time was lost in working out,
    | when, lo and behold! the longitude, instead of being 65 1/2 W., as I made
    it
    | by dead reckoning, appeared to be little more than 64 W., or some ninety
    | miles farther to the eastward; thus showing that, although, as we
    supposed,
    | we were thirty miles from the land it was on the opposite side of the
    island
    | from that on which we had imagined ourselves to be!
    |
    | "What was now to be done? For, although on board the flag ship, where the
    | accuracy or inaccuracy of a midshipman's lunars did not matter a straw, I
    | had indulged in the usual presumption of fancying myself rather an expert
    | observer, I was now filled with doubt and anxiety. All the ordinary
    | allowances for the set of he Gulf Stream had already been made, and it was
    | hardly to be conceived that in a week or ten days there should have
    occurred
    | an error of a degree and a half. It appeared far more likely that some
    gross
    | mistake had been committed in the figures of the computation, or in my
    mode
    | of observing the lunars, than that such a huge augmentation to the
    strength
    | of the current should have occurred at this particular moment.
    |
    | "The American captain, who, like most commanders of ships of that class
    | sailing from the United States, was an admirable navigator, and a very
    | shrewd, obliging, and gentlemanlike person, happened to be so ill that he
    | could not possible come on deck, to make observations to corroroborate
    mine.
    | But he was able, though in bed, to go over the computations, the result of
    | which, in his hand, agreed so nearly with what I made it, that he, at
    least,
    |had no doubts of their accuracy, and recommended me at once to put the helm
    | up, and steer to the westward. I had not confidence enough, however, in my
    | own handiwork, for a decision so material to the success of the voyage. In
    | short, I could not force my unpractised imagination to conceive that an
    | island, which I had so much reason to suppose lay due east of me, could
    | possibly be hit upon by steering due west.
    |
    | "So, to work I went again, with my observations for the longitude. After
    all
    | the adjustments of the sextant had been carefully examined, a new gang of
    | lunars was taken, some with the same, and some with other stars, but all
    of
    | them with a degree of attention which, if measured by the depth of
    interest
    | felt in the result, I am not sure I have ever bestowed upon any similar
    | course of observation since. Half of the distances I gave over to my
    friend,
    | the captain, to compute, while I set about calculating the rest. After a
    | time we exchanged computations, without communicating each other's
    results,
    | till all were finished, and then we laid them side by side. The agreement
    | amongst the whole observations was so near to one another and corresponded
    | also so closely with those taken earlier in the evening, that I could no
    | longer have a doubt as to what should be done. About midnight, with a
    | throbbing heart, and a mind filled with the most painful anxiety, I bore
    up,
    | and, as we had a fresh breeze, spanked along merrily to the west. It was
    | necessary, of course, in running in such a perilous neighborhood, to keep
    a
    | very bright look out; for although Bermuda, on its eastern side, is pretty
    | clear of coral reefs, and we were quite certain of our latitude, it was
    not
    | the sort of place to approach incautiously. When the moon went down,
    | terefore, we shortened sail, but continued still slipping along at the
    rate
    | of four or five knots, till morning.
    |
    | "When the eastern sky first began to give some faint promise of a dawn, I
    | felt my anxiety mount to a pitch scarcely bearable, and I kept peering
    with
    | the night-glass into the gloom which still hung over the horizon in the
    | supposed direction of Bermuda, as if my eagerness to see what was hid
    | beyond, could have brushed away the night any quicker. When, at last, the
    | day broke, and the well-known cliffs of St. David's Head, topped with dark
    | green cedars and lighter-tinted orange trees, stood pleasantly up ahead of
    | us, at the distance of a league and a half, I could have shouted with joy.
    |
    | "I was not a little amused by finding we had reached the island before our
    | own ship, and, a few days afterwards, I had the satisfaction of rowing on
    | board to report myself, before she anchored. The compliments paid to our
    | success were due, it must be owed, to the sextant so opportunely sent to
    me
    | for, unless the dead reackoning had been checked by lunar observations, we
    | might have been kept at sea a month; and, as the ship was short of
    | provisions, serious consequences must have ensued."
    |
    | And that ends Basil Hall's account of these events. It's interesting that
    | Hall did not give more details regarding the American vessel he was
    | commanding. He did not name it in his book. I asked on H-Maritime (a
    | low-volume maritime history list) if anyone knew the name and found soon
    | enough that it was the Erin. With that clue, I discovered several other
    | fascinating references through google books including a short article
    | written in 1919 providing some details ("An Early Baltimore Clipper: the
    | Capture of the Erin"), and a letter written by the British Consul in
    | Washington in March, 1805, when Jerome Bonaparte sailed with his young
    | American wife from the US to Lisbon. From that letter, we have this
    | description of the Erin: "She is a fine small Ship, sails very fast,
    bright
    | sides, white bottom, black Wales, yellow Gun wale, dead eyes yellow, no
    bull
    | work a midship, and a figure head". I can almost see her now... She was a
    | vessel of 213 tons and unusually fast, typical of the Baltimore Clippers
    | which would soon become famous as privateers and traders and infamous as
    | slavers. The Erin had previously served as a diplomatic courier for the
    | Spanish between Europe and the Caribbean. Just before the events Basil
    Hall
    | desribes, she had left Bordeaux with a cargo of brandy, wine, and dry
    goods
    | on June 26, 1807 and was detained by HMS Leopard on August 13, 1807. The
    | captain, whom Hall speaks of so highly, was William Stevenson. The lunar
    | observations described by Hall must have taken place on the night of
    August
    | 20-21, 1807, give or take a day. As he says, the Sun was "not in
    distance",
    | so he was compelled to se the stars for lunars, apparently much less
    popular
    | among practical navigators.
    |
    | I think this story is a nice example of the transition from dead reckoning
    | navigation to celestial navigation. Hall clearly believed rationally that
    | lunars worked, but this was an era when navigators had great faith in dead
    | reckoning. They trusted it, and it took a revolution in their thinking to
    | trust sextants and mathematical tables more than the log and the feel of
    the
    | sea.
    |
    | -FER
    | www.HistoricalAtlas.com/lunars
    |
    |
    | |
    |
    
    
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