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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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