A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2019 Jan 15, 12:04 -0800
Don Seltzer mentioned Basil Hall and Bermuda. I haven't thought of that in a while! Yes, it's a good story.
In the early 19th century, during the Napoleonic Wars Royal Navy vessels policed the Atlantic and frequently stopped and boarded American merchantmen. In mid-August of 1807, HMS Leopard stopped an American vessel, the Erin, a small, fast merchant vessel transiting from Bordeaux to Baltimore in defiance of the British blockade of 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, sometimes long verbatim quotes (unattributed usually... but hey, they were novels! That's allowed).
Here is Basil Hall's story of lunars in 1807:
My comments in square brackets, [like so].
"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 being 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 [this was a common name for chronometers until about 1810-15], 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 [not often true in practice, but it's what most navigators believed]. 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 occasionally 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, therefore, 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 reckoning 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. A little digging turned up the name "Erin". With that clue, I discovered several other fascinating references 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 describes, the Erin 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 17, 1807, give or take a few days (some of the astronomical details don't seem to add up, but I suppose that's a result of writing a memoir many years after the events). As he says, the Sun was "not in distance". This was Full Moon or nearly, so he was compelled to use the stars for lunars, apparently much less popular among practical navigators. It's likely that Basil Hall shot Moon-Antares lunars on that first night, but he mentions he tried other stars, too. There were planets aplenty in the evening sky, but in this era, lunar distances were not tabulated for the planets.
The "moon in distance" was an expression lunarian navigators used specifically for those convenient cases when the Moon was near First Quarter or Last Quarter, about 90° away from the Sun. From the almanacs and the navigation manuals, like Bowditch, you would get the erroneous impression that stars were just as popular as the Sun and that any lunar distance angle would be used. But primary source evidence tells a different tale. Lunars were shot when the Moon was "in distance" with the Sun in the majority of cases, and with good reason.