NavList:

Some years ago I was doing some research into the first American squadron deployed to the Mediterranean for the Barbary Wars.  It arrived at Gibraltar on 1 July 1801. Captain Bainbridge of the Essex wrote the following in his journal:

At 7 am fell in with three French sail of the line, two Eighty four
guns & one seventy four
- The Admiral [Linois] sent his boat on board the Commodore [Dale].
At 8 AM spoke the Commodore, he ordered me to lead into Port & Anchor.
At 1/2 past 9 came to anchor in the Bay of GIbraltar in 15 fathoms
water & with the following marks,
Europa point  S 16º E
New Mole    N 30º E
Cabaretti Point  W 20º S
South signal tower  E 46º S
Algeziras     W  25º  N

This is a fascinating moment in naval history. French Admiral Linois and his squadron were just outside the Bay of Gibraltar on the morning of July 1, struggling west through the Strait against a contrary wind, trying to reach the Atlantic. There were few Royal Navy ships at British held Gibraltar, with most of the fleet at Cadiz. Messages were dispatched overland to warn British Admiral Saumarez of the danger. Readers of Patrick O'Brian will recognize this moment in history. Two days later at dawn, Linois comes upon Cochrane and the brig Speedy. After the capture, Linois turns back to the Spanish port of Algeciras, just across the bay from Gibraltar, arriving the next day and setting the scene for the subsequent Battle of Algeciras when Admiral Saumarez arrives with the British squadron and immediately attacks the French. In the meantime, the American squadron is anchored just beyond the battle, as neutral observers of a major battle developing.

Now to the navigational aspect.

I was curious as to just where Bainbridge and the Essex were anchored. So I searched for a late 18th century chart of Gibraltar Bay, and began drawing the bearing lines from Bainbridge's journal. Europa Point marks the eastern opening to the bay, and Cabaretti Point the western. Algeziras, where Linois anchored his squadron is across the bay on the western shore.

My first effort was discouraging. Some of the bearing lines intersected over a broad area just outside the bay, and the bearing for Europa Point was just impossible. I wondered if the transcription was correct, but then I realized that Bainbridge would have taken these readings with his azimuth compass. The bearings were possibly for magnetic North, and uncorrected for magnetic variation.

So what is, or rather what was the variation for Gibraltar in 1801? I found that variation has changed radically over the centuries, and in 1800, the variation for Gibraltar was nearly 20º West of true North. So I plugged in the corrected numbers, and the bearings for Europa, Cabaretti, and Algeziras intersected nicely on the eastern side of the bay. Only the bearing for the New Mole was badly off. But Gibraltar also had an Old Mole in 1801, further north. I drew a new line through that location and bingo! All the lines neatly intersected at an anchorage just offshore of Gibraltar.

Don Seltzer