Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Old question - need summary
    From: Frank Reed
    Date: 2010 Oct 31, 21:13 -0700

    John, you wrote:
    "I naively thought [the Shovell disaster] was in part responsible for the Longitude Act of 1714"

    That's not naive. It was unquestionably responsible "in part". Then again, a certain mathematician getting booted out of the Lucasian Chair at Cambridge over some mildly eccentric attitudes with respect to Christianity and seeking to regain his fortune and fame were responsible "in part"...

    And you wrote:
    "Yes, I found that Ushant and the Scillies were separated mainly by a latitude difference. "

    Aha! Latitude, not longitude. D'oh!

    Don't fall for it, John. :-)

    The references to Ushant in the Shovell disaster appear to arise in the middle of the 19th century. The idea of the navigators from all the vessels assembling for a conference seems to originate about the same time. They are not part of the original story. In fact, the logbooks (from 1707) don't show the vessels "off Ushant" at all, according to May. So where did they think they were? First, they mostly thought they were near the latitude of the north side of the Channel, though that, too, is relatively uncertain. That's where they wanted to be, right? They were at war with France at the time, so more towards the north side but not too near the north side would make good sense, and that's what the logbooks appear to show. As for longitude, by their actual "reckoning", meaning the dead reckoning or longitude "by account", they really had no idea where they were across a range of hundreds of miles. In May's paper from fifty years ago, he presented a theory including a map he commissioned that shows the longitudes clustered rather close to the longitude of Scilly, but this depends on a particular choice for the difference in longitude between their point of departure, Cape Spartel in Morocco (if I remember correctly), and locations in southern England. Those differences disagreed greatly one from another in published sources, so the actual uncertainty in longitude is much greater than displayed by May's diagram. That's the status of the dead reckoning alone, but Shovell had more to go on than "pure" dead reckoning. He also knew that they were in soundings and presumably he had even seen the mud pulled up stuck to the tallow. Those soundings, while quite deep, pin down the longitude considerably better. On a modern chart, we can follow the contours of the soundings and mark the position of the fleet with some accuracy. If we knew where Shovell believed that the 80/90 fathom band was located, based on his nautical information back in 1707, then we could narrow down better his estimation of the fleet's position. But this was highly uncertain information. The surveys themselves suffered from the same navigational uncertainty, especially with respect to longitude, as did the navigators of Shovell's fleet.

    You wrote:
    "From what I could tell, blaming this on a solely on a lack of knowledge of longitude is a gross oversimplification and is a bit suspect."

    The inability to determine longitude accurately was a major factor, as it always was in this period. But of course, the Scillies are an island group with basically one longitude, one latitude (at the map scale where the group is a dot). So to hit the Scillies you necessarily have to involve both coordinates. On the other hand, there are dangerous headlands and rocks all along the southern shore of Cornwall and England.

    For me, the best evidence is the evidence of the sailing orders. Shovell was a competent, respected commander and no fool (very much contrary to mid/late-20th century accounts including, but not limited to, Sobel's "Longitude"). He gave orders to sail, in the dark, with a strong wind blowing, on a course somewhat north of east. This much is known from the surviving logbooks. Where would such orders make sense? If YOU were going to sail for some twelve hours in the dark on that course, where might you believe yourself to be? It's certainly not something you would do if you believed yourself "off Ushant" and close to the coast. Nor would you give those orders if you believed you were ANYWHERE near a dangerous coast. That narrows things down a bit. Either Shovell believed very strongly that his fleet was smack in the middle of the channel or its opening, just about halfway between Scilly and Ushant, and therefore the disaster was an error of latitude, or Shovell believed that he was still a considerable distance out to the west, and therefore the disaster was primarily an error in longitude.

    In the early 18th century, the accident was initially blamed by the Royal Navy on compasses, or in other words, bad dead reckoning. This is the sort of intentionally myopic answer that boards of inquiry generally produce. They find the immediate cause. For a more modern example, consider the conclusion of the investigation of the Apollo fire in 1967 which concluded that the cause of the accident was frayed wires and a spark. Sure, the spark set it off, but only after so many things had gone wrong up to that point. It sure wasn't the real cause. In the Shovell disaster, the immediate blame could be placed on the poor quality of the compasses and the mediocre results of the dead reckoning, but anyone who knew the principles of navigation in that era recognized that a proper means of determining longitude was the essential piece of the puzzle that was missing. It was the "big picture" problem, the Holy Grail of navigational science.

    By the time of the proposal for the Longitude Prize in 1714, the Shovell disaster, specifically, was directly connected in public discourse with the problem of longitude. William Whiston, who had succeeded Newton to the Lucasian chair but then lost the job thanks to his very slightly heretical views on religion, had discovered a solution to the problem of longitude with his partner Humphrey Ditton. They sought the support of England's merchants and mariners by publishing their certain belief that their solution would have saved Shovell and his fleet of warships and the 2000 lives and 100,000 pounds in treasure that were lost that night. In the list of a dozen reasons published by Whiston and Ditton in support of the Longitude Act, they wrote:
    "X. Because it will prevent the Loss of abundance of Ships and Lives of Men; as
    it would certainly have sav'd all Sir Cloudesley Shovel's Fleet, had it been
    then put in Practice."
    When Parliament passed the Longitude Act it was primarily based on their pleading and the support, albeit half-hearted, that they won from Isaac Newton. That's the direct line from Shovell to the problem of longitude.

    But there's a catch in all of this. The method of Whiston and Ditton was a method of finding position by ranges from stations with known positions, like an early, primitive Loran. So although it was sold to the scientists (and sold "by" the scientists as well) as a solution to the problem of longitude, it was simultaneously a solution to the problem of latitude. So Whiston and Ditton's item ten quoted above still holds true even if Shovell's fleet was not destroyed specifically as a result of an error in longitude. As we know, the Whiston and Ditton proposal was eventually considered to be unworkable for many reasons, and the two of them soon suffered the scathing mockery of Swift and many others.

    The Shovell disaster and its causes drop right off the map for nearly a century, little more than a tragic footnote in naval history. Yet it's still understood to be connected with the Longitude Prize and the development of the chronometer. In a charmingly symbolic act, near the end of the century, one of Britain's best navigator-surveyors went to the exact location of Shovell's temporary grave on the beach in the Scillies and carefully measured its longitude using a fine chronometer as his source for Greenwich Time. To add to the irony of the story, he also found that the LATITUDE of the Scillies was STILL incorrectly plotted on British charts at that time.

    In the early 19th century, the story of the Shovell disaster becomes popular again when versions of it were recorded by travelers visiting the Scillies. The idea that grass would not grow on his temporary grave is typical among these. There also emerged a story about some young sailor frantically announcing that they must be near the Scillies because he could smell the seaweed fires that the locals used to make fertilizer. Since he and all but one survivor of the crew of the Association were drowned a few hours later, there is, of course, no way to validate this tale. But we do know that it was told within a year or two after the disaster. Nor is there any way to prove that this doubting sailor was hanged for insubordination, or otherwise. The navigational clue suggested in the earliest versions of the story, namely a unique smell from the land, is just the sort of navigational skill that scientific navigation eventually erased from western navigational knowledge. By the end of the 19th century, the story had been modified to suggest that the doubting sailor was "keeping his own reckoning". That's very unlikely (and irrelevant in any case --why would it be any better than anyone else's?), but by then the idea that a smell in the air might have been navigationally decisive probably sounded like fantasy.

    In the twentieth century, the whole tale stabilized and was widely told in just the same fashion as told by Dava Sobel in "Longitude". For a specific example, here is how the story of Shovell and its connection to longitude was related by astronomer and historian D. Fernie back in 1974:
    After describing the general problem of finding longitude at sea, he wrote,
    "Meanwhile more and more ships ploughed the seas in dismal ignorance of their positions. Not only were valuable cargoes forever being lost in shipwrecks, the toll in lives was appalling. There was Sir Cloudsley Shovel, for instance, returning to England from Gibraltar in 1707 and running into heavy weather. His navigators all agreed the fleet was off Ushant, although an ordinary seaman had the temerity to advise his superiors that he reckoned otherwise. While he was being sentenced to swing from the yardarm for his mutinous attitude, the fleet sailed in accordance with the navigator's decree, ran head-on into the Scilly Isles and lost four ships and two thousand lives, Sir Cloudsley's among them. Some solution had to be found."
    I posted this previously for NavList just about three years ago.

    This telling by Fernie is obviously very nearly identical to the account in Sobel's "Longitude", and it's also nearly identical to the first version of the Shovell disaster which I first read back in 1979 or so when I was working as a teenage planetarium lecturer at Mystic Seaport. The article above by Fernie is NOT the exact version that I read --there were plenty of variations on that basic theme. The whole thing was standard throughout the second half of the twentieth century: the navigators "all agreed the fleet was off Ushant" and "an ordinary seaman" who is "sentenced to swing" and the over-arching message that this was caused by a failure to know longitude and that a "solution had to be found". NONE of this was invented or fabricated or naively believed by Dava Sobel, as a few modern readers have mistakenly suggested. This was the widely-recognized, common account of the disaster and its implications amonhg historians of science. Sobel's version, of course, also includes fictionalized "color" and dialogue. This was a popular style of fictionalized non-fiction literature in the 1990s (see also the similar style in this respect of Junger's "The Perfect Storm"). Unfortunately, this has led to some outlandish further embellishment in derivative works like the version with an almost crazed Shovell at the opening of the mini-series version of "Longitude". That's tv.


    -FER
    PS: The link to the book transcribed here: http://www.hmssurprise.org/Resources/SIR_CLOUDESLEY_SHOVELL.html
    which George Huxtable says he had never seen before has been posted to NavList at least twice before (by me, in May, 2006 and September, 2007 see: fer3.com/x.aspx/03192). It has also been available on Google Books for nearly four years here: http://books.google.com/books?id=LSKyXvK0bEMC. Memory is a fickle thing. Thank goodness for searchable archives.


    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site