Welcome to the NavList Message Boards.


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

Compose Your Message

Add Images & Files
    Re: Slocum's lunars
    From: Herbert Prinz
    Date: 2003 Dec 13, 11:11 -0500

    Jan Kalivoda wrote:
    > The explanation of the expression "the greatest science" as a guess of the
    > longitude from crossing the border of two distinct currents off the coast
    > (or a guess of the effects of the stream and the wind effects for DR in
    > general) seems to be exaggerated by Frank. It is undoubtely the great
    > navigational skill and "art", but a sort of science? Maybe, Slocum had
    > understood this word in this sense, but I doubt.
    I don't  consider this unlikely at all. The terms "ars" or "art", "Kunst", etc.
    have been commonly used in books that were of a nature that we would nowadays
    call "scientific". Conversely, as the word "science" came into a wider use
    during the 19th century (parallel with the profession of "scientist"), it was
    only natural to use it for _all_ the contents that was formerly described in
    those "art"-books. In other words, for Slocum "art" and "science" were synonyms.
    > Slocum's mention about the error in logarithmic tables cannot be explained
    > as a hint at his own error, which he sought to hide by pretext of erroneous
    > tables. Such tricks are common for beginners that failed the resolve the
    > task, but Slocum wasn't a beginner and he resolved his task of these unique
    > clearly attested lunars very precisely after all near Nukuhiva (if he isn't
    > a liar in your eyes).
    Not necessarily the trick of a beginner, but maybe a repression of his
    embarrassment; the reaction of somebody who should know better, but who's skill
    got rusty. Most puzzling about this is that he resolved the problem so easily.
    How on earth could he correct a faulty table of logarithms out there alone and
    without resources?
    First he re-took the observation. This was very reasonable. But next he went
    straight to the tables to look for a discrepancy. I would have verified my
    computation first. Either he was so confident in his that he did not see a need
    to check it; or he could not check it beyond repeating every step, because he
    might just have mechanically followed a procedure without really understanding
    its particulars. However, let's give him the benefit of the doubt and assume
    that he just does not tell us in his narrative about this important step.
    Searching for "a discrepancy in the tables, [he] found it. In the tables [he]
    found that the column of figures from which [he] had got an important logarithm
    was in error." Not an individual logarithm was in error (which could have been
    corrected easily by interpolation from adjacent values), but a whole column.
    Now, he does not say that he bypassed the erroneous table entries (for instance,
    by choosing an alternative reduction method, or by consulting an other set of
    tables), but he claims to have corrected the faulty ones. That's quite a feat!
    Likely, we are talking about reduction tables and not the almanac, because
    Slocum says "tables". The only logarithm in the almanac is the proportional log.
    of the difference of the distance. Funny thing, we have never heard about Slocum
    contributing corrections to published tables. I do not want to make an
    argumentum ex silentio as has been done before in this discussion, but I think
    that some research into contemporary tables could be beneficial here. Maybe one
    pops up that has a whole column of wrong logarithms.
    In the mean time, the assumption that Slocum misunderstood a table heading, an
    instruction, or some such thing, picked first the wrong column, and afterwards
    the correct one seems like a good working hypothesis to me.
    Herbert Prinz

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    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 Settings

    Posting Code:

    Custom Index

    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