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
    Name or NavList Code:
    Email:
       
    Reply
    Re: Navigational instruments at the Naval Museum in Lisbon
    From: Jürgen Hoefeld
    Date: 2010 Feb 25, 23:34 +0100
    By the way, the Davis quadrant  http://www.fer3.com/arc/imgx/IMGP5954.JPG  labelled: 'Elton's quadrant replica' seems to be no Elton quadrant at all but an ordinary Davis quadrant. I can't see any bubble or levelling attachment.
    This brings me to some more questions on diagonal scales on Davis quadrants:
    • The sight vane on the 30° scale of a Davis quadrant has to be proper aligned with the horizon vane to get a meaningful reading on the transversal scale on the large arc. Otherwise the reading of minutes on the diagonal scale is meaningless.
    • How did the manufacturers and/or users ensure this alignement?
    • What is the oldest existing Davis quadrant? I only found examples which are not much older than the first octants from the 1730s, compared to Davis publication of 1595.
    • Does anyone remember having seen in a museum or collection an existing Elton Quadrant like that  by made by Sisson in the  Phil. Trans. 1731-1732, vol. 37, 273-279, depicted in http://en.wikipedia.org/wiki/File:Elton-quadrant.jpg or on John Vanderbanks painting http://www.nmm.ac.uk/mag/pages/mnuExplore/PaintingDetail.cfm?ID=BHC3128  in the National Maritime Museum?
    I am looking forward to your hints.

    Best regards,
    Juergen Hoefeld
    Aachen, Germany


    2010/2/25 Douglas Denny <douglas.denny@btopenworld.com>

    Ah! but which came first the chicken or the egg?

    Or, in this case: is 'Gunwhale Circle' a simple error by whoever wrote the label due to the fact a 'Borda Circle' (so called because of the inventor) has the same name in Portugese? It could be as simple as that.

    I think your extrapolation needs further evidence of the use of a term like 'Gunwhale Circle' being in actual use by Portugese sailors contemporaneously with the use of the circle itself in the nineteenth century.

    I have come across simple blunders in labelling in museums before where it is obvious the person who wrote the label did not 'know his onions'.

    Douglas Denny.
    Chichester. England.


    ----------------------------------------------------------------
    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?

    Get a NavList ID Code

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

    A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.

    Retrieve a NavList ID Code

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

    Email Settings

    NavList ID 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