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    Re: Biruni and the radius of the Earth by dip
    From: George Huxtable
    Date: 2011 Jan 4, 21:48 -0000

    Since I posted the following, in the early hours of this morning, there
    have been three postings on the Biruni topic, none of them referring to
    that text.
    I think I have found what John Huth is seeking, though I haven't really
    read it yet. It's at-
    It's ref 37 in the Wikipedia page on Biruni,
    Gomez, A. G. (2010) 'Biruni's Measurement of the Earth', Journal of
    Scientific and Mathematical Research.
    I've no idea whether it's worthwhile or not.
    That recent paper deals with the question of refraction, and claims to have
    identified the mountain used for the observation, in the Himalayan
    foothills South of Rawalpindi, and provides a profile of the plain below
    it, to the South, between the Jhelum and Chenab rivers, which was claimed
    to suffice in place of a sea-horizon.
    There are several curiosities, including the notion that with an astrolabe,
    one might measure a dip of 34' to the nearest minute. All astrolabes that I
    have seen have been divided to whole degrees, no finer, and the sighting
    and levelling arrangements are remarkably crude. It seems clear that any
    similarity between the true radius of the Earth and Biruni's result can
    only have been accidental.
    I suggest that anyone making pronouncements about Biruni's procedure should
    first take a look at the Gomez paper.
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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