On Tue, Apr 7, 2020 at 12:24 PM Michael Ossipoff <[email protected]> wrote:
> ...and of course the surrounding flat-dials could, instead, be > Reclining-Declining Dials facing in the cardinal-directions. > > But the sphere-segment indentation surface gives a better continuous > system of dial-lines. > > On Tue, Apr 7, 2020 at 12:18 PM Michael Ossipoff <[email protected]> > wrote: > >> If the indentation were a shallow rectangular hollow instead of a segment >> of a sphere, it would of course amount to several adjoined flat dials--a >> horizontal-dial surrounded by vertical-dials. >> >> Michael Ossipoff >> 16 Tu >> Aries 19th >> Aprilis 7th >> >> On Tue, Apr 7, 2020 at 7:07 AM Peter Mayer <[email protected]> >> wrote: >> >>> Hi, >>> Dan-George Uza's recent post reminded me of a question I have. I was >>> looking at Mark Lennox-Boyd's lovely *Sundials* the other day, >>> especially photos of some of the beautiful Renaissance ivory diptychs, and >>> realised that I didn't understand the principles behind the small scaphes >>> on many dials. (Here's a Wikicommons photo of a Leonhard Miller dial). >>> The Greek and Roman scaphes, like the one in Dan-George's photo, were >>> hollow sections of either spheres or cones, with a gnomon at their centre. >>> Their mode of operation seems quite straight-forward. >>> But the scaphes in diptyches weren't like that. They appear to be tiny >>> slices of much larger spheres. And the gnomons are, of course, far from the >>> centre. The 'furniture' on several of them seems similar to stereographic >>> projections. But, since instrument-makers then were well able to make >>> astrolabes with stereographs, perhaps not. >>> So: can someone point me to an article which discusses these small >>> scaphes? Or, in the meantime, help me understand how and why they were >>> used? Why don't we make them any more? Or: are there any contemporary >>> examples, using, say, bowls, or bird-baths or skateboard parks? >>> best wishes, >>> >>> Peter >>> >>> ----------- >>> Peter Mayer >>> Department of Politics & International Relations (POLIR) >>> School of Social Scienceshttp://www.arts.adelaide.edu.au/polis/ >>> The University of Adelaide, AUSTRALIA 5005 >>> Ph : +61 8 8313 5609 >>> Fax : +61 8 8313 3443 >>> e-mail: [email protected] >>> CRICOS Provider Number 00123M >>> ----------------------------------------------------------- >>> >>> This email message is intended only for the addressee(s) >>> and contains information that may be confidential >>> and/or copyright. If you are not the intended recipient >>> please notify the sender by reply email >>> and immediately delete this email. >>> Use, disclosure or reproduction of this email by anyone >>> other than the intended recipient(s) is strictly prohibited. >>> No representation is made that this email or any attachment >>> are free of viruses. Virus scanning is recommended and is the >>> responsibility of the recipient. >>> -- >>> >>> --------------------------------------------------- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>>
--------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
