I'm not convinced that it isn't an arc. When I was started looking into the question I first took a compass and drew a series of circles all intersecting at one point. Then I took a pencil and marked what I judged to be the lowest point of each circle. I quickly saw that I was marking another circle of the same diameter as the others. Even if I judged wrong it would have to result in a closed figure rather than an open one like a hyperbola.
I put the center one radius below the 12 noon point where the curves meet and the resulting arc intersects the arcs of the 'hat' as it should, at least at the resolution of my printer. It reminds me of the time I trisected an angle. I was even surer of myself then than I am now and I bet you can guess how that turned out. :) John On Sat, 20 Mar 1999, fer j. de vries wrote: > Wm. S. Maddux wrote: > > > > Re the hour limitation line/curve for a Capuchin dial, > > John Hoy wrote: > > > > > Is that line an arc of a circle? > > > > Fer de Vries wrote: > > > > >The line through the endpoints of the date arcs > > >isn't an arc of a circle. > > >I calculate or construct a number of endpoints and > > >connect them to a smooth line. > > > > I believe that the curve segment in question is a > > portion of an hyperbola. > > > > W. Maddux > > Hello Bill, > > I had in mind this curve is a part of an hyperbola but I was not for > sure. > Now I looked up in the special bulletin about the Eisinga carddial and > indeed there is stated this curve is a part of an hyperbola. > I myself never proofed it. > Thank fot noting it. > > Best wishes, Fer. > > -- > Fer J. de Vries > [EMAIL PROTECTED] > http://www.iaehv.nl/users/ferdv/ > lat. 51:30 N long. 5:30 E > >
