Dear Frank, Frank King wrote:
> You don't need a polar-oriented gnomon to > indicate equal hours (starting at noon or > midnight) although it certainly helps. > The way I view the transition from temporary to equal hours follows Zinner's reasoning. The usual medieval sundial was vertical and semi-circular, with 12 (equally spaced) temporal hour lines. A perpendicular gnomon was inserted into the center, where all lines intersect. How to adapt this lay-out to the equal hours of clocks? Zinner imagines that people have been experimenting with bending the gnomon and/or slightly rotating the hour lines to or away from the meridian, until success. One could have attained the same result by moving the gnomon down (until its tip would fall on the imaginary pole-style arising from the center), but that would have required a more difficult mental step. Of course this reasoning applies only to 'anchored' equal hours, which start from a fixed time point in the day, such as noon or midnight. I would not dare to speculate on how sundials for Italian (or Babylonian) hours evolved. When did such dials emerge? Do you know, Gianni? Best regards, Frans Maes --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
