Hello Claude & others,
From: [EMAIL PROTECTED] Date sent: Sat, 28 Oct 2000 17:42:29 -0000 To: [email protected] Subject: Soler's Bifilar Sundials <color><param>7F00,0000,0000</param>> > I have searched the web for additional information on Mr. Soler's > > motivation. I found a large pole-style bifilar dial, including > >picture, in Barcelona, where the catenary is a parabola, > (snip) <underline><color><param>0000,8000,0000</param>http://www.ub.es/geohum/inventari/fitxes/invt106.htm</underline></color> <color><param>7F00,0000,0000</param> > > As one can see in the photo, the N-S gnomon is horizontal. The E-W > gnomon is a parabola opening upwards. The resulting hour lines are > not straight except near noon. This dial was built in 1993 for the > Olympic Village of Barcelona. </color>You are right; the N-S gnomon is NOT a pole-style. That brings me to some additional input to the terminology issue here, following up on what Fer de Vries wrote: <color><param>7F00,0000,0000</param>> This remark has more to do with 'classification of sundials' and > that's a different but also interesting discussion. To my opinion > this dial surely is a bifilar dial. > You are right by stating 'the second shadow is not needed to tell > time', but a sundial is able to show us many more phenomenae > of the sun then just the dayly time. It also may show the date or > the sun's altitude or other phenomenae and still it is a sundial. To > read the date in this example we need the second shadow too. > And for that part this dial is a bifilar dial, however in stead of > filars 2 edges of planes are used, but the principle is the same. </color>I agree partly. Having followed the discussion on this issue on the list, I arrived at the following view: One should compare the various bifilar dials with the case of the nodal dial and the combined pole-style/nodal dial. With a nodal dial, the shadow of one point (or node) simultaneously indicates time and date. This may be the tip of an obelisk or a pin, etc. This compares with the original bifilar dial by Michnik, where one point (the intersection of two shadow lines) simultaneously indicates time and date. The dial in the picture from Barcelona is another example. When a node is located on a pole style, the pole-style indicates the time, and the node additionally indicates the date. This is what I call a combined pole-style/nodal dial. An example is the horizontal dial (nr. 2) in Genk. Likewise, in the bifilar dial in Genk the pole style indicates the time, and the point where the two shadows intersect additionally indicates the date. I would call this a combined pole-style/bifilar dial; in this case a combined horizontal/bifilar dial. The dial in Appingedam then is a combined polar/bifilar dial. <color><param>7F00,0000,0000</param>> In the Genk park dial there may have been the > desire to combine a natural curve, the catenary that a hanging chain > forms, and a polar style. > His drawings showed a proposed size that would have the > chain hanging from supports 3.5 m high and 5 m apart. Unfortunately, only > a small version was built and the chain is easily vandalized. </color>The drawing in the hand-out at the international symposium that marked the official start of the Genk Sundial Park project (June 20, 1998) shows exactly the size that has been realized. I would have loved to see the dial in the size you mention! <color><param>7F00,0000,0000</param>> Claude Hartman > 35N 120W </color>Regards, Frans <nofill> ===================================== Frans W. Maes Peize, The Netherlands 53.1 N, 6.5 E www.biol.rug.nl/maes/ =====================================
