Gecko Dial Installed!
Hello All: After nearly two years of work, my large stained glass sundial (The Gecko Dial) is finally installed in the bay window that we made especially for it at my home in Tucson. It is only the 2ond permanently installed stained glass sundial in the United States. (The other one is in a private home in Tennessee). With help from my stained glass teacher and her husband at Ocho Stained Glass, we installed it on New Years Day. To avoid cracking during installation, we moved it on a piece of rigid particle board to prevent flexing. The gnomon is still under construction, but tests with the gnomon prototype showed that it keeps the correct time and date. You can read all about it and see photos of the installation and the installed dial at www.stainedglasssundials.com or you can go directly to these photo links to see just the photos: Photo of Glass Painting: http://advanceassociates.com/Sundials/Stained_Glass/sundials_files/Stained_Glass_Sundial_79_glass%20painting_b.jpg Photo of completed Center Panel: http://advanceassociates.com/Sundials/Stained_Glass/sundials_files/Stained_Glass_Sundial_79_finished_panel.jpg Photo of Installation: http://advanceassociates.com/Sundials/Stained_Glass/sundials_files/Stained_Glass_Sundial_79_installation3.jpg Photo of Installed Dial (interior): http://advanceassociates.com/Sundials/Stained_Glass/sundials_files/Stained_Glass_Sundial_79_finished_interior2.jpg Photo of Photo of Installed Dial with Side Panels: http://advanceassociates.com/Sundials/Stained_Glass/sundials_files/Stained_Glass_Sundial_79_finished_interior1.jpg Hope you like it! If any of you are visiting Tucson, you are most welcome to come see it. John John L. CarmichaelSundial Sculptures925 E. Foothills Dr.Tucson AZ 85718-4716USATel: 520-6961709Email: [EMAIL PROTECTED] Websites:Sundial Sculptures: http://www.sundialsculptures.comStained Glass Sundials: http://www.stainedglasssundials.com
Gnomon location holes
A couple of months ago, Mike Cowham asked the SML for an explanation of the two small dots or holes seen on the dialplates of antique horizontal dials, just where the tip of the gnomon meets the dialplate. Several suggestions were made, such as their use as alignment marks to position the gnomon. Tony Moss made the suggestion that they acted as location points for a swivelling straight-edge which was used to mark out the hourlines. I have recently come across a picture of a c.1700 declinatory by John Coggs which gives support to Tonys suggestion. This small instrument consists of a circular horizontal dial which is free to rotate on a larger square plate with a protractor scale. As befits a portable instrument, the gnomon has the facility of folding flat. The resulting hinge mechanism means that the southern tip of the gnomon is truncated and it thus stops just short of the VI-VI line. BUT, the two holes are clearly visible at the origins of delineation. Since the holes cannot, in this case, be used to position the gnomon correctly, it seems highly likely that they were part of t! he delineation process. When were these holes first used? Very early (before 1600) horizontal dials usually had very thin gnomons and no evidence of the holes. Elias Allens double horizontal dials in the 1620-1650 period do have them. Can anyone give other examples of early dials with these delineation origins. Regards, John DavisDr J R DavisFlowton DialsN52d 08m: E1d 05m
Re: Earliest Sundials
Among the sundials of the ancient Islam - made before 1500 - the only one with a polar style is that, already mentioned by Fer de Vries, drawn by Ibn al Shatir in 1372 and placed at the base of the minaret of the great Umayade mosque in Damascus. The existing sundial, with a beautiful polar style, is a reconstruction made in XIX century of the original one, of which some fragments remain in the National Archaeological Museum of Damascus. The use of the equal hours in the sundials - however always with a style perpendicular to the plane - seems to have been introduced by Aboul Ali Hhassan al Marrakushi around 1280. In his book on the Arab sundials, written in 1282 , translated by J.J. Sedillot and published in Paris in 1839 with the title "Traite des instruments astronomique des arabes", the chapters XIV and following of the Book III are devoted to the "construction [of the lines] of the equal hours" on sundials drawn on different planes (horizontal, vertical, declining, inclining ). The Chapter XIV begins with the sentence "This [matter] is part of the things that we write in this work as a result of our meditations and reflections." In a footnote Sedillot affirms that "This passage let us know that before Aboul Hhassan no one had thought to draw the [lines of the] equal hours [on the sundials] ". In the text that follows this sentence Aboul Hhassan explains also that all the hour lines pass through the same point, "the projection of the North Pole on the plane", but in any part of the work he mentions the possibility to use a polar style. My best wishes for a peaceful New Year Gianni Ferrari 44° 39' N 10° 55' EMailto : [EMAIL PROTECTED]
