Re: Earliest Sundials

[Gianni Ferrari]

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' E Mailto : [EMAIL PROTECTED]