"Ancient Egyptian Astronomy: timekeeping and cosmography in the New Kingdom"- 1999 by Sarah Symons is a remarkable doctoral thesis.
In contributions on the history of sundials the L-shaped sundial from Egypt dating from 1500 BC. is mentioned as the earliest known sundial. Usually the operation of the sundial is described as follows: When the long stem with 5 variably spaced marks was oriented east and west in the morning, an elevated crossbar on the east end cast a moving shadow over the marks. At noon, the device was turned in the opposite direction to measure the afternoon "hours." The elevation of the cross bar varies with the season. Time measurement is done in seasonal hours. This description is based on a theory of the German Egyptologist Borchart in 1920 and the Dutch mathematician Bruins in 1965. Sarah Symons rejects in her doctoral thesis this theory and description. - the device was not oriented east and west but pointed to the sun - there was no cross bar added to the device and there was no variable elevation - time measurement was not done in seasonal hours. The simple ratios between the markings on the scale suggest a convenient 'rule' for making a clock. Her detailed arguments are based on both the mathematics of gnomonics and thorough knowledge of Egyptology and textual sources.. If she is right, and it looks, we need to rewrite the history of the sundial. Thank you Gianni to draw our attention to this publication. Willy Leenders Hasselt in Flanders (Belgium) Visit my website about the sundials in the province of Limburg (Flanders) with a section 'worth knowing about sundials' (mostly in Dutch): http://www.wijzerweb.be Op 13-nov-2010, om 20:40 heeft Gianni Ferrari het volgende geschreven: > In the website > https://lra.le.ac.uk/handle/2381/8546 > there is the doctoral thesis by Sarah Symons entitled > "Ancient Egyptian Astronomy: timekeeping and cosmography in the New Kingdom"- > 1999, pages. 230 > It is very complete! > > In the thesis also the old Egyptians sundials and the seasonal hours are > discussed, with tables, graphs, formulas, etc. (page 128-151) > > Regards > Gianni Ferrari > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial >
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