Hello Edley, Indeed, I am F.J. and no relative to T.J. de Vries.
T.J. is some 8 years younger than I am and he was in 1978 one of the founders of De Zonnewijzerkring in the Netherlands. At that time he was very interested in gnomonics and he developed some new types of sundials of which the most important is the bifilar sundial with one curved filar. He had an interesting correspondence with Fred Sawyer of NASS about a number of new concepts in gnomonics such as the equant sundial, developed by Fred Sawyer. T.J. de Vries then made his variant with parallel and equidistant hourlines. Also the polar dial with the cycloid shaped gnomon as published in our bulletin is an idea of T.J. de Vries, not mine as you wrote. He still is a member of our Sundial Society, however not active and his interests have changed into other things. I have no idea about your thoughts in relation to a "Cardioid curve". I am not familiar with such mathematics and I don't dare to say anything about it. Best wishes, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: "Edley" <[EMAIL PROTECTED]> To: "fer j. de vries" <[EMAIL PROTECTED]> Cc: "Sundial, Mailinglist" <[email protected]> Sent: Saturday, November 24, 2001 7:50 AM Subject: NASS References. > Hello Fer, > > Excuse me for my ignorance. > Being a new member of NASS, going through the references in the > Repository CD, I see references to a T. J. de Vries and to a F. J. de > Vries. I take it that you are the F. J., who is the T. J. ? > > I am very interested in sundials with uniform indications of time > movement and was attracted to your Cycloid Polar design as well as > the comment in Fred Sawyer's Equant article from T. J. de Vries on > mapping the horizontal dial gnomon shadow crossings of a curve into > uniformly spaced parallel lines. I've tried mapping the curvature of > a gnomon to map the shadow of a vertical south dial into uniform > parallel lines such as your cycloid unit at specific dates. The > curves for several times of the year are so different that I've not > yet been able to envision what a solid would look like for the whole > year ( If there is one ).(For Local Mean Time) > > btw: Doesn't the equant curve shape remind you of a "Cardioid curve"? > (The Cardioid being related to the cycloid by the moving circle > being on a circle of equal size rather than a straight line.) > > Your software and other articles have also been very helpful and > informative. I wish to thank you for your thoughts, information and > the obvious time you have given. > > Thanks! > > Edley McKnight > > [43.126N 123.526W] >
