Jim Lattis wrote: > > Forgive me for issuing this query in place of doing > my own research, but time presses.... > > An artist friend wants to make a sundial of a particular design, > which he describes as a "globe sundial designed by Thomas Jefferson". > the rough sketch he sent me suggests that the dial face is > carved on a spherical surface. he has no information about > the gnomon. is this some kind of variation on a hemispherium? > > if anyone recognizes this design and can direct me to a source > i may be able to make sure he doesn't waste time cutting > stone before we have a clear idea of the concept. > > thanks very much. -jim lattis > > -- > Jim Lattis [EMAIL PROTECTED] "What's so amazing that > Director, UW Space Place voice: 608-263-0360 keeps us stargazing, and > U. of Wisconsin-Madison fax: 608-263-0361 what do we think we might > http://www.sal.wisc.edu/~lattis see?" -Kermit t. Frog
Dear Jim, A picture of a sundial on a sphere is on one of my internet pages under number 9. http://www.iaehv.nl/users/ferdv/fotos.htm This is the most common type of such a dial. The lines are like longitude lines on a globe. But on a sphere also a style, parallel to the earth's axis, can be placed. It is just about a year ago that in our country an old spherical dial of this type was discovered. In the Dutch book by Johann Hermann Knoop, 1761, this type of dial is described. I have scanned an example of such a dial out of this book and attached as sphere.jpg to this message. A method to construct the lines onto such a body is to project a dia with 15 degrees spaced lines in the direction of the ploe style. You see there are more possibillities to make a spherical dial and I would be pleased to know what type is wanted. Fer.
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