At 15.19 21/06/97 +0300, you wrote:
>I am interested in the above mentioned types of sundial.
>1.Where was the gnomon placed un relation to the hour marked stone?
>2.Was there any indication as to the lattitude in that type of sundial.
>3. What is the difference between the hemispherical and the conical type?
>4. What kind of scientific knowledge did a maker have to possess in order
>to make such a dial?
>5. What kind of knowledge did the user have to possess?
>
>
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Ronit,
easy to respond to your questions.
1. The gnomon was orizontal placed in the origin of the hour lines, at the
top of the curve (not easy to esplane without a drawing, indeed), not the
same in the hemisphaerium that it was an emispherical vase opened to the
zenit. In this last case the gnomon was standing right up pointing to the
zenit, but some medieval drawing and fisical example like that in the
Science Museum of Florence have the gnomon parallel to the eart axe. The
vertical inclined hemisphere use a hole in its top as gnomon.
2) No, the only way to measure the latitude for what the dial was made, is
to measure the angle of the inclination of the dial.
3) It depend on the meaning of the words, for me hemispherical means
hemispherical, that is a half of a sphere. In this case we have three tipe
of hemispherical roman dials: orizontal (I wrote before), vertical and
vertical inclined (I wrote before). Probably you mean the hemicyclium that,
following the meaning of the word it was a sundial done inside a, more or
less, a quarter of sphere. The hour lines are arcs of circle. On the other
hand the conical sundial is very similar to the hemiciclic one but the
section is conical and the lines are right.
4) My experience say that those sundials was made in a great number by
artisans with an average scientific knowledge. Many of the instruments are
not so precise as they want to be, but good enough for common people.
Anyway, almost the leader of the workers, must know the "analemma".
5) Normal knowledge to read it, and to do it, it's very easy.
Short anwers mine. If something is not clear let me know.
Anyway you can look at the book of Mrs. Gibbs, "Greek and Roman Sundials",
or at the great bibliography that you can easily find. If you need help,
please write me.
Regards
Mario Arnaldi
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MARIO ARNALDI
Viale Leonardo, 82
48020 Lido Adriano RAVENNA
ITALY
E-Mail - [EMAIL PROTECTED]
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