A brave attempt - there seem to be as many classification systems for
dials as there are diallists. ....
I believe that the professionals writing museum catalogues have their own
classification system but I've not found out where it's written up -
anyone know?
I can't respond very fully to this at this time, as I'm at a meeting of the
Scientific Instrument Commission in Stockholm this week. However, this
topic has been discussed on this list before, and I would say that there
are standards for dial classification, and these are published in works by
myself and my colleagues. More on this later. For now:
1. The type of "hours" that the dial is intended to indicate is
significant eg equal, temporary, Babylonian, Italian etc.
yes
2. The dial plate may be movable, as in most of the card-dials etc.
By movable, I assume you mean portable as opposed to fixed dials.
BTW, I note that you classify the shephers' (or cylinder) dial as having
a movable gnomon, whereas I would say the gnomon is fixed - it always
points south - whilst the dial plate rotates with the date behind it.
This is mistaken. In a pillar dial, once the gnomon is set to the date,
the instrument is turned until the gnomon points in the direction of the
sun's azimuth at that moment. It is only due south at solar
noon. Otherwise the gnomon is easterly or westerly.
At 06:56 PM 10/15/01 +0100, Chris Lusby Taylor wrote:
By the way, John, could you please note in the BSS Glossary that the
correct term for a diagonal scale (used to interpolate the shadow edge
between successive hour lines) is a nonius, from Pedro Nuñez, the
Portuguese inventor.
I do not think that this is right. I think you are referring to a
transversal rather than a nonius.
Happy dialling,
Sara
Dr. Sara Schechner
David P. Wheatland Curator
Collection of Historical Scientific Instruments
Harvard University, Science Center B-6
Cambridge, MA 02138
Tel: 617-496-9542
Fax: 617-496-5932
