Sara, et al,
Of all the Porter dials I've seen the CalTech dial (cylindrical equatorial - I
suppose best describes it) comes closest to matching that modeled image
provided by Aleks. However, as you note the stylus of the CalTech dial is not
projecting radially from the plate surface, like that
Nicola,
Great explanation of terminology. I completely agree and applaud your use of
the historical literature for guidance.
All best,
Sara
Sara J. Schechner, Ph.D.
David P. Wheatland Curator of the Collection of Historical Scientific
Instruments
Department of the History of Science, Harvar
