The solar instruments built into and on the church of Santa Maria Novella in Florence were *not* constructed by Alberti but by Egnatio Danti. These include:
(1) an armillary sphere on the facade--built in 1574 for determining the time of the vernal equinox by the sun's shadow.
(2) an astronomical quadrant on the facade--also built in 1574 for observing the equinoxes and solstices, to determine the length of the year, and check the value of the obliquity of the ecliptic.
(3) the "meridiana"--i.e., the gnomon (a hole in the circular window 21.3 m high) and meridian line drawn on the pavement inside the church, upon which the solar image fell. It was built soon after the first and second instruments, but not completed. His intention was to count the days between the reappearances of the sun at the same equinox in order to determine the length of the tropical year.
By loose definition, any of these could be called a "sundial," but I assume you are referring to the gnomon and meridian. Without knowing the placement of the numerals you mention, I cannot interpret them for you (I don't have a picture of the meridian in front of me). For more information on this and similar meridians, you might enjoy looking at John Heilbron's book, _The Sun in the Church_.
Best wishes, Sara Schechner Sara Schechner, Ph.D. David P. Wheatland Curator Collection of Historical Scientific Instruments Department of the History of Science Harvard University, Science Center 251c Cambridge, MA 02138 Tel: 617-496-9542 Fax: 617-496-5932 -
