Sundials described here are those I could photograph myself. Others are visible to the public but some are in private places or in museums (Musée du Louvre, Musée de la Marine, Conservatoire des Arts et Métiers).
Learn more about sundials in Paris, with the following book:
"Cadrans Solaires de Paris" de Andrée Gotteland et Georges Camus, CNRS Editions. ISBN 2-271-05533-4