Essai sur les Phénomènes relatifs aux disparitions périodiques de l'Anneau de Saturne.
One folding engraved plate. 2 p.l., xxxii, 444 pp. 8vo, attractive antique calf-backed marbled boards, flat spine gilt. Paris: Valade, 1776.
First edition of this uncommon book on the varying appearance of the rings of Saturn. “From 1764 to 1783 he [Dionis] wrote a series of important memoirs on the application of the most recent analytic methods to the study of the principal astronomical phenomena (eclipses, occultations, reductions of observations, determination of planetary orbits, etc.)…All these works are dominated by an obvious concern for rigor and by a great familiarity with analytical methods…their reexamination in the light of present possibilities of calculation... More