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

Seven folding engraved plates. 2 p.l., xxxx, 738 pp., 1 leaf of errata; 2 p.l., lvi, 680 pp. Two vols. Large 4to, attractive cont. marbled sheep, flat spines richly gilt, green morocco lettering pieces on spines. Paris: la Veuve Valade, 1786-89.

First edition and quite scarce on the market. “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.). Revised and coordinated, these memoirs were reprinted in the two-volume Traité analytique des mouvements apparents... More