 "Syzygies and Lunar Quadratures" (syzygy and quadrature are terms in astronomy) consists of two parts—the first is an account of a lunar voyage by a Frenchman, Onésimo Dutalon in epistolary form, and it precedes another letter containing an astronomical almanac.Both are addressed to a Don Ambrosio de Echevarria (an "observer of lunar movements") and are written by "anctitones", the inhabitants of the Moon.In their first letter, the anctitones write to Echevarria about a visit they received from Onésimo Dutalon, a French astronomer, who had written them a very informative and erudite letter with data about syzygies and quadrature.