the depiction of a spherical heavenly vault separating the Earth from an outer realm is similar to the first illustration in Sebastian Münster's Cosmographia of 1544, a book which Flammarion, an ardent bibliophile and book collector, might have owned. Context in Flammarion's book In Flammarion's L'atmosphère: météorologie populaire, the image refers to the text on the facing page (p. 162), which also clarifies the author's intent in using it as an illustration: The same paragraph had already appeared, without the accompanying engraving, in an earlier edition of the text published under the title of L'atmosphère: description des grands phénomènes de la Nature ("The Atmosphere: Description of the Great Phenomena of Nature," 1872). The correspondence between the text and the illustration is so close that one would appear to be based on the other. Had Flammarion known of the engraving in 1872, it seems unlikely that he would have left it out of that year's edition, which was already heavily illustrated. The more probable conclusion therefore is that Flammarion commissioned the engraving specifically to illustrate this particular text, though this has not been ascertained conclusively. Literary sources The idea of the contact of a solid sky with the Earth is one that repeatedly appears in Flammarion's earlier works. In his Les mondes imaginaires et les mondes réels ("Imaginary Worlds and Real Worlds", 1864), he cites a legend of a Christian saint, Macarius the Roman, which he dates to the 6th century. This legend includes the story of three monks (Theophilus, Sergius, and Hyginus) who "wished to discover the point where the sky and the earth touch" (in Latin: ubi cœlum terræ se conjungit). After recounting the legend he remarks that "the preceding monks hoped to go to heaven without leaving the earth, to find 'the place where the sky and the earth touch,' and open the mysterious gateway which separates this world from the other. Such is the cosmographical notion of the universe; it is always the terrestrial valley crowned by the canopy of the heavens." In the legend of St. Macarius, the monks do not in fact find the place where Earth and sky touch. In Les mondes imaginaires Flammarion recounts another story: Flammarion also mentioned the same story, in nearly the same words, in his Histoire du Ciel ("History of the Sky"): The Letters referred to are a series of short essays by François de La Mothe Le Vayer.