Petrus Apianus Draws Up a Calendar

The dullest page in Petrus Apianus's magnificently illustrated Astronomicum Caesareum is folio K I verso (Figure 1). Under the title "Comparison of the Greek and Latin months" appears a partial calendar in two columns. The column on the left begins with 26 July and includes the rest of July, August, September and 1 October, in the form assigned them by the Julian ecclesiastical calendar, the standard calendar of the medieval and Renaissance west until the Gregorian Calendar reform of the calendar decreed in February 1582. The column on the right begins with the first day of Hecatombaion, the first month of the calendar of ancient Athens. It continues through Metageitnion, the second month, and the beginning of Boedromion, the third. Apianus treats these months, oddly, as if they too were Roman, as a comparison with the left-hand column shows. He makes the first day of each Athenian month the Kalends. Then he counts down to the Ides, which he sets on the fifth day; to the Nones, which he sets on the 13th of Hecatombaion and the 15th of Metageitnion; and finally, after the Nones, to the Kalends of the next month. Though Apianus supplies no detailed explanation, he does offer supplementary materials on the right: a list of the Athenian months in order, a list of the Athenian names for the days of the lunar month (which was divided quite differently from the Roman month, into three sections of almost equal length), and a couple of historical references to Nicias - the leader of the Athenian expedition to Syracuse during the Peloponnesian War, whose defeat in 413 B.c. Thucydides narrates in the magnificent, climactic books of his History}Both subject matter and presentation seem dry enough to eliminate the need for caucus races: dry enough, indeed, to induce slumber in the normal reader. The table contrasts sharply with many of the splendid and original visual effects achieved by Apianus elsewhere in his book. The Astronomicum, after all, included gorgeous diagrams of planetary models, splendid images of eclipses, and ingenious efforts to record the changing appearance of Halley's comet and four others, day by day. The comet images gave Apianus's work lasting value as a source of data for astronomers - including Halley - long after Kepler denounced it as a fanciful rechauffe of Ptolemy.2Apianus, after all, was not only a humanist, an antiquary, and a printer of astronomical textbooks and tables, but also a man with a keen visual sensibility. A skilled observer of the heavens, he instructed readers on how to look safely at eclipses through two thick pieces of glass of different colours, with a thin sheet of paper glued between then and perforated at one point, and accurately noted that comets' tails are normally directed away from the Sun. No wonder, then, that his book seemed a marvel of design even in the decade that saw the appearance of Fuchs's Herbal and Vesalius's Fabrica? In the brilliant company of Apianus's volvelles and eclipse diagrams, carefully coloured in his shop before the book was distributed to buyers, the calendar table seems a verbal wallflower. Apianus himself, however, saw it as a particularly instructive visual tool: "With the aid of this journal", he told readers, "your own eyes can teach you everything about the months and the beginning of the Attic year, more clearly than light itself".4 What then did the Comparison teach, and how, and why did Apianus think it mattered? And what does it tell us about the uses of illustrations in astronomical and other literature of this period?The Roman part of the diagram - the left-hand column - is a standard, if rather partial, treatment of the Julian ecclesiastical calendar, as that took shape in the fifth and sixth centuries and continued to develop, in its sacred components, over time. Apianus lays out the data in parallel columns. They include: the names of the months, a repetitive series of letters from A to G, and the Roman dates for the days in question. …