The Calendar and the Inscription Beneath It
The calendars encircling Leardo’s three maps constitute exceptional additions. Of these calendars, the one on the Society’s map is the most interesting. The inscription in the panel below the circles, in part an explanation of the calendar, is somewhat awkwardly phrased in the Venetian dialect of the fifteenth century, but, although it lacks the beginning of each line, the meaning is fairly clear, especially when certain of the missing lines are reconstructed from the corresponding inscription on the map in Vicenza.[6]
In the first two lines the cartographer makes an excursion into the realm of theology. According to Dr. Arthur C. McGiffert, to whom the present writer submitted the passage, this part of the inscription is “evidently not the work of a theologian, for it makes God the creator ‘of all things created and uncreated’ (the credal phrase is ‘things visible and invisible’), and in the next clause runs the Trinity (‘three persons and one common substance’) and the person of Christ together as if they were the same thing. There are reminiscences of the Nicene creed, but the whole is theologically a hodge-podge.”
This passage is followed by a statement that the map shows how the land and islands stand in relation to the seas and how the many provinces and mountains and principal rivers are distributed on the land. Then, on the asserted authority of Macrobius, “a very excellent astrologer and geometrician,” figures are given for the dimensions of the earth and of various heavenly bodies. These are quite fanciful, bearing little relation to the corresponding figures actually cited by Macrobius.[7]
The astronomical details are followed in the third paragraph by the explanation of the calendar. The latter consists of eight concentric circles, of which the innermost gives the dates of Easter for ninety-five years, from April 1, 1453, to April 10, 1547; when Easter falls in April, A is written in the small compartment, when in March, M; leap years are designated by B (“bissextile years”).
The second circle shows the names of the months, beginning with March, which was officially reckoned the first month of the year in the Republic of Venice until as late as 1797[8]; it also tells the day, hour, and minute when the sun enters each of the twelve signs of the zodiac.
The third, fourth, fifth, and sixth circles enable one to calculate the phases of the moon. In the third circle the first nineteen letters of the alphabet represent in order the years of the Metonic lunisolar cycle. These years were usually designated by the golden numbers, but before the Gregorian reform letters were frequently employed in place of the numbers. Leardo explains that C stands for 1453, D for 1454, and so on until T is reached, after which we begin over again at A.[9] A letter is placed opposite the figures (in the fourth, fifth, and sixth circles) showing respectively the day of the month, the hour of the day, and the “point of the hour” at which the “conjunction of the moon” (i. e. new moon) will take place in the years to which the letter refers. For example, there will be a new moon on April 8, 1453, at 16 hours, 200 points.[10] Leardo adds that there are 1080 points in an hour.[11]
The seventh circle gives the dominical, or “Sunday,” letters; these are indicated opposite the days of the month (fourth circle) on which Sunday falls in the years designated by the seven first letters of the alphabet. If we know the dominical letter for any particular year, we may thus determine the days of the week.[12] Leardo, however, does not specify the years to which the dominical letters in his calendar refer.
The eighth and ninth circles give the lengths of the days in hours and minutes.[13] From this we see that the vernal equinox fell on March 11, inasmuch as the calendar was constructed before the Gregorian reform. Finally, in the tenth circle saints’ days and other religious festivals are shown.[14]
The four figures in the spaces between the calendar and the outer edge of the parchment represent the four evangelists: the lion for St. Mark, the bull for St. Luke, the angel for St. Matthew, and the eagle (of which only the head shows) for St. John.[15]