Decipherment of Rongorongo - Barthel

Barthel

German ethnologist Thomas Barthel, who first published the rongorongo corpus, identified three lines on the recto (side a) of tablet C, also known as Mamari, as a lunar calendar. Guy proposed that it was more precisely an astronomical rule for whether one or two intercalary nights should be inserted into the 28-night Rapanui month to keep it in sync with the phases of the moon, and if one night, whether this should come before or after the full moon. Berthin and Berthin propose that it is the text which follows the identified calendar which shows where the intercalary nights should appear. The Mamari calendar is the only example of rongorongo whose function is currently accepted as being understood, though it cannot actually be read.

In Guy's interpretation, the core of the calendar is a series of 29 left-side crescents ("☾", colored red on the photo of the table at right) on either side of the full moon, a pictogram of te nuahine kā ‘umu ‘a rangi kotekote 'the old woman lighting an earth oven in the kotekote sky'—the Man in the Moon of Oceanic mythology. These correspond to the 28 basic and two intercalary nights of the old Rapa Nui lunar calendar.

Heralding sequences: Two instances of the "heralding sequence" from line Ca7, one from before and one from after the full moon. The fish at the end of the latter is inverted, and (in the sequence immediately following the full moon only) the long-necked bird is reversed.

These thirty nights, starting with the new moon, are divided into eight groups by a "heralding sequence" of four glyphs (above, and colored purple on the tablet at right) which ends in the pictogram of a fish on a line (yellow). The heralding sequences each contain two right-side lunar crescents ("☽"). In all four heralding sequences preceding the full moon the fish is head up; in all four following it the fish is head down, suggesting the waxing and waning of the moon. The way the crescents are grouped together reflects the patterns of names in the old calendar. The two ☾ crescents at the end of the calendar, introduced with an expanded heralding sequence, represent the two intercalary nights held in reserve. The eleventh crescent, with the bulge, is where one of those nights is found in Thomson's and Métraux's records.

Guy notes that the further the Moon is from the Earth in its eccentric orbit, the slower it moves, and the more likely the need to resort to an intercalary night to keep the calendar in sync with its phases. He hypothesizes that the "heralding sequences" are instructions to observe the apparent diameter of the Moon, and that the half-size superscripted crescents (orange) preceding the sixth night before and sixth night after the full moon represent the small apparent diameter at apogee which triggers intercalation. (The first small crescent corresponds to the position of hotu in Thomson and Métraux.)

Seven of the calendrical crescents (red) are accompanied by other glyphs (green). Guy suggests syllabic readings for some of these, based on possible rebuses and correspondences with the names of the nights in the old calendar. The two sequences of six and five nights without such accompanying glyphs (beginning of line 7, and transition of lines 7–8) correspond to the two groups of six and five numbered kokore nights, which do not have individual names.