Die Konstruktion von Kreisen und die Entdeckung zweier wuchtiger Türme auf dem Klosterplan von St. Gallen.

This paper focuses exclusively on circular figures on the Plan of St. Gall. Made of parchment, the Plan was produced in the scriptorium of the Abbey of Reichenau/Lake Constance in the early 9111 century and dedicated, following the literary conventions of the time, to Abbot Gozbert (816-837) of the neighbouring Abbey of St. Gallen. The document shows a schematic plan for a complete monastery with all sorts of buildings and fenced-off areas to meet the needs and requirements of a large monastic community at the time. Among those numerous buildings rendered on the Plan, one finds some circular structures like St. Michael's and St. Gabriel's Towers at the front of the Abbey Church, and also a henhouse and a goosehouse in the right upper corner of the parchment. The round structures and concentric circles forming these buildings are freehand drawings in pen and red ink that are not compass-drawn. Most scholars have assumed so far that circular structures on the Plan would have been drawn with the help of compasses used for scratching «blind lines» onto the surface of the parchment. However, close technical analysis reveals the procedure applied only to predefine the planning of round and circular structures. The draughtsmen used dividing compasses beforehand only to prick tiny and hardly visible punctures («prickings») into the parchment at arbitrarily chosen spots along the intended circumference of circular buildings, and then they drew the final design by pen and red ink freehand. Inconspicuous pricking of parchment in order to predefine geometrical figures seems to have been a technique widely applied by monastic scriptoria all over early medieval Europe. Early medieval scribes would apply this technique not only for predefining geometrical figures, drawings and illuminations but also for creating the lining and type area on text pages, for the lay-out of manuscripts in general. The findings presented in this paper are the results of my analysis of digital images of the Plan of St. Gall as the original document is not available to physical examination. [ABSTRACT FROM AUTHOR]