The Plan of St. Gall :: :: University of Virginia Library

Reproduced in figure 7 is a portion of the building site
to the north of the Church, showing (from top to bottom)
the western end of the Outer School, the House for Distinguished
Guests, and the Kitchen, Bake, and Brew
House for Distinguished Guests. Examination of the open
spaces between these structures shows that the parchment
here has never been touched by a stylus. This had noticeable
consequences for the style of these drawings: the walls
that form the outer boundaries of these houses do not stay
"in line," most drastically so in the case of the Kitchen,
Bake, and Brew House, whose southern gable wall slants
away from its proper alignment by an angle of two degrees.
If the parchment surface had been provided with guiding
construction lines, the draftsman's hand could never have
slipped away from its regular course as far as it did when
drawing the southern walls of the Kitchen and Bake House,
converting a building that was of rectangular shape into a
trapezoid structure.

An even more flagrant case of the divergence of lines
meant to run parallel to one another is to be found on the
opposite side of the Plan in the alignment of the three
buildings that contain the Mill, the Mortar, and the Drying
Kiln (fig. 8). This kind of linear aberration might easily
occur in the process of copying when the translucency of
the skin on which the Plan was being traced was temporarily
marred by changing light conditions, but would be unlikely
to occur on an original where the quill of the draftsman
followed the grooves of a constructional underdrawing.

On the Plan of St. Gall such grooves can be discovered
neither on the recto in the form of the familiar furrows nor
on the verso in the form of thin ridges. Throughout the
entire expanse of the Plan, with its total of forty separate
structures of varying size, no trace is to be discovered of
any underdrawing that would have enabled the architect
to fix the dimensions of an individual structure within the
aggregate of its superordinate building site, or the boundaries
of the individual building site within the layout of the
entire Plan. Yet it is obvious that even the most accomplished
architectural draftsman could not assemble such a
variety of different structures into an over-all design of
such complexity without the aid of a guiding underdrawing.
In the absence of underdrawing, the design can only have
been produced by tracing.

Parchment, because of its relative opacity, is not an ideal
medium for tracing; but designs can be traced directly
from one sheet of parchment to another, as may be established
easily by experimentation in any library that is
provided with scraps of medieval manuscripts.[110]

[110]

It cannot be done easily if the two skins are laid flat upon the surface
of a dark table, but can be accomplished without difficulty if they are
held against a windowpane or against a lighted surface reflecting the sun
in sufficient strength to project the design of the original through the
transparent body of the skin above it on which the design is to be redrawn.
I am most grateful to Dr. Johannes Duft for helping me to
establish this fact by superimposing sheets of medieval parchment of
varying thickness from the archives of the monastery of St. Gall and
observing their translucency under different light conditions. To produce
a tracing from an original of some 30½ × 44 inches is nevertheless not an
easy task, even though the tracing was done on three separate sheets. In
order to keep the original under sufficient tension to provide a solid base
for the hand of the copying draftsman and to permit him to move it in
the direction of the required light, it must have been mounted on a
wooden frame. To a medieval scribe the mounting and stretching of
skins on wooden frames was a familiar practice, as it was a standard
procedure in the manufacture of parchment.

(Since these lines were written I have had occasion to experiment
with recently manufactured sheets of parchment, and have been able to
infer from this that fresh parchment is considerably more translucent than
parchment yellowed by age. If the sheets on which the Plan of St. Gall
is drawn were at the time of their manufacture as white and translucent
as modern pieces of parchment of the same thickness, the tracing could
have been produced on a table.)