University of Virginia Library

ANGULAR DISTORTIONS CAUSED
BY A SHIFT IN THE RELATIVE POSITION OF
ORIGINAL AND OVERLAY

My second argument in support of the contention that the
Plan of St. Gall is not an original rests on the observation
that in several areas the drawing exhibits angular distortions
that owe their origin to a shift in the alignment of original
and overlay. This observation is of crucial importance not
only for the question of originality but also because it gives
us a clue for establishing the sequence in which the buildings
were traced. We shall analyze this phenomenon in
detail in a subsequent chapter.[112] For the present discussion,
suffice it to stress that we are faced here with a type of
linear deflection caused in the process of tracing when an
inadvertent shift between original and overlay is not
immediately detected and corrected. These deflections are
unlikely to occur on an original, as the underdrawing
would contain each individual building within the area
assigned to it, and would prevent the parallels from running
askew. The author of the Plan of St. Gall was able to
dispense with an elaborate system of auxiliary reference
lines, since for him the original itself performed the
function of the underdrawing. But as it was delineated on
a different surface, his drawing was subject to displacement
in relation to the original.