Ellissi e ovali: epilogo di un conflitto

S. Benedetti recently discovered a geometric construction, feasible by a compass, which returns the curve of the intrados of Sr. Peter's dome, in Sangallo 's wooden model, exposed last year in Venice. This construction was examined in a computer environment, comparing the profile of the original dome and an analytically generated ellipsis. It has so been possible to verify that the Benedetti's oval and the ellipsis are close to be perfectly superimposed and that the discards are absorbed by irregularity of the ware. A following investigation of the geometric knowledge of that period has allowed to obtain a construction of this curve which could be called ellipsis-oval or practical ellipsis, and that, although drawn with a compass, is, in fact, nor distinguishable from an ellipsis. This result seems to frustrate the past controversies between the supporters of the two kind of curves as the correct interpretation of classic architecture’s tracing and, instead, it points out the value of a research which consider other elements, like the brick's arrangement, and which observe more carefully the tracing techniques in the design as well as the construction of the building.