The 4th International Laboratory for the History of Science
Art, Science and Techniques of Drafting in the Renaissance

Protocol Thursday, 31 May 2001
(by Simona Cremante, Fabio Frosini and Giovanni Masucci)

Romano Nanni introduces the session in the Leonardian Library in Vinci .

Carlo Pedretti proposes to analyze Leonardo's preparatory drawings for the Battaglia di Anghiari to introduce the topic of the horizon in painting and in scientific sketches and notes.
He presents the first sheet of Madrid Codex II which bears the date of June 1504 in Leonardo's hand. This document refers to the time when Leonardo was working on the cartoon for the mural painting and was confronted with the problem of the focal point and lateral distortion. Leonardo seems to have found a solution by creating a centripetal movement in the overall composition. In addition to the sketches of the different episodes Pedretti considers some diagrams investigating the variation of visual angles.

Discussion - Discussion - Questions are raised on the subject of the distinction between the empirical and theoretical nature of Leonardo's drawings and diagrams and on the legitimacy of such a distinction.
The developement of the debate leads to the key term of sperientia (experience) used by Leonardo himself to define his personal aptitude in dealing with science and technique.

Carlo Pedretti goes on to describe two newly discovered fragments, formerly attributed to Stefano della Bella which he now ascribes to Leonardo. One of these shows a representation of a section of circle bearing a note referring to "curvità rettitudine secondo il centro del mondo" (curvature straight line according to the center of the world). Pedretti compares this fragment to folios 14v-15r of Manuscript K¹ in the Institut de France, where we can find a very similar inscription and sketch: "Curva retta secondo il centro del mondo" (curve straight according to the center of the world). The second fragment illustrates the last scene of Poliziano's Orpheus with small figures recalling those of the Battaglia di Anghiari.
In 1583 Giovan Paolo Lomazzo records the special anamorphic features of Leonardo's horse drawings for King Francis I. Also Girolamo Figino states Leonardo's ability in anamorphical drawings. Pedretti underlines Leonardo's preoccupation with the representation and definition of the horizon when he was in France

Vladimiro Valerio provides a critical survey of the last section of Leonardo's Book of Painting dedicated to "the horizon". He praises the innovative aspects which are here introduced with relation to the astronomical and perspectival tradition. According to the analysis made by Valerio the concept of the horizon includes several disciplines which range from linguistics to astronomy, geodetics, geometry, perspective, painting and optics. He stresses the use of the term and the concept of "infinity" by Leonardo.
He continues with a very detailed analysis of the sketches and notes and the criteria of demonstration employed by Leonardo. Valerio shows that in the famous Durer engraving, in which he illustrates the prospectographer, the artist's eye is higher than the line of the horizon, as Leonardo illustrates in his notes.

Carlo Pedretti quotes from Book of Painting § 936, Leonardo's poetic description of the Egyptian horizon: "Molto distante è l'orizzonte che si vede nel lito del mare d'Egitto."

Rocco Sinisgalli explains folio 366v from the Codex Atlanticus as containing Leonardo's geometric construction of the parabola. This parabola is represented using the cross section of the visual pyramid. He then deals with Codex Atlanticus, 318r, where is clearly illustrated the construction of an ellipse as the cross section of a cylinder.

Filippo Camerota illustrates a series of clever instruments such as compasses and "seste" and other drawing devices, e.g. pantographs, to obtain representations of epicycloids, parabolas or similar geometric figures. He suggestes a very different reading of the parabola in folio 366v from the Codex Atlanticus, as based on an empirical-technical procedure rather than on a theoretical geometrical construction.

Discussion - All the scholars, junior and senior, join in to share impressions, comments, complaints on the present Laboratory and to make suggestions for the future.