Collegonzi, Capraia, Monte Albano, extending on the one side towards Val di Nievole, and a short distance away, on the other side of the Arno, to the Golfolina stone, Montelupo and San Miniato al Tedesco. Leonardo is also most precise in speaking of the geological events of the area between Arezzo and Florence. But, more than the observations recalled here, which one can certainly not attach a decisive value to, it seems that Leonardo’s presence in Tuscany at the time of the compilation of the Leicester manuscript is confirmed by those margin illustrations which very often provide the propositions of the text with examples taken from observations of the Arno and its affluents. These are the sketches, drawn with precise references which may be found on sheets 13 r. (“Ponte Rubaconte. – Below the Bisticci and Cani (ge) giani.10 – Above the Pescaia della Giustizia. – a b is a sandbank, opposite where the isle of Cocomeri finishes in the middle of the Arno), 15 r. (Rifredi, Arno. – Mugnone, Arno. – Ombrone), 16 v. (Above the Rubaconte bridge, at Torricella. – Below the Ceppo hospital), 18 v. (Concavity produced by Mensola, when Arno is low and Mensola full. Arno, Mensola, Mug[n]one, Pesa, Isola”). These sketches and notes are found in the “7 charts” corresponding to sheets from 18-19 to 12-25, containing the first and numerically most important group of “casi d’acque e di sua fondi”; (cases of waters and their depths) and the choice and specific detail of these characteristic examples has no equivalent in the manuscript, for Lombardy. Another note which may be linked to the occupations and studies of Leonardo in Florence after 1500, is this very brief one: “To’ la Ramondina”, which must be ascribed, as we shall see, to the search for or use of a scientific work; and recalls a similar and probably earlier note: “Cerchi in Firenze della Ramondina” (Look for the Ramondina in Florence) The sheet containing this note, in the Arundel Codex, may belong to the same period of activity, reflected in the memoranda of the folio preceding it, it too particularly intere-