sting (together with the notes corresponding to sheet 120 r. -d of the Atlantico Codex) as regards hints at sources which were to prove useful in the studies for the Treatise on water and the discussion of the meteorological and cosmographic questions contained in it. Such notes are believed to date back to the period slightly after Leonardo’s return to Florence – March or April 1500 –, without however entirely excluding the possibility that they may have been written, as suggested by some coincidences, after Leonardo, having left Valentino, had once again set up house in Florence. Certainly Leonardo, stimulated by the memory of the magnificent progress of the Lombard canalisation works and by the desire to apply such progress to Tuscany did not interrupt or quickly resumed after his return home, his elaboration of the Treatise on water, the traces of which are already drawn up in earlier or contemporary manuscripts. However the compilation of the Leicester manuscript may not be dated before his return from the expedition to Romagna. Some memories contained in it which seem personal lead one to deduce a familiarity with those regions which it is not clear on what earlier occasion Leonardo could have acquired: “Li suoli, o ver falde delle pietre, non passano troppo sotto le radici de’ monti, ch’elle (son a) sono di terra (piena da) da far vasi, piena di nichi; e ancora (va) queste vanno poco sotto, che si trova la terra comune, come si vede ne’ fiumi, che scorran la Marca e la Romagnia, usciti delli Monti Appennini, e...» (The subsoil and rocky strata do not run too deeply under the slopes of the mountain and are composed of terra cotta clay and shells. This stratum is only slightly below the normal soil, as can be seen in the rivers flowing in the Marche and in Romagna once outside the Apennine mountains) “Gran somma di nichi si vede, dove li fiumi versano in mare, perché in tali siti l’acque non sono tante salse, per la mistion dell’acque dolci, che con quelle s’uniscano; e ’l segnio di ciò si vede dove per antico li monti Appennini versavano li lor fiumi nel mare Adriano, li quali in gran parte mostrano in fra li monti gran somma di nichi insieme coll’azzurrigno terren di mare; e tutti li sassi, che di tal loco si cafano, son pieni di nichi”. (A large number of