it, at a time when the workings of his mind, having reached a considerable degree of complexity, presumed a dense network of connections between the subject areas cultivated by him and permitted certain references to their governing principles. The Leicester manuscript does not contain, unlike the other Vinci codes, dated notes enabling one to deduce the year or years when it was compiled. Only the date of the earthquake which is said to have occurred in “eighty 9”, in other words, 1489 , in the sea of “Satalia” , or Attalia, near Rodi is given. But another citation, more important because personal, may be used despite not offering dates to eliminate the entire decade subsequent to the year now indicated by the range of possible suppositions regarding the period in which the Code was written. Leonardo speaks – sheet 9 verso – of fossils from the mountains of Parma and Piacenza, “de’ quali, quand’io facevo il gran cavallo di Milano, me ne fu portato un gran sacco nella mia fabbrica da certi villani” (of which, when I was making the great horse in Milan a large sack full was brought to me in my workshop by certain peasants); and the memory he has of the work which he had so long awaited hoping to entrust his glory as a sculptor to it, leads one to suppose that an interval of some duration had already passed between the moment of writing and the interruption of that colossal work . Another reason for excluding the years before 1499-1500 may be found by examining the note made by Leonardo on sheet 30 verso, “contro alli mulini di Sancto Nicolò, che non vogliano ostaculo alcuno nella lor gora”, [against the water-mills of San Nicolò, which do not mean to hinder anyone in their mill-race] if, as is probable, there is a connection between this passage and the consultancy which they were to give rise to in 1499 (Florentine style) on account of the concern over the flowing of water from Monte del Re which threatened the church of S. Salvadore, also known as S. Francesco a Monte. To better ascertain the causes of this insidious phenomenon and to prevent it in the future, according to a document divulged by Uzielli , the opinions of various architects had been requested, among them Leonardo da Vinci, who had supplied a design for setting to rights the dangerous part of the mountain, pointing out specifically the defects of the buildings and the conditions of the down flow of the waters . It is probable that the water mills of S. Nicolò did not just use water from the Arno but also the water which came down from Monte del Re or Monte S. Salvadore, above the place where they were situated ; that the millers, fearing that their immediate interests would be affected negatively, had protested in advance against any alteration to the way things were; and that the specious motive of their protest had given Leonardo an opportunity to reproach them and observe, with particular attention to their case, that “l’acqua, che