Having freed the field of the possible deductions regarding the years prior to 1503, one must then compare the Leicester Codex to the other manuscripts, and to the history of Leonardo’s ideas to try and whittle down the period in which the Codex may have been written: a period which Richter gives as ranging from 1500 to 1516 (with a question mark over 1510 and which should here and now be reduced within narrower limits. In fact, starting from the end of 1510, when Leonardo was busy reaping the fruits of his anatomical studies with Marco Antonio Della Torre, a definite change to the opinion expressed on various occasions in the Leicester manuscript regarding the circulation of water in the world, compared by him with rigid parallelism to the circulation of blood in animals, shows us that Leonardo had changed his way of thinking in a certain and definitive manner, as one may infer not just from the blunt expression of the passage quoted, but also from later notes belonging to the manuscript G. When Leonardo contradicted – in the Anatomical sheets – what he had so carefully sustained in the Leicester manuscript, he had already been in Milan for at least two years, that is presumably since the spring of 1508. For the reasons already cited, which induce one to believe that the Codex was compiled mainly in Florence, further investigation would seem to rule out any time later than 1508. It is to this year that the first sheets of the Arundel Codex must refer, and, to the subsequent months, the manuscript F, which offer, the former and the latter, considerable coincidences with the Leicester manuscript and, specifically, with the last two sheets of this Codex.