This Codex is, among the currently known manuscripts of Leonardo da Vinci, the most notable document of the work which the genius, gathering from innumerable notes and recollections the scattered materials which could go to make up a Treatise, reviewing the topics dealt with, enriching them with new observations, multiplying and developing his ideas as he went, he was preparing to draw from the notes he had accumulated and from his inexorable treasure of real experience an “opra ordinata” for each of the sections of the scientific encyclopaedia which he seems to have applied himself to. In a more comprehensive manner than the others, this notebook shows