On the Motion and Measurement of Water

of gravity on bodies at rest or in motion: the application of the principle of virtual velocitiesA fundamental concept in mechanics where the work done by all forces during an infinitesimal displacement is zero for a system in equilibrium; Leonardo anticipated this principle centuries before it was formally defined. to many cases that advanced mathematics has generalized in our own day. In optics, he described the so-called original: "camera ottica" camera obscura before Porta Giambattista della Porta (1535–1615), often credited with the invention of the camera obscura, though Leonardo's notes prove he understood it much earlier.: he explained, before Maurolico Francesco Maurolico (1494–1575), an Italian mathematician and astronomer who studied optics., the shape of the sun's image through a polygonal aperture: he taught us aerial perspective: the nature of colored shadows: the movements of the iris: the effects of the duration of visible impressions, and many other phenomena of the eye that are not found in Witelo original: "Vitellione." Witelo was a 13th-century Polish friar whose work on optics was a standard text for centuries.. In short, Leonardo had not only observed all that Castelli Benedetto Castelli (1578–1643), a mathematician and student of Galileo. wrote a century after him on the motion of waters, but it seems to me further that the former has in this area surpassed the latter, whom Italy has nonetheless considered until now as the founder of HydraulicsThe branch of science and engineering concerned with the mechanical properties of liquids..

The work that now for the first time sees the light of day confirms, in my opinion, what Venturi asserts. The manuscript of the aforementioned work exists in Rome in the Barberini Library, and I have been able to obtain a copy of it by means of the most distinguished Dr. Francesco Tassi, a resident member of the original: "Accademico residente della Crusca" Accademia della Crusca and former librarian to His Imperial and Royal Highness the Grand Duke of Tuscany, in whose possession is found a codex by Leonardo himself, entitled = Treatise on the nature, weight, and motion of waters, and observations on the course of rivers, which he has courteously offered to me for the purpose of publishing it.

In sending this work to the press, I have believed it necessary to adhere faithfully to the manuscript, and without correcting any