Leonardo da Vinci. Del moto e misura dell’acqua. Libri nove ordinati da Fra Luigi Maria Arconati, editi sull codice archetipo barberiniano a cura di E. Carusi ed A. Favaro. Bologna. Nicola Zanichelli editore. 1923. XXIV+412 pp.

Leonardo da Vinci. On the Motion and Measure of Water.

The treatise “On the Motion and Measure of Water” was compiled in 1643 from Leonardo’s manuscripts by the Dominican monk Luigi Maria Arconati. Its basis was the collection of Leonardo manuscripts preserved in the family of the Counts Arconati in Milan. The manuscript of the treatise has come down in two copies differing little from one another, in the Vatican Library and in the National Library of Naples, and was first published, in a very imperfect form, in 1826 by F. Cardinali in Raccolta di autori italiani che trattano del moto delle acque. The new, excellent edition, published by the Vincian Institute in Rome, has been carefully collated not only with the manuscripts of the treatise, but also with Leonardo’s original manuscripts. Parallel to the text of the treatise, wherever possible, the corresponding passages from Leonardo’s codices and Leonardo’s original drawings are reproduced in full. The illustrations

of the main text are reproductions of the drawings in the Vatican manuscript. The editors refrained from any commentary or notes to the text and confined themselves solely to a careful collation of the texts.

A comparison of the texts of Leonardo and Arconati shows that, on the whole, the compiler treated the original rather carefully, limiting himself chiefly to developing certain proofs of Leonardo and to systematization—admittedly a very imperfect one. The editors believe that Arconati also had at hand manuscripts now lost. On the other hand, it is almost beyond doubt that many manuscripts of hydraulic content remained unknown to Arconati. In any case, the published treatise is a conscientious attempt to systematize Leonardo’s hydraulics.

The contents of the treatise are divided into 9 books: 1. On the watery sphere; 2. On the motion of water; 3. On the water wave; 4. On the eddies (retrosi) of water; 5. On falling water; 6. On the destructions produced by water; 7. On objects carried away by water; 8. On the quantity of outflowing water (Dell’onza dell’acqua) and on pipes; 9. On mills and other water machines.

Leonardo’s knowledge and methods, to the great misfortune of science, had almost no influence on its development. Leonardo’s name is not a sequential link in the history of science, but a parallel, almost independent branch. Of course, ancient hydrostatics served as the basis of Leonardo’s hydraulics, but he perceived it in his own way, and it is presented as something new. There are also many errors in the treatise—for example, the design of a perpetual-motion machine based on Archimedes’ law (p. 356). There are many contradictions in the doctrine of wave motion. But here, too, there is an entirely clear concept of the velocity of wave motion, of the principle of superposition of waves; he points to the distortion of the form of a wave surface in the case of a stone thrown into flowing water (the beginnings of the Doppler principle), and so on. Complex cases of unsteady flow are studied experimentally by Leonardo (Book 4); for observing currents he uses the stirring up of millet in water. In many places the text and drawings of the treatise astonish the reader by their modernity. Before us is not the verbose, ornate scholastic dissertation of the sixteenth or seventeenth century, but a living reflection of Leonardo’s eternally youthful experience and sober mind.

S. Vavilov.