Collation: 4to: p ² A–G⁴ H², 32 leaves, pp. [iv] 59 [1] (last page blank), engraved title on p 1, engraved arms on divisional title F2, woodcut diagrams in text.
Condition: 194 x 142mm. Light browning, waterstain at the foot of a few leaves of text, single round wormhole in the third leaf of sheets A–D (i.e. it occured before binding) touching a few letters.
Binding: Contemporary limp vellum, inner hinge broken. An attractive copy.
Provenance: Early inscription of Fr. Carlo Flori at foot of title.
References: Riccardi I, 290, 2; Roberts 66–67.
Price: £4000

First edition, first issue without the errata printed on the verso of the last leaf described by Riccardi and found in some copies (e.g. W.P. Watson Catalogue 4, 1993, item 16).
¶ A very attractive copy of the rare first edition of the foundation work of modern hydraulics. Castelli, one of Galileo’s most important pupils, not only extended and disseminated Galileo’s work and methods, but defended him in his two periods of crisis. It was Castelli who persuaded Galileo to transfer the printing of the 1632 Dialogo from Rome to Florence, without which it might never have been published. Castelli was appointed professor of mathematics at the University of Pisa on Galileo’s recommendation.
The fine engraved title is a view of a bridge over the Tiber with a plaque bearing the arms of the dedicatee, Pope Urban VIII.

"In 1628 he published the book Della misura dell’acque correnti, considered to be the beginning of modern hydraulics. Its fundamental propositions related the areas of cross sections of a river to the volumes of water passing in a given time. He also discussed the relation of velocity and head in flow through an orifice. ...
    Some writers have declared that Castelli owed his knowledge of hydraulics to the manuscripts of Leonardo da Vinci and in particular to the compilation of Leonardo’s writings on that subject by Luigi Maria Arconati, now in the Barberini archives. In fact, however, that compilation was dated 1643, and the manuscripts of Leonardo did not pass to the Biblioteca Ambrosiana, where Arconati consulted them, until 1673. Castelli’s correspondence shows quite clearly that his studies of hydraulics were chiefly of an experimental character. It is of interest that he obtained from Galileo the length of an approximate seconds pendulum for use in his experiments and devised a cylindrical rain gauge." (Stillman Drake DSB 3:116a.)