1006.

They do not know why the Arno will never remain in a channel.  It is because the rivers which flow into it deposit earth where they enter, and wear it away on the opposite side, bending the river in that direction.  The Arno flows for 6 miles between la Caprona and Leghorn; and for 12 through the marshes, which extend 32 miles, and 16 from La Caprona up the river, which makes 48; by the Arno from Florence beyond 16 miles; to Vico 16 miles, and the canal is 5; from Florence to Fucechio it is 40 miles by the river Arno.

56 miles by the Arno from Florence to Vico; by the Pistoia canal it is 44 miles.  Thus it is 12 miles shorter by the canal than by the Arno.

[Footnote:  This passage is written by the side of a map washed in Indian ink, of the course of the Arno; it is evidently a sketch for a completer map.

These investigations may possibly be connected with the following documents. Francesco Guiducci alla Balia di Firenze.  Dal Campo contro Pisa 24 Luglio 1503 (Archivio di Stato, Firenze, Lettere alla Balia; published by J. GAYE, Carteggio inedito d’Artisti, Firenze 1840, Tom.  II, p. 62):  Ex Castris, Franciscus Ghuiduccius, 24. Jul. 1503. Appresso fu qui hieri con una di V. Signoria Alexandro degli Albizi insieme con Leonardo da Vinci et certi altri, et veduto el disegno insieme con el ghovernatore, doppo molte discussioni et dubii conclusesi che l’opera fussi molto al proposito, o si veramente Arno volgersi qui, o restarvi con un canale, che almeno vieterebbe che le colline da nemici non potrebbono essere offese; come tucto referiranno loro a bocha V. S.

And, Archivio di Stato, Firenze, Libro d’Entrata e Uscita di cassa de’ Magnifici Signori di luglio e agosto

1503 a 51 T.:  Andata di Leonardo al Campo sotto Pisa.  Spese extraordinarie dieno dare a di XXVI di luglio L. LVI sol.  XII per loro a Giovanni Piffero; e sono per tanti, asegnia avere spexi in vetture di sei chavalli a spese di vitto per andare chon Lionardo da Vinci a livellare Arno in quello di Pisa per levallo del lilo suo. (Published by MILANESI, Archivio Storico Italiano, Serie III, Tom.  XVI.} VASARI asserts:  (Leonardo) fu il primo ancora, che giovanetto discorresse sopra il fiume d’Arno per metterlo in canale da Pisa a Fiorenza (ed.  SANSONI, IV, 20).

The passage above is in some degree illustrated by the map on Pl.  CXII, where the course of the Arno westward from Empoli is shown.]

1007.

The eddy made by the Mensola, when the Arno is low and the Mensola full.

[Footnote:  Mensola is a mountain stream which falls into the Arno about a mile and a half above Florence.

A=Arno, I=Isola, M=Mvgone, P=Pesa, N=Mesola.]

1008.

That the river which is to be turned from one place to another must be coaxed and not treated roughly or with violence; and to do this a sort of floodgate should be made in the river, and then lower down one in front of it and in like manner a third, fourth and fifth, so that the river may discharge itself into the channel given to it, or that by this means it may be diverted from the place it has damaged, as was done in Flanders—­as I was told by Niccolo di Forsore.