The river Loire at Amboise.
The river is higher within the bank b d than outside that bank.
The island where there is a part of Amboise.
This is the river that passes through Amboise; it passes at a b c d, and when it has passed the bridge it turns back, against the original current, by the channel d e, b f in contact with the bank which lies between the two contrary currents of the said river, a b, c d, and d e, b f. It then turns down again by the channel f l, g h, n m, and reunites with the river from which it was at first separated, which passes by k n, which makes k m, r t. But when the river is very full it flows all in one channel passing over the bank b d. [Footnote: See Pl. CXV. Lines 1-7 are above, lines 8-10 in the middle of the large island and the word Isola is written above d in the smaller island; a is written on the margin on the bank of the river above 1. I; in the reproduction it is not visible. As may be seen from the last sentence, the observation was made after long study of the river’s course, when Leonardo had resided for some time at, or near, Amboise.]
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.