A River Deflected at Its Bank; the Cimitrilla's Throw
How a current turns at a right-angled bank, and how to aim a small throwing engine
Two studies share the page. In the first, a river striking straight against the opposite bank between two right angles splits and turns, its line of motion bending more sharply toward whichever side runs faster (marked n m); the small upper drawing shows the current meeting the bank. In the second, Leonardo explains how to set a cimitrilla, a light throwing engine: hold it more oblique (position n) to hurl a projectile farther sideways, or oppositely oblique (position g f) to send it higher. A fan of trajectory arcs launched from a single point, labelled r, n and o, illustrates the varying casts.
On this page
A current bending where it meets a right-angled bank
Leonardo considers a river whose straight course strikes the opposite bank between two right angles, then divides part to the right and part to the left. The line of motion bends more crookedly to the right than to the left in proportion as the right-hand part moves faster, the deflection marked n m. The upper sketch shows the stream meeting the bank.
Aiming the cimitrilla: farther across or higher up
For the cimitrilla, a small hurling engine, the more you want it to throw far sideways the more obliquely you hold it, as at n; if you want it to throw higher, hold it in the opposite obliquity, as at g f. The labels f a - n g fix the two settings of the arm.
Fan of trajectories from a single launch point
Below the text a spray of curved trajectories rises from one point, spreading into arcs of different reach and height. The paths are keyed with the letters r, n and o, matching the more-oblique and less-oblique settings discussed for the engine.