Water or wind striking obstacles at different angles
Every heavy body weighs along the line of its motion
The page opens with the maxim that every heavy body weighs along the line of its motion, then turns to three kinds of obstacle struck by water or wind, sketched as a horizontal line crossed by diagonal bars lettered a c e and h b d f. Leonardo argues that whether the stream h f strikes at a b, c d or e f, all the impacts are of equal value, because a surface met at unequal angles is correspondingly longer than one met squarely, so each receives the full thickness of the water. A small right-angle figure at the lower left is captioned as two rectangles above and below a line, with the note 'proof above'.
On this page
A heavy body weighs along the line of its motion
Leonardo states as a principle that every heavy body exerts its weight along the line of its own motion.
Equal percussion of water or wind on angled surfaces
The line h f may be water or wind; wherever it strikes, at a b, at c d, or at e f, all its impacts are of equal value. A surface a b met at unequal angles is so much longer than the surface e f met squarely that it makes up the difference, so each receives the whole thickness of the water.
Two rectangles and 'proof above'
A small figure of two rectangles, one above and one below a line, is annotated with the words 'proof above', referring the reader back to the argument set out earlier on the page.