Rebounding Water Mixed with Air; the Wind Circius
Falling water rebounds faster when full of air, and a digression on wind forced through mountain gorges
A pen sketch of turbulent falling water accompanies notes on how water behaves at a cascade. Leonardo states that the rebound of water is faster than the impact when the striking water is thoroughly mixed with air. A second note on the fall and rebound of water breaks off (with a gap in the source) and turns to wind, observing that air escapes upward easily where mountain intervals are wide above and narrow below. He closes with a classical anecdote: Augustus, in Gaul, vowed and built a temple to the wind Circius after a like blast nearly destroyed his army.
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Water rebounds faster than it strikes when mixed with air
Leonardo states that the motion of water's rebound is faster than that of its impact when the striking water is much mixed with air. The accompanying sketch shows the swirling, aerated water thrown up from a fall.
Wind escaping upward through mountain gorges; the Circius wind
Where the intervals between mountains are wide above and narrow below, the wind easily flees upward. Leonardo cites how Augustus, in Gaul, made a vow and built a temple to the wind Circius because a similar blast had nearly cost him his army.