Weights in Water, a Potter's-Wheel Clock, and Waves
Buoyant equilibrium, an instrument for measuring speed, and wind-driven waves
The page opens with four small figures of weights (labelled a b, c d, e f, g h) held between the surface and bed of a body of water, and argues that a weight resting at the water level equals as much water once the levity of the air beneath it is counted. A central drawing shows a potter's wheel converted into an instrument for measuring travel: by smearing it with turpentine, marking where falling sand sticks, and counting revolutions against a 'harmonic time', Leonardo computes speed in miles per hour. A closing note 'On waves' observes that waves and wind can each outrun the other, since a wave started by a great wind keeps its impetus after the wind drops. The dense mirror-script margins hold further remarks tied to these figures.
On this page
A weight suspended between the water's surface and its bed
A weight (figures a b, c d, e f, g h, marked aria/peso) is set between the surface and the bottom of the water, coming to rest at a fixed height above the floor of the deep. Set at the water level, the weight is made equal to an equal quantity of water once the levity of the air beneath, which holds it up, is reckoned.
A potter's wheel turned into an instrument to measure speed
Take the potters' wheel (labelled m n) and set on it an instrument whose centre lies over a circular line turning exactly 5 braccia, the diameter being one braccio and 12/221. Smeared with turpentine and turned uniformly against a harmonic time, the sticking sand marks the revolutions; two turns over ten braccia yield a mile in three hundred times, and an hour of 1080 times gives about 3 miles per hour.
On waves: their speed compared with the wind
Sometimes the waves outrun the wind and sometimes the wind is much faster than the wave, as ships at sea prove. Waves can be faster than the wind when they were started by great winds that have since dropped, the wave still retaining great impetus.