The Blow in indivisible time; weighing bodies in water
Concave mirror and sun, buoyancy of iron and wood, the broad sword, and the magnet balance
The page opens with three aphorisms on percussion: the same power concentrated into a briefer time is stronger; a blow occurs in indivisible time and so is incomparable to any timed action; and a power gathered into a smaller place strikes harder, like a concave mirror focusing the sun. A balance experiment (the figure labelled 'acqua') records that iron loses 2/11 of its weight in water while wood loses its whole weight, and that a body suspended in air weighs more than one in water. Further notes observe that a broad sword swung flat feels heavier than swung edge-on, and that an iron needle magnetised and hung between two lodestone weights leans toward the heavier one.
On this page
A blow occurs in indivisible time
A blow is caused in indivisible time, and so is incomparable to any other natural or accidental action made with time; and the same power concentrated into a briefer action has greater strength.
The concave mirror focusing the sun
Among powers of equal quality, the one wholly employed in a smaller place damages its object more — as with the concave mirror and the sun.
Weighing iron and wood in water
Iron placed in water loses 2/11 of the weight it showed in air, while wood loses its whole weight. It was found by experiment that 9 in air balances 11 in water when the weights are in equilibrium, and that some waters sustained 5 against 4 in air.
A body weighs more in air than in water
Of two equal weights hung at equal distance from the pole of a balance, one in water and one in air, the one in air shows itself heavier than the one in water by as much as the water is heavier than the air.
A broad sword swung flat seems heavier
Among bodies of equal material and weight, the one of broader shape appears heavier, as is shown by a sword swung through the air flat-wise versus edge-wise.
Magnetised iron between two lodestone weights
If an iron tempered with the lodestone is set equally distant in the middle between doubled weights of that lodestone, the iron's point leans nearer to the larger piece in proportion as it is of greater power than the other.