Perspective and Motion: Moving Light and a Swinging Weight
Why a whirled ember draws a circle of fire; a weight's rise and swing
Two studies of motion and perception. The first, headed 'Perspective and motion,' argues that a swiftly moving body seems to tint its whole path with its own color—a lightning bolt reads as a luminous snake, a whirled ember as a circle of fire—because the eye's receiving faculty is quicker than the judgment. The second, with a semicircular diagram lettered m, a, b, c, d, e, f, g, treats a weight let fall to e that rises again toward b, its angles of swing shrinking together with their arcs.
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A moving light tints its whole path
Every rapidly moving body appears to tint its path with the likeness of its color. A lightning bolt among dark clouds looks like a luminous snake, and a whirled burning ember like a circle of fire, because the imprensiva, the receiving faculty, is more rapid than the judgment.
A weight let fall rises to equal height
If the weight a is let fall toward e, it rises as high toward b, and with as much speed, as a ball of like quality falling along line a b. All the angles b, g, e, d, and c grow smaller one than the next in the same degree as the arcs of their swings shorten.