By means of Professor Wheatstone’s apparatus, the Duration
of the Electric Spark has been ascertained not to exceed the
twenty-five-thousandth part of a second. A cannon-ball, if illumined
in its flight by a flash of lightning, would, in consequence of the
momentary duration of the light, appear to be stationary, and even the
wings of an insect, that move ten thousand times in a second, would
seem at rest.