DEATH BY LIGHTNING. 441 



in rapidity that of the rifle-bullet. A flash of light- 

 ning cleaves a cloud, appearing and disappearing in 

 less than a hundred-thousandth of a second, and the 

 velocity of electricity is such as would carry it in a 

 single second over a distance almost equal to that which 

 separates the earth and moon. It is well known that a 

 luminous impression once made upon the retina en- 

 dures for about one-sixth of a second, and that this is 

 the reason why we see a continuous band of light when 

 a glowing coal is caused to pass rapidly through the 

 air. A body illuminated by an instantaneous flash 

 continues to be seen for the sixth of a second after the 

 flash has become extinct; and if the body thus illu- 

 minated be in motion, it appears at rest at the place 

 where the flash falls upon it. When a colour-top with 

 differently-coloured sectors is caused to spin rapidly 

 the colours blend together. Such a top, rotating in a 

 dark room and illuminated by an electric spark, ap- 

 pears motionless, each distinct colour being clearly 

 seen. Professor Dove has found that a flash of light- 

 ning produces the same effect. During a thunderstorm 

 he put a colour-top in exceedingly rapid motion, and 

 found that every flash revealed the top as a motionless 

 object with its colours distinct. If illuminated solely 

 by a flash of lightning, the motion of all bodies on the 

 earth's surface would, as Dove has remarked, appear 

 suspended. A cannon-ball, for example, would have 

 its flight apparently arrested, and would seem to hang 

 motionless in space as long as the luminous impression 

 which revealed the ball remained upon the eye. 



If, then, a rifle-bullet move with sufficient rapidity 

 to destroy life without the interposition of sensation, 

 much more is a flash of lightning competent to pro- 

 duce this effect. Accordingly, we have well-authen- 

 ticated cases of people being struck senseless by light- 



