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been able to testify that no pain was felt prior to the loss
of consciousness.

The time required for a rifle-bullet to pass clean through
a man’s head may be roughly estimated at a thousandth of
a second. Here, therefore, we should have no room for
sensation, and death would be painless. But there are
other actions which far transcend in rapidity that of the
rifle-bullet. A flash of lightning 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 oneésixth of a second, and that this is the
reason why we see a ribbon of light when a glowing coal
is caused to pass rapidly through the air. A body illumi-
nated 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 illuminated be in motion, it appears at
rest at the place where the flash falls upon it. The color-
tOp is familiar to most of us. By this instrument a disk
with differently-colored sectors is caused to rotate rapidly;
the cOlors blend together, and, if they are chosen in the
proper proportions, when the motion is sufficiently rapid
the disk appears-white. Such a top, rotating in a dark room
and illuminated by an electric spark, appears motionless,
each distinct color being clearly seen. Professor Dove has
found that a flash of lightning produces the same effect.
During a thunder-storm he put a color-top in exceedingly
rapid motion, and found that every flash revealed the top
as a motionless object with its colors 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 motion-

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