sufficient and creditable accuracy.

"Who would not," {59a} says Sir John Herschel, "ask for demonstration
when told that a gnat's wing, in its ordinary flight, beats many
hundred times in a second? or that there exist animated and regularly
organised beings many thousands of whose bodies laid close together
would not extend to an inch? But what are these to the astonishing
truths which modern optical inquiries have disclosed, which teach us
that every point of a medium through which a ray of light passes is
affected with a succession of periodical movements, recurring
regularly at equal intervals, no less than five hundred millions of
millions of times in a second; that it is by such movements
communicated to the nerves of our eyes that we see; nay, more, that
it is the DIFFERENCE in the frequency of their recurrence which
affects us with the sense of the diversity of colour; that, for
instance, in acquiring the sensation of redness, our eyes are
affected four hundred and eighty-two millions of millions of times;
of yellowness, five hundred and forty-two millions of millions of
times; and of violet, seven hundred and seven millions of millions of
times per second? {59b} Do not such things sound more like the
ravings of madmen than the sober conclusions of people in their
waking senses? They are, nevertheless, conclusions to which any one
may most certainly arrive who will only be at the pains of examining
the chain of reasoning by which they have been obtained."

A man counting as hard as he can repeat numbers one after another,
and never counting more than a hundred, so that he shall have no long
words to repeat, may perhaps count ten thousand, or a hundred a
hundred times over, in an hour. At this rate, counting night and
day, and allowing no time for rest or refreshment, he would count one