Suppose some one should ask you, "What is an hour?" Your answer
might be, "It is the interval marked off by the clock-hand between 1
and 2." "But what if your clock is running down or speeding up?" To
this you would probably reply, "The clock is set and corrected by
the earth, the sun and the stars, which are constant in their
movements." _But they are not_. The earth is known to be running slow,
by reason of tide friction, and this is likely to continue until it
will revolve on its axis, not once a day, but once a year,
presenting always the same face to the sun.

We can only measure time by _uniform_ motion. Observe the vicious
circle. Uniform motion means the covering of equal spaces in equal
times. But how are we to determine our equal times? Ultimately we
have no other criterion save the uniform motion of the clock-hand or
the star dial. The very expressions, "uniform motion," "equal times,"
beg the whole question of the nature of time.

Let us then, in this predicament, consider time not from the
standpoint of experiment, but of conscious experience--what Bergson
calls "real duration."

Every point along the line of memory, of conscious experience, has
been traced out by that unresting stylus we call "the present moment."
The question of its rate of motion we will not raise, as it is one
with which we have found ourselves impotent to deal. We believe on
the best of evidence that the conscious experience of others is
conditioned like our own. For better understanding let us have
recourse to a homely analogy: let us think of these more or less
parallel lines of individual experience in the semblance of the