past. It is by no means
strictly correct to say that memory ever reinstates the past. It is more
true to say that we see the past in retrospect as greatly foreshortened.
Yet even this is hardly an accurate account of what takes place, since,
when we look at an object foreshortened in perspective, we see enough to
enable us imaginatively to reconstruct the actual size of the object,
whereas in the case of time-perspective no such reconstruction is even
indirectly possible.

It is to be added that this constant error in time-reproduction is
greater in the case of remote periods than of near ones of the same
length. Thus, the retrospective estimate of a duration far removed from
the present, say the length of time passed at a particular school, is
much more superficial and fragmentary than that of a recent
corresponding period. So that the time-vista of the past is seen to
answer pretty closely to a visible perspective in which the amount of
apparent error due to foreshortening increases with the distance.

In practice, however, this defect in the imagination of duration leads
to no error. Although, as a concrete image answering to some definite
succession of experiences a year is a gross misrepresentation, as a
general concept implying a collection of a certain number of similar
successions of experience it is sufficiently exact. That is to say,
though we cannot imagine the _absolute_ duration of any such cycle of
experience, we can, by the simple device of conceiving certain durations
as multiples of others, perfectly well compare different periods of
times, and so appreciate their _relative_ magnitudes.

Leaving, then, this constant error in time-appreciation, we will pass to
the variable and more palpable errors in the retrospective measurement
of time. Each person's experience will have told him that in estimating
the distance of a past event by a mere retrospective sense of duration,
he is liable to extraordinary fluctuations of judgment. Sometimes when
the clock strikes we are surprised at the rapidity of the hour. At other
times the timepiece seems rather to have lagged behind its usual pace.
And what is true of a short interval is still more true of longer
intervals, as months and years. The understanding of these fluctuations
will be promoted by our brief glance at the constant errors in
retrospective time-appreciation.

And here it is necessary to distinguish between the sense of duration
which we have duri