by whatever
unit they may be expressed; but, primarily, time can only be measured
by a standard actually or apparently in motion. Absolutely accurate
mean local time, varying, as it does, by infinitesimal differences at
every point in the circuit of the earth, may be shown on a stationary
object, but cannot in general be kept by an individual or object in
motion. The mean local time of some fixed point in each locality must
be taken as the standard for practical use. The important question to
be determined is, over what extent of territory, measuring east and
west from such fixed point, its mean time may be employed for all
ordinary purposes without inconvenience. This can be absolutely
determined only by practical experience.

Careful study of this phase of this subject led, perhaps, more
directly than any one single cause, to the proposal of the detailed
system of standard time which now satisfactorily controls the
operations of one hundred and twenty thousand miles of railway in the
United States and Canada, and governs the movements of fifty millions
of people.

Before the recent change there were a number of localities where
standards of time were exclusively employed which varied as much as
thirty minutes, both on the east and the west, from mean local time,
without appreciable inconvenience to those using them. From this fact
the conclusion was inevitable that within those limits a single
standard might be employed. The result has proved this conclusion to
have been well founded.

No public reform can be accomplished unless the evil to be remedied
can be made plainly apparent. That an improvement will be effected
must be clearly demonstrated, or the new status of affairs which will
exist after the change, must be shown to have been already
successfully tried. Here, as in law, custom and precedent are all
powerful. It would be a difficult task to secure the general adoption
of any system of time-reckoning which cannot be employed by all
classes of the community. Business men would refuse to regard as a
reform any proposition which introduced diversity where uniformity now
exists, nor would railway managers consent to adopt for their own use
a standard of time not coinciding with or bearing a ready relation to
the standard employed in other business circles. To adopt the time of
a universal day for all transportation purposes throughout the world,
and to use it collaterally with local time, would simply restore