little training could give them. Without some capacity in this
direction, the student is always at a disadvantage in his contact with
Nature. He can not make a record of what he sees as long as the
element of horizontal and vertical distance is not clearly in mind. To
attain this end the student should begin by pacing some length of road
where the distances are well known. In this way he will learn the
length of his step, which with a grown man generally ranges between
two and a half and three feet. Learning the average length of his
stride by frequent counting, it is easy to repeat the trial until one
can almost unconsciously keep the count as he walks. Properly to
secure the training of this sort the observer should first attentively
look across the distance which is to be determined. He should notice
how houses, fences, people, and trees appear at that distance. He will
quickly perceive that each hundred feet of additional interval
somewhat changes their aspect. In training soldiers to measure with
the eye the distances which they have to know in order effectively to
use the modern weapons of war, a common device is to take a squad of
men, or sometimes a company, under the command of an officer, who
halts one man at each hundred yards until the detachment is strung out
with that interval as far as the eye can see them. The men then walk
to and fro so that the troops who are watching them may note the
effects of increased distance on their appearance, whether standing or
in motion. At three thousand yards a man appears as a mere dot, which
is not readily distinguishable. Schoolboys may find this experiment
amusing and instructive.

After the student has gained, as he readily may, some sense of the
divisions of distance within the range of ordinary vision, he should
try to form some notion of greater intervals, as of ten, a hundred,
and perhaps a thousand miles. The task becomes more difficult as the