--Actual measurement with the rudest makeshift, is
far preferable to an unassisted guess, especially to an unpractised eye.
Natural Units of Length.--A man should ascertain his height; height of
his eye above ground; ditto, when kneeling: his fathom; his cubit; his
average pace; the span, from ball of thumb to tip of one of his fingers;
the length of the foot; the width of two, three, or four fingers; and the
distance between his eyes. In all probability, some one of these is an
even and a useful number of feet or inches, which he will always be able
to recollect, and refer to as a unit of measurement. The distance between
the eyes is instantly determined, and, I believe, never varies, while
measurements of stature, and certainly those of girth of limb, become
very different when a man is exhausted by long travel and bad diet. It is
therefore particularly useful for measuring small objects. To find it,
hold a stick at arm's-length, at right angles to the line of sight; then,
looking past its end to a distant object, shut first one eye and then the
other, until you have satisfied yourself of the exact point on the stick
that covers the distant object as seen by the one eye, when the end of
the stick exactly covers the same object, as seen by the other eye. A
stone's throw is a good standard of reference for greater distances.
Cricketers estimate distance by the length between wickets.
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