The units in which the base is measured may be feet, yards,
minutes, or hours' journey, or whatever else is convenient. Any multiple
or divisor of 100 may be used for the base, if the tabular number be
similarly multiplied. Therefore a traveller may ascertain the breadth of
a river, or that of a valley, or the distance of any object on either
side of his line of march, by taking not more than some sixty additional
paces, and by making a single reference to my table. Particular care must
be taken to walk in a straight line from A to B, by sighting some more
distant object in a line with B. It will otherwise surprise most people,
on looking back at their track, to see how curved it has been and how far
their b' B is from being in the right direction.
[Contains Table for Rough Triangulation without the usual instruments,
and without Calculation"].
Measurement of Time.--Sun Dial.--Plant a stake firmly in the ground in a
level open space, and get ready a piece of string, a tent-peg, and a bit
of stick a foot long. When the stars begin to appear, and before it is
dark, go to the stake, lie down on the ground, and plant the stick, so
adjusting it that its top and the point where the string is tied to the
stake shall be in a line with the Polar Star, or rather with the Pole
(see below); then get up, stretch the string so as just to touch the top
of the stick, and stake it down with the tent-peg.
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