Explorers naturally select hills as their points of
triangulation; but compass observations on hill-tops, if unchecked by a
sextant observation of the sun's bearings, are never so reliable as those
taken on a plain.
[Sketch of card as described on following pages].
Bearings by Sun and Stars.--It requires very great practice to steer well
by stars, for, on an average, they change their bearings even faster than
they change their altitudes. In tropical countries, the zodiacal stars -
as Orion and Antares--give excellent east and west points. The Great
Bear is useful when the North Pole cannot be seen, for you may calculate
by the eye whereabout it would be in the heavens when the "pointers" were
vertical, or due north; and the Southern Cross is available in precisely
the same way. The true North Pole is about 1 1/2 degree or 3 diameters of
the full moon, apart from the Pole star; and its place is on a line
between the Pole Star and the Great Bear. An almanac, calculated to show
the bearing, and the times of moonrise and moonset, for the country to be
travelled over, as well as those of sunrise and sunset, would be a very
great convenience; it would be worth while for a traveller accustomed to
such calculations to make one for himself.
Diagram.--The diagram (preceding page) is intended to be traced in lines
of different colours, when it will be found to be far less confused than
at present.
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