e.--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. Kneel down again, to
see that all is right, and in the morning draw out the dial-lines; the
string being the gnomon. The true North Pole is distant about 1 1/2
degree, or three suns' (or moons') diameters from the Polar Star, and it
lies between the Polar Star and the pointers of the Great Bear, or, more
truly, between it and [Greek letter] Urs ae Majoris.

[Small drawing illustrating these directions in above text].

The one essential point of dial-making is to set the gnomon truly,
because it ensures that the shadows shall fall in the same direction at
the same hours all the year round. To ascertain where to mark the
hour-lines on the ground, or wall, on which the shadow of the gnomon
falls, the simplest plan is to use a watch, or whatever makeshift means
of reckoning time be at hand. Calculations are troublesome, unless the
plate is quite level, or vertical, and exactly facing south or north, or
else in the plane of the Equinox.

The figure represents the well-known equinoctial sun-dial. It can easily
be cast in lead. The spike points towards the elevated pole, and the rim
of the disc is divided into 24 equal parts for the hours.

Pendulum.--A Traveller, when the last of his watches breaks down, has no
need to be disheartened from going on with his longitudinal observations,
especially if he observes occulations and eclipses. The object of a watch
is to tell the number of seconds that elapse between the instant of
occulation, eclipse, etc., and the instant, a minute or two later, when
the sextant observation for time is made. All that a watch actually does
is to beat seconds, and to record the number of beats. Now, a string and
stone, swung as a pendulum, will beat time; and a native who is taught to
throw a pebble into a bag at each beat, will record it; and, for
operations that do not occupy much time, he will be as good as a watch.
The rate of the pendulum may be determined by taking tw