1812. PRACTICAL APPLICATION OF ASTRONOMY. 35 
important uses to which the heavenly bodies are applied in modern 
times, and on the essential service which they rendered in former ages 
to the traveller while crossing the trackless sands of Northern Africa. 
That a modern traveller, under circumstances similar to those in 
which I was at this time placed, might derive some advantages from 
them, it will be admitted ; if it be supposed that necessity might 
require him to travel over a plain by night, without instruments, and 
at the same time to keep some account of the direction of his 
route. For by noting that setting star towards which he seems to be 
advancing, the bearing of his track may readily be calculated, or after- 
wards ascertained by a celestial globe, to a degree of exactness quite 
sufficient for such purpose. And this method will be found more 
accurate in proportion as the country is nearer to the equinoctial 
line; but perhaps not sufficiently correct, in those beyond the 
thirtieth or fortieth degree of latitude. Thus the setting of 0 Oriontis^ 
or the north-westernmost star of the belt of Orion, might point 
out to him the west more truly than the polar star does the north. 
But in aid of these advantages, a habit of judging of angular dis- 
tances, would be required whenever the atmosphere should be too 
dense on the horizon, or whenever it became necessary to make use of a 
star not directly in his track. Even the length of time occupied in 
travelling, may be known nearly, if he note what star sets when he 
commences, and what other when he ends, his night's journey. It 
must be confessed that these methods can hold but a low rank in the 
science of practical geometry ; but it is easy to imagine very pro- 
bable circumstances in which they would be exceedingly valuable. 
Srd. We were half-unwilling to quit these delightful pastures ; 
and suffered our cattle to continue grazing the whole morning In 
the mean time our fires had been observed from a great distance by 
a kraal of natives situated on a low hill nearly nine miles farther 
onwards, and in sight from our station. They came immediately to 
see who we were ; and, after cautiously reconnoitring, and perceiving 
that we were accompanied by some natives who were personally known 
to them, they advanced towards us with friendly salutations, and with- 
out hesitation joined our party. There were about eight or ten of 
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