298 
ASCERTAINING THE COURSE AND DISTANCE. 
29 June, 
put to the waggons without delay, and all were soon ready ta 
depart. 
The magnetic needle was here so much affected by the particles 
of iron contained in the rocks at this station, that it was not to be 
depended on. It was my usual practice at every station, to take the 
bearings of as many of our former stations as were either in sight, 
or of which the situation could be indicated with tolerable exact- 
ness ; and at the same time, those of any other remarkable objects, 
and of our next station forward whenever it was known and could 
be indicated with precision, were noted down. By these means, 
the bearings, being taken both backwards and forwards, gave a 
double check to any inaccuracy which might arise from errors of 
the needle, or from mistaking the position of stations not actually 
in sight. 
In order that this very necessary part of a traveller's duty 
might not, in the confusion of a multitude of heterogeneous occupa- 
tions, be forgotten, these operations were almost always deferred till 
the moment when the oxen were brought forward to be put in the 
yoke; so that I thus became habitually reminded of what was to be 
done, and my men were by the same means prepared for pointing 
out the bearing of these stations and places which were too dis- 
tant to be visible. On such occasions I generally consulted them, 
and placed more or less confidence in their opinions, as these proved 
either unanimous or at variance. 
Fearing that we should not reach our next station before dark, 
we hastened the oxen forward at their best pace, and advanced at the 
rate of eighteen revolutions * in a minute ; which was equal to 3 miles, 
1 furlong, and 170 yards, in an hour. As our road was over deep 
sands, this rate might be considered as very expeditious, for a waggon 
on narrow wheels, heavily laden and drawn by oxen. In some places, 
a black mottled flinty rock, showed itself through the surface of the 
ground. 
* The mode in which this was ascertained, has been already explained at page 289. 
of the preceding volume. 
