APPENDIX. 
xliii 
tries in general, there are so many things to obstruct a direct track, 
that, though an animal may actually pass over the ground at the rate 
of three or three and a half miles per hour, as the camel in reality 
does, yet, in estimating the distance for a traverse-table, great 
deductions must be made, or our reckoning will far exceed the 
truth*. 
The journey round the Syrtis having satisfied us with respect to 
the rate which might be allowed, and the accuracy that was to be 
expected under general circumstances, we determined to ascertain 
what precision we could arrive at when the direction of the road and 
nature of the ground were the most favourable. For this purpose we 
kept a track from Bengazi to Ptolemeta ; and having occasion to go 
over the same ground a second time and return, we had three mea- 
surements between the places independent of that of the chronome- 
ters which, as well as those of the intermediate stations, agree 
together and with the truth, to an exactness which we did not 
expect ; and will serve to show that, under favourable circumstances, 
and when attention is paid to the rates of the camels, the topography 
of a country may be laid down sufficiently accurate for most pur- 
poses. We should have informed our readers, that the track from 
Bengazi to Ptolemeta is particularly straight, and encumbered 
with as few obstructions as are likely ever to occur in a country 
where, properly speaking, no road exists. 
* In caravans where the road lies over a wide expanse of desert, and where it is 
the interest of every man to accomplish as much distance in a day as he can, the 
average will of course far exceed that which was made good by our party, 
t See the Table annexed. 
