Travelling , as performed by Camels. 133 
But to fhew that this difference arofe chiefly from the varia- 
tions in the route acrofs the chaldean desert (between' 
Mesjid Ali and Buffo rah ; fee the annexed fketch, Tab. III.), I 
jfhall proceed, firft, to explain that part of the fubjed ; and 
afterwards to exhibit the particulars in proof. 
Mesjid Ali (or Ali’s Mofque) is fituated at about two thirds 
of the diftance, and as nearly as poflible in the line of direction, 
between Aleppo and Bufiorah ; and is a fort of land-mark to 
the caravans which pafs the common boundary of the Arabian 
and Chaldean deferts. Its geographical pofition is deduced 
from bearings and latitudes taken by M. Niebuhr and others : 
and therefore, as far as general geography is concerned, it 
may almofl: be regarded as a fixed point. Not that the truth of 
its pofition will in any fhape affed the prefent head of enquiry ; 
which is entirely direded towards a companion of the fpaces 
of time, employed between certain points of the route, by each 
traveller refpedively. 
Now, that portion of the Defert route between Mesjid Ali 
and Bufiorah, being fubjed to great variation in the track, as 
appears by the journals of different travellers; whilfl: the much 
larger portion of it, between Mesjid Ali and Aleppo, is very 
nearly the fame at all times ; it is very clear, that this latter 
portion furnifhes the propereft ground on w'hich to form the 
comparifon : and the particulars are as follow : 
Aleppo 
