TRIPOLY TO BENGAZI. 
141 
It is difficult to fix any precise date to these buildings, but we 
may perhaps conclude, with some appearance of reason, that the 
greater number of them were erected by the Eomans under the 
emperors, who possessed, at various times, the whole of the north 
coast of Africa, and kept open an extensive communication along 
the shores of the Mediterranean, as well as with some parts of the 
interior *. The quadrangular form of these structures is the same 
as that used by the Komans in their stations and encampments ; and 
the small number of troops which was allotted by the empire for the 
defence of Africa, made it peculiarly necessary that their garrisons 
should be well intrenched -f-. It has been calculated that a square of 
seven hundred yards was sufficient, according to the Roman method 
of encampment, for containing a body of twenty thousand men ; and 
a square of one hundred feet would, at that rate, suffice for the accom- 
modation of nine hundred and fifty. The habitable parts of the forts 
above mentioned very rarely exceeded a square of that size, and this 
portion of the structure, in by far the greater number of them, seldom 
* The tower of Euphrantas is however stated to have been a boundary fort under 
the Ptolemies; and the fortress of Automala, at the bottom of the gulf, is mentioned 
by Diodorus to have been in existence before the occupation of Gyrene by the first of 
those princes. — See Strabo, lib. 17, and Diod., lib. 20. 
f “ With regard to Egypt, Africa, and Spain, (says Gibbon, in describing the 
distribution of the Roman forces,) as they were far removed from any important 
scene of war, a single legion maintained the domestic tranquillity of these great pro- 
vinces.” 
“ We may compute (says the same writer) that the legion, which was itself a 
body of six thousand eight hundred and thirty-one Romans, might, with its attendant 
auxiliaries, amount to about twelve thousand five hundred men.” 
