666 
the lapse of centuries, so that it is difficult to arrive at any 
accurate measurement of the ditch and vallum. I calculated, 
in a rough way, that the inner rampart would be twenty- 
four feet wide ; the fosse, or ditch surrounding it, twelve 
feet ; the next rampart, or vallum, eighteen feet wide ; then 
a second ditch, twelve feet in width ; and, last, at the 
outside, a narrower and lower vallum. All these ramparts 
appear to rise on a graduated scale. The outer of less height 
than the second ; and the second lower than the inner. 
In front of the principal gate — the Porta Prsetoria — at 
the distance of about 100 feet, is a raised mound, as if it 
were an advanced post to protect the gate.* The distance 
from north to south is, speaking generally, about 700 feet ; 
from east to west, a mean of 240 feet. 
In the rear of the first camp is a second similar enclosure, 
distant about 300 feet from the Porta Decumana. The 
mean average appears to be 400 feet by 200 feet. It has 
only a single vallum and ditch. This I suppose to have 
been the quarters of a second legion. Agricola, in his 
expedition against the Caledonians, was surprised by a 
night attack, and the camp of the ninth legion, which 
was the weakest, nearly overwhelmed, when he came to their 
assistance. 
The remarkable point to be noticed is, how singularly 
perfect and distinct are the raised elevations, or mounds, 
; - " If four legions, or two consular armies, were united and enclosed by the 
same ramparts, their two camps then formed an oblong rectangle, the back of 
each single camp being turned towards the other. . . . The camp had four gates, 
one at the top and bottom. The back gate, 'a& tergo,' was called the Decumana; 
the front gate, the Pretoria ; the gates at the side, Dextra and Sinistra. Camps 
were made square, round, or triangular, to suit the nature of the ground. The 
most approved form was the oblong; length one-third greater than the breadth. 
A distinction was also made between those for a night, on a march, and those 
built more strongly, for stationary purposes." — Smith's Dictionarii of Roman 
A ntiqv ities — " Castra. " 
