Suddenly cautious, though from what motive he would have been at that moment hardly able to explain, he remained in the concealment of the trees and bushes, until the guard had passed onward; then he cautiously emerged from the place; and, retiring to some distance, fell into a train of earnest and absorbing thought.
To account to the reader for the phenomenon which now engrossed the Pagan's attention, it will be necessary to make a brief digression to the history of the walls of Rome.
The circumference of the first fortifications of the city, built by Romulus, was thirteen miles.

The greater part, however, of this large area was occupied by fields and gardens, which it was the object of the founder of the empire to preserve for arable purposes, from the incursions of the different enemies by whom he was threatened from without.

As Rome gradually increased in size, its walls were progressively enlarged and altered by subsequent rulers.

But it was not until the reign of the Emperor Aurelian (A.D.

270), that any extraordinary or important change was effected in the defences of the city.