Page:The age of Justinian and Theodora (Volume 1).djvu/52

 these towers serve as guard-houses, and the sentries are enjoined to maintain their vigilance by passing the word of each successive hour from post to post during the night. The usual thickness of this wall is about eight feet, but no regular rampart has been prepared along the summit, the defensive value of such an area being superseded by the peribolos. Hence the top, the width of which is limited to less than five feet by the encroachment of the parapet, has no systematic means of access from the ground or from the towers. Hewn stone, worked in the vicinity, has been used for the construction of these fortifications, and in some places close to the city the ground may be seen to have been quarried into hills and hollows for the supply of the builders. *