projects. Over time the public and private relationship diminished as the brick business turned into an imperial monopoly. The Romans took their brickmaking skills everywhere they went, introducing the craft to the local populations. The Roman legions operated mobile kilns and introduced bricks to many parts of the empire. The bricks became time records and geographical pinpoints to where the Roman military was operating. Roman bricks are often stamped with the mark of the legion that supervised their production. Roman brick was used to construct famous architecture such as the Red Basilica in Pergamon, Domus Tiberiana and the Basilica of Maxentius in Rome. The use of bricks in southern and western Germany, for example, can be traced back to traditions already described by the Roman architect Vitruvius, although he probably refers to mud brick. In the British Isles, the introduction of Roman brick by the Ancient Romans was followed by a 600–700 year gap in major brick production. When building in masonry, the Romans often interspersed the stonework at set intervals with thin courses of bricks, sometimes known as "bonding tiles". This was done in order to give the structure added stability, and was particularly valuable when building with irregularly shaped building materials such as flint as the bricks would help level up the bed. The practice also had a secondary aesthetic effect of giving a polychromatic appearance to the walls. In the 1530s, the English antiquary John Leland successfully identified Roman bricks (albeit under the misleading designation of "Briton brykes") at several geographically dispersed sites, distinguishing them by size and shape from their medieval and modern counterparts. This has been described as one of the earliest exercises in archaeological typology. Medieval Europe After the Fall of the Western Roman Empire in the 5th century many of the commercial stone quarries in Europe were abandoned. This led to a consistent pattern of reuse of Roman building materials throughout the next several hundred years. Like much of the Roman stone, Roman bricks were gathered for reuse throughout this period. For example, in the 10th century the abbots of St. Albans gathered enough Roman brick during this time period to have their own stockpile of the building material. When brick production resumed in earnest on the British Isles, the 1½" to 2" height of the Roman-style brick gradually increased during the early Medieval period. Brick from the ancient Roman Empire was commonly